10. Microbiology Flashcards
What is microbiology?
Microbiology is the study of organisms that are too small and are not visible clearly to the naked eye or un-aided eye when they exist individually
What are microorganisms?
organisms that are too small and are not visible clearly to the naked eye or un-aided eye when they exist individually
What do microorganisms include?
Bacteria
Archaea
Cyanobacteria/Blue green bacteria (BGB)
Fungi
Protists
Mollicutes such as mycoplasmas and phytoplasmas
Viruses
Viroids
Prions
What is the size of microorganisms?
Generally less than 0.1 mm in size and cannot be observed with a unaided eye
Why are microorganisms observed with a microscope?
Because they cannot be observed with a unaided eye
How are the structural components of microorganisms measured?
In micrometers and nanometers
Why are some microorganisms more readily visible than the others?
Because of their larger size
Why are microorganisms ubiquitous?
because they are found in water, soil, air and interior and exterior surfaces of other organisms
What do marine and freshwater microorganisms form?
The basis of food chains in oceans and freshwaters
Some of them do photosynthesis and are primary producers in aquatic environments
What do soil microorganisms help?
Recycling of chemical elements between soil, water, air and living organisms
How are microorganisms suspended in the air?
as bioaersols
How do bioaersols spread?
They have the opportunity to travel long distances with the wind current and precipitate
Pathogenic bioaerosols cause opportunities for disease spreading
What microorganisms are pathogenic?
Only a minority of microorganisms that associate with other organsims such as plants, animals and humans are pathogenic
What percentage of microorganisms are advantageous or harmless?
A majority
Are all viruses harmful to the organisms they’re attached to?
yes
What are some microorganisms capable of inhabiting?
Extreme environmental conditions that are unfavorable or even lethal for other organisms
What are the microorganisms capable of inhabiting extreme environmental conditions that are unfavorable or even lethal for other organisms?
Extremophiles
Where are extremophiles found?
inside the earth’s crust
deep sea at high pressures
extreme acidic/basic conditions
hydrothermal vents
frozen sea water
anaerobic conditions
How are extremophiles classified?
According to the conditions in which they grow in
What are the different types of extremophiles?
Thermophiles
Psychrophiles
Acidophiles
Alkaliphiles
Halophiles
Barophiles
What conditions are Thermophiles found?
High temperatures
What conditions are Psychrophiles found?
Low temperatures
What conditions are Acidophiles found?
Acid pH
What conditions are Alkaliphiles found?
Basic pH
What conditions are Barophiles found?
High pressure
What extreme environments consist of more than one extreme condition?
Many hot springs are acidic or alkaline in nature at the same time
Deep seas are cold and remain in high pressure
How do microorganisms live in environments consisting of more than one extreme condition?
They’re adapted to live with more than one extreme condition
Describe the rate of growth and reproduction of microorganisms
Its high
What do microorganisms possess due to their smaller size?
A high surface area/volume ratio
What does having a high surface area/volume ratio mean?
They have a large surface area available for exchange of materials from external environment
As a result, flowing rate of materials into the inside of cells and the exist of waste materials to the outside of the cells increases and results in high metabolic rate
What is the result of microorganisms possessing a high surface area/volume ratio?
Flowing rate of materials into the inside of the cells and the exit of waste materials to the outside of the cells increases and results in a high metabolic rate
Therefore, average generation time, or the time required to double the population of microorganisms is relatively less
Describe the forms of microorganisms
they possess diverse morphological forms
Describe the shapes of bacteria
they possess diversity in their shapes, basically 3 distinct shapes
rod shape/bacillus
spherical shape/coccus
monococcus, diplococcus, streptococcus, staphylococcus, tetrads and sarcinae
How are bacillus bacteria arranged?
they may be arranged in to either diplobacillus or streptobacillus
How are spiral bacteria arranged?
Into either vibrio or spirillum or spirochete
Describe the shapes of cyanobacteria
They exhibit a great variety of shapes and arrangements, unicellular to long multi-cellular filaments
How do multicellular cyanobacteria appear?
As either filamentous or non-filamentous
Filamentous appear as chains and non-filamentous appear as clusters or colonies forming spherical, cubical, square or irregular shape
What are the morphological varieties of viruses
There are 2 morphological varieties found in viruses based on their symmetry of protein coats; icosahedral and helical
Describe the shape of fungi
Some of them are unicellular and others multicellular, consisting of a mass of fine tubular branching threds known as hyphae, collectively forming mycelium
Hyphae might be septate or aseptate
What are prions?
They are smaller proteinaceous particles
Describe the morphology of unicellular protists
They possess a wide range of morphological diversity
Describe the nature of mollicutes
They are pleomorphic (variable shapes)
How are the nutritional types of microbes classified?
Based on the sources of carbon and energy
What are the 4 major nutritional types seen among microorganisms?
Chemoautotrophs
Chemoheterotrophs
Photoautotrophs
Photoheterotrophs
How are microorganisms classified into 4 physiological groups?
Based on the utilization of O2(g)
What are the 4 physiological groups of microorganisms?
Obligate aerobes
Obligate anaerobes
Facultative anaerobes
Microaerophiles
What physiological diversity do some microbes capable of fixing atmospheric molecular nitrogen show?
Free-living nitrogen fixing microbes
Symbiotic nitrogen fixing microbes
What are bacteria?
They are single-celled prokaryotic organisms
What is the morphological form of bacteria?
They show different morphological forms and arrangements
What is the most obvious structural feature of bacteria?
The shape of individual cells
What are the 3 basic shapes of bacteria?
- spherical; coccus
- rod shaped; bacillus
- spiral shape
What happens during the cell division of bacteria?
Cells can remain attached to each other and form different forms of cell arrangements
Write the form of cell arrangement of coccus bacteria
Cells divide in one plane.
Divided cells detach from each other after cell division
Write the form of cell arrangement of diplococcus bacteria
Cells divide in one plane.
Divided cells remain in pairs
Write the form of cell arrangement of streptococcus bacteria
Cells divide in one plane
Divided cells remain attached in chain like pattern
Write the form of cell arrangement of tetrad bacteria
Cells divide in two planes producing 4 cells remain attached together
Write the form of cell arrangement of sarcinae bacteria
Cells divide in 3 planes and remain attached in groups of 8 cells
Write the form of cell arrangement of staphylococcus bacteria
Cells divide in multiple planes and form grape like clusters of cells
How do bacilli divide?
Across their short axis. Therefore, there re a few cell arrangement forms
What is the cell arrangement of single bacillus bacteria?
Single rod
What is the cell arrangement of diplobacillus bacteria?
Remain in pairs after cell division
What is the cell arrangement of streptobacillus bacteria?
occur in chains after cell division
Describe the cell arrangement of spiral bacteria?
They have one or more twists, they are never straight
What is the form of cell arrangement of vibrio bacteria
Bacteria look like curved rods
What is the form of cell arrangement of spirillum bacteria
Helical shape, like a corkscrew and rigid body
What is the form of cell arrangement of spirochete bacteria
Helical shape, flexible body
What is the source of energy of photoautotrophs
Light
What is the source of energy of photoheterotrophs
Light
What is the source of energy of chemoautotrophs
inorganic chemicals
What is the source of energy of chemoheterotrophs
organic chemicals
What is the source of carbon of photoautotrophs
Carbon dioxide (inorganic carbon)
What is the source of carbon of photoheterotrophs
Organic carbon
What is the source of carbon of chemoautotrophs
Carbon dioxide (inorganic carbon)
What is the source of carbon of chemoheterotrophs
Organic carbon
Give examples for photoautotrophs
Purple sulfur
Green sulfur bacteria
Give examples for photoheterotrophs
Purple non sulfur bacteria
Give examples for chemoautotrophs
Nitrobacter
Nitrosomonas
Thiobacillus trioxidanes
Give examples for chemoheterotrophs
most bacteria
Describe obligate aerobic microorganisms tolerance to oxygen
These bacteria require oxygen for their survival. They generate energy by oxidative phosphorylation
Describe obligate anaerobic microorganisms tolerance to oxygen
They cannot survive in the presence of oxygen. These microorganisms generate energy by fermentation
Describe facultative anaerobic microorganisms tolerance to oxygen
These microorganisms prefer to grow in the presence of oxygen producing energy by oxidative phosphorylation, but they can also grow in anaerobic environments using fermentation
Describe microaerophilic microorganisms tolerance to oxygen
These microorganisms can grow only in oxygen concentrations lower than those in the air
Give examples for obligate aerobic microorganisms
Acetobacter sp
Give examples for obligate anaerobic microorganisms
clostridium sp.
Give examples for facultative anaerobic microorganisms
Escherichia coli
Give examples for microaerophilic microorganisms
Lactobacillus sp
What microorganisms show diversity in nitrogen fixation?
Free living nitrogen fixing bacteria (Azotobacter sp)
Symbiotic nitrogen fixing bacteria (Rhizobium sp. with legume root)
How do microorganisms reproduce?
Mostly bacteria undergo asexual reproduction by binary fission, and in some occasion, fragmentation or budding.
In rare occasions, bacteria of two strains share a portion of genetic material through the process of ‘conjugation’
What is the process of conjugation?
In rare occasions, bacteria of two strains share a portion of genetic material through the process of ‘conjugation’
How are cyanobacteria named?
They’re named for their characteristic blue-green (cyan) pigmentation
What kinds of shapes and cell arrangements do cyanobacteria exhibit?
They exhibit a great variety of shapes and cell arrangements, unicellular to colonial forms
Describe the unicellular form of cyanobacteria
Here, cells separate after cell division. However, in nature majority of unicellular forms stay together by copious secretion of mucilage by daughter cells.
In nature, how to majority of unicellular forms stay together?
by copious secretion of mucilage by daughter cells
Describe the colonial form of cyanobacteria
Cells remain attached by walls or held in a common gelatinous matrix forming a colony of cells.
Colonies may either be non-filamentous or filamentous.
Describe the non-filamentous colonial form
Depending on the plane of division and direction there are different arrangements such as spherical, cubical, square or irregular shape.
Filamentous colonial form is the result of cell division in a single plane and a single direction forming a chain or thread like structure
Describe the nutrition of cyanobacteria
They are photoautotrophs that carry out oxygenic photosynthesis similar to plants and algae
Write what organisms cyanobacteria are similar to in terms of nutrition
plants and algae
What are many cyanobacteria capable of?
Fixing atmospheric nitrogen
Give ex. for free living nitrogen fixing cyanobacteria
Nostoc sp.
Anabaena-azolla symbiotically fix nitrogen with its partner, Azolla sp. (water fern)
In most cases, where does nitrogen fixation take place?
In special cells called heterocyst
What enzyme is nitrogen fixation catalyzed by?
Nitrogenase in the heterocyst
Where is enzyme nitrogenase located?
In the heterocyst
What is nitrogenase sensitive to?
Oxygen
Why do heterocyst carry thick cell walls?
To protect nitrogenase from oxygen that could diffuse from neighboring photosynthetic cells and from air or water
Aside from heterocyst, what are the other specialized cell type cyanobacteria carry?
akinete
What are akinete?
They are thick walled resting spores with stored food
What are akinete resistant to?
drought and high temperature
As a result of akinete being resistant to drought and high temperature, what occurs?
Akinete is able to survive during unfavorable environmental conditions although vegetative cells dries out
How do cyanobacteria reproduce?
Only by asexual methods
What do single unicellular and colonial non-filamentous types undergo?
Simple cell division
How do colonial filamentous and colonial unicellular forms reproduce?
By fragmentation
Describe fungi
Fungi are eukaryotes. They may be unicellular (yeast) ot multicellular (molds)
Some multicellular fungi form mushrooms
What do molds form?
Visible masses called mycelia, which are composed of long filament like structures called hyphae
What do many molds contain?
Cross-walls called septa (singular, septum)
What do septa do?
Divide hyphae into distinct single nucleate cell-like units
What are coenocytic hyphae?
Some molds do not contain septa in their hyphae resulting in long continuous cells with many nuclei
Where are coenocytic hyphae found?
The cottony growths are sometimes found on bread and fruit are mycelia of molds
Describe the nutrition of fungi
They are chemoheterotrophs and acquire food by absorption
What is the main mode of nutrition of fungi?
Saprophytic mode of nutrition
What do fungi play an important role in?
In the food chain by decomposing dead plant materials by secreting enzymes and thereby recycling vital elements
What other modes of nutrition can be found in fungi?
Parasitic (plant and animal pathogens) and mutualistic (lichens and mycorrhizae) modes of nutrition
How do unicellular fungi reproduce?
By fission or budding
How do filamentous fungi (molds) reproduce?
Asexually and/or sexually by producing spores
Describe the shape of unicellular protists?
They are pleomorphic, vary in their shapes and possess locomotive structures such as pseudopods, cilia or flagella
What locomotive structures do unicellular protists possess?
locomotive structures such as pseudopods, cilia or flagella
How do unicellular protists exist?
either individually or form colonies. some join together and form filaments
What modes of nutrition are found among protists?
Photoautotrophic, heterotrophic, and mixotrophic modes of nutrition
What are the respiratory modes of protists?
Aerobic, anerobic, facultative anerobic respiratory modes
How do some algae contribute to symbiotic interactions?
With lichens
How do protists reproduce?
Sexually by gametes and asexually by fission
What are mollicutes?
They are prokaryotes included in domain bacteria.
Why are mycoplasma and phytoplasma considered unique?
Due to their absence of cell walls
Describe the shape of mycoplasma
They are pleomorphic, vary in shape from spherical to filamentous
What is the smallest prokaryotic group of organisms invisible under light microscope?
Mycoplasma
What don’t mycoplasma contain?
Flagella
What are almost all mycoplasma parasites of?
Humans and animals
What in high amounts do mycoplasma require?
Organic Growth Factors
How do mycoplasma reproduce?
By budding and binary fission and do not produce spores
What are the respiratory modes of mycoplasma
Aerobic or facultative anerobic
How do phytoplasma resemble mycoplasma?
They are similar in size
Both can only be seen under an electron microscope
Shape varies from spherical to filamentous
Describe the nature of phytoplasma
They only infect plants and are generally present in phloem sap.
They cannot grow in artificial media
How are phytoplasma mostly transmitted?
By leafhoppers
Where do phytoplasma reproduce?
In both leafhoppers as well as plant body
How do phytoplasma reproduce?
By budding and binary fission
What are the modes of respiration of phytoplasma?
Aerobic of facultative anaerobic
What are the characteristic features of viruses
They are neither prokaryotes nor eukaryotes and do not show any cellular organization
They do not possess any metabolic activity or reproduction when they are out of living host cells. Thus, they are not considered as living organisms.
However, once they get into the host cells, they multiply and cause infection through various metabolic pathways, shows characteristics of living organisms. Since they can only multiply within living host cells, they are called obligate parasites.
They are very small and can only be seen through an electron microscope
They possess simple structures, usually composed of a central core of a nucleic acid and surrounded by a protein coat called the capsids made up of a fixed number of protein subunits called capsomeres.
Viruses may have either DNA or RNA as their genetic material.
They do not have protein synthesis machinery such as additional RNAs or enzymes for protein synthesis. Therefore, they depend on host cell’s protein synthesis machinery.
RNA viruses consist of reverse transcriptase enzymes for reverse transcribing RNA into DNA
Why are viruses not considered living organisms?
Because they do not possess any metabolic activity or reproduction when they are out of living host cells
Why are viruses called obligate parasites?
Since they can only multiply within living host cells, they are called obligate parasites.
Describe the structure of viruses
They possess simple structures, usually composed of a central core of a nucleic acid and surrounded by a protein coat called the capsids made up of a fixed number of protein subunits called capsomeres.
On what basis can two basic morphological symmetries be identified?
On the basis of capsid architecture
What are the 4 types of morphological forms?
helical
polyhedron
complex
enveloped
What are helical viruses?
They are long rigid or flexible rods
Give ex. for helical viruses
Rabies virus
What kind of symmetry do icosahedron/polyhedral viruses show?
Icosahedron symmetry
What kind of symmetry do complex viruses show?
They exhibit more than one form of symmetry with additional structures
Give ex. for icosahedron/polyhedral viruses
Adeno virus
Give ex. for complex viruses
bacteriophage
What kind of symmetry do enveloped viruses show?
Roughly spherical, capsid covered by envelopes
Give ex for enveloped viruses
Herpes simplex virus
What is the multiplication of viruses?
A single virus can give rise to thousands of similar viruses in a single host cell.
What is the result of virus multiplication?
Therefore, viruses cause serious damages to their host leading to severe diseases in plants, animals and bacteria.
What are bacteriophages capable of?
They’re a typical group of viruses capable of infecting bacteria
How do bacteriophages multiply?
Lytic cycle or lysogenic cycle
What is difference between the lytic cycle and lysogenic cycle?
It involves with the lysis of the host cells whereas the lysogenic cycle allows viral DNA incorporating into host DNA and multiply without causing lysis of the host cell
What are the 5 distinct steps of the lytic cycle?
Attachment
Penetration
Biosynthesis
Maturation
Release
Describe the attachment step of the lytic cycle
The first step is the attachment of virus to a matching receptor site on the bacterial cell
Describe the penetration step of the lytic cycle
After attachment, bacteriophage injects its DNA into the bacterial cell. This is facilitated by an enzyme which breaks down the bacterial cell wall
Describe the biosynthesis step of the lytic cycle
The next step is biosynthesis of viral DNA and proteins in the host cytoplasm using host resources. This stage induces degradation of host cell DNA
Describe the maturation & assembly step of the lytic cycle
Once bacteriophage DNA and proteins and synthesized, DNA and capsid are assembled to form complete virus particles. This is called maturation
Describe the release step of the lytic cycle
Finally, bacteriophage induce bacterial cell to break open (lyse). Newly produced bacteriophages are released from the host cell. These released bacteriophages can start another lytic cycle in cells in the vicinity
What do viroids consist of?
They consist only of short piece of naked RNA with no protective layer such as protein coat
How can viroids multiply?
They can only multiply within a living host cell using host cell resources. However, viroids do not contain any gene and only carry signals for their multiplication
What do viroids infect?
Plants, but no other life forms till to date
What are prions?
They are proteinaceous infectious particles. Their size is smaller than virus.
How do prions replicate?
Although prions lack nucleic acid they can replicate with the help of a host’s gene that encodes the prion protein
What is the size of prions
Their size is smaller than virus
Where are prions found?
in disease causing agents in some birds and mammals.
What kind of diseases are caused by prions?
Neurological diseases
Give ex. for the neurological diseases caused by prions
Transmissible Spongiform Encephalopathies (TSEs)
Mad cow disease
Creutzfeldt-Jacob Disease (CJD)
Describe Transmissible Spongiform Encephalopathies (TSEs)
Large vaculoes develop in the brain giving a sponge-like appearance
When did mad cow disease emerge in cattle?
In 1987
What is a human disease caused by prions?
Creutzfeldt-Jacob Disease (CJD)
Why is it essential to culture microorganisms on artificial media?
For the study of morphology and biochemical properties of microorganisms
What are the basic laboratory techniques to be followed in culturing of the microorganism of interest without any contamination?
Preparation of artificial culture media
Sterilization techniques
What is sterilization?
It is the process of removal or destruction of all forms of microbial life, including endosperms
What are the 2 types of sterilization?
Physical sterilization
Chemical sterilization
What are some physical methods used in sterilization?
Sterilization by moist heat, dry heat, filtering using membrane filters, exposure to UV radiation
What is moist heat sterilization?
Here, moist heat is used to destroy the microorganisms present in the desired materials such as culture media, temperature labile reagents/fluids and various laboratory utensils
How is moist heat sterilization done?
By denaturing proteins by high temperature and pressure
Give an example for denaturing proteins by high temperature and pressure?
Autoclaving
Pressure cookers can also be used
Explain autoclaving
In an autoclave, steam with 121c temperature at pressure of 1atm/ 15 psi is used for sterilization.
Extending the above condition for 15 minutes is sufficient to kill all microorganisms (except prions) and their endospores.
What condition is sufficient enough to kill all microorganisms and their endospores?
Extending the above condition for 15 minutes is sufficient to kill all microorganisms (except prions) and their endospores.
What is autoclaving used for?
sterilizing culture media, solutions, syringes and needles, healthcare instruments and various other items that can withstand high temperatures and pressure.
Glassware can also be sterilizaed with an autoclave if care is taken to ensure that the steam contacts all surfaces
What is dry heat sterilization?
Here, dry heat is used to destroy the microorganisms present in the desired materials such as glasswares, petridishes, pipettes, inoculation loops, inoculation needles, scalpels, etc
What is direct flaming?
It is a simple method of dry heat sterilization used in laboratories to sterilize inoculating loops, inoculating needles and scalpel blades by heating them on the flames of bunsen burners/ hot spirit lamps until they reach red hot
What is incineration?
It is mostly done in an incinerating oven. It is used to sterilize hospital waste. Microorganisms are burned to ash during direct flaming and incineration
Where is incineration mostly done?
In incinerating ovens
What is hot-air oxidization?
Microorganisms are killed by oxidization. Items to be sterilized are heated to about 170c and maintain for 2 hrs in a dry air oven.
Where is hot-air sterilization used?
To sterilize glassware such as petri dishes, flasks, beakers bottles and glass pipettes
What is pasteurization?
Louis Pasteur found spoilage of beer and wine can be prevented by applying mild heat that kills organisms causing spoilage without seriously damaging the taste, texture, and nutritional content of the product.
Later, the same principle was applied to milk products, now known as pasteurized milk
What are the objectives of pasteurization?
Eliminating pathogenic microorganisms and reduce microbial number which prolongs milk quality under refrigeration
What is High temperature short-time pasteurization (HTST)
It uses temperature of at least 72c for 15 seconds
What is Low Temperature Long Time (LTLT) pasteurization?
It uses temperature of at least 63c for 30 minutes
What are the 2 main methods of pasteurization
HTST
LTLT
Name another method milk can be sterilized by?
Ultra high temperature (UHT) pasteurization. Here, milk is heated to about 140c in less than 5 seconds by flashing steam and this milk can be stored for several months without refrigeration
What is boiling?
Boiling the materials such as surgical instruments to 100c. Most pathogenic microorganisms are killed at boiling temperature
What is filtration used for?
It is used to sterilized heat sensitive liquids such as solutions containing enzymes, vitamins, antibiotics, vaccines and some culture media
How is filteration done?
Material to be sterilized is passed through a filter by using vacuum. Filter retains microorganisms and the liquid is passed through the filter.
Give ex for filtration and the reasons they are used?
Membrane filters are widely used to sterilize heat sensitive solutions.
Pores of membrane filters are from 0.01 um to 0.45 um size, retain almost all the microorganisms including viruses and some large protein molecules
Give ex for filtration and the reasons they are used?
Membrane filters are widely used to sterilize heat sensitive solutions.
Pores of membrane filters are from 0.01 um to 0.45 um size, retain almost all the microorganisms including viruses and some large protein molecules
What does UV radiation do?
It kills microorganisms that faills into direct exposure, either through destruction or damaging DNA
What is a major disadvantage of UV?
Radiation doesn’t penetrate through solid surfaces and coverings such as paper, glass and textile, so anything to be sterilized should have direct contact with radiation
Where is UV radiation commonly used?
It is commonly used to sterilize air in hospital rooms such as operating theatres and nurseries
What are the chemical methods are currently used in sterilization?
A few chemicals such as ethylene oxide and chlorine dioxide (both are gases) are currently used as chemical sterilizing agents
How do the majority of chemical agents sterilize?
By reducing microbial populations to safe levels or removing vegetative forms of pathogens
What is the function of ethylene?
Ethylene oxice kills microorganisms and endospores.
Where is ethylene oxide used?
It is highly penetrative. Therefore ethylene oxide is used to sterilize mattresses in hospitals.
What is chlroine dioxide used for?
It has been used to fumigate enclosed building areas contaminated with endospores of Bacillus anthracis
Where is chlorine dioxide used?
It is most commonly used in water treatment prior to chlorination
How are microorganisms studied?
Since they cannot be studied in their natural habitat such as soil, water or air, we need to bring them to the laboratory and provide similar conditions for their growth and reproduction
What is a culture medium?
A nutrient material prepared for providing nutrition and anchorage essential to the growth of microorganisms at the laboratory condition is called a culture medium
What are non-culturable microorganisms?
Some microorganisms cannot be grown on a laboratory culture media, They are non-culturable microorganisms
What kind of medium is required for microorganism growth?
Some microorganisms grow well on any culture medium whereas other microorganisms require a special medium
What should the culture of microorganisms present in a certain soil sample contain?
Necessary nutrients, sufficient moisture and suitable pH
What should the medium initially be?
Sterile; it should not contain any living microrganisms
How should the culture media initially be sterile?
When preparing a culture medium, all glassware and liquid nutrient solutions should be sterilized
What are the 2 general media commonly used to grow bacteria and fungi respectively
Nutrient agar (NA)
Potato dextrose agar (PDA)
What is nutrient agar made up of?
Peptone
Meat extract
Sodium chloride
Agar
Distilled water
What is PDA made up of?
Potato
Glucose
Agar
Distilled water
What is used as a solidifying agent in culture mediums?
Agar
What does agar solidify?
Temperatures below 40C, which means a culture medium containing agar is a solid medium
For growing microorganisms, where is solid culture medium usually contained in?
Petri dishes
Test tubes
Why do we have to prepare microrganisms for observation?
Because most microorganisms appear almost colorless when viewed through a standard light microscope
How are microrganisms prepared?
By staining (coloring the microorganisms with a dye)
What must be done before microorganisms stain?
They must be fixed (attached) to the microscope slide
What is a simple stain?
An aqueous or alcohol solution of a single basic dye
What is the primary purpose of a simple stain?
To highlight the entire microorganism so that cellular shapes, cell arrangements, and basic structures are visible
What are some simple stains commonly used in laboratories?
Methylene blue
Crystal violet
Safranin
How are microorganisms in humans during birth like?
Generally, humans are free of microorganisms at birth
Where do newborns get in contact with microorganisms first?
At the vagina of the mother
What are the bacteria newborns get in contact with at first?
Lactobacilli (they colonize the intestine of the newborn)
After birth where does microbial populations begin to establish?
The inside or on the body surface. These are called normal microbiota of the human body
What part of a healthy human body are free from microorganisms?
Internal tissues of a healthy human body
Where does a part of microorganisms colonize?
On skin
Where does majority of microorganisms colonize?
On inner surfaces such as mucous membranes of nose, throat, upper respiratory tract, intestinal tract and genitourinary tract
How many microrganisms does a healthy human have?
A large no. of microorganisms
It has been estimated that the human body consists of 1 x 1014 microbial cells for 1 x 1013 total body cells, which means a 10 times more microbial cells than human cells
How are the majority of microorganisms like in the body?
They are generally harmless or even beneficial
Give an ex for an organisms beneficial to the body
Minimal colonization of Escherichia coli at large intestine prevent colonization of pathogenic bacteria such as salmonella typhi E coli
at large intestine prevent the colonization of pathogenic bacteria such as Salmonella typhi E coli. in large intestine synthesizes vitamin K and some B vitamins that are absorbed into the bloodstream and used by body cells
What has led to the study of probiotics?
Recent interest in the important of bacteria to human health
What are probiotics?
Live microbial cultures
Give ex. for probitoics
Yoghurt exerts a beneficial effect
What has studies shown about the ingestion of certain lactic acid bacteria?
It can alleviate diarrhea and prevent colonization of Salmonella enterica during antibiotic therapy
What are opportunistic pathogens?
Although majority of human microbiota are harmless, some of them may change their interactions with the human body under certain conditions and cause infections. Those microorganisms are called opportunistic pathogens
Give an ex. for opportunistic pathogens
E.coli is generally harmless as long as it remains in the large intestine. However they may cause diseases if they enter other body parts (urinary bladder- urinary tract infection, lungs- pulmonary infection)
What is a pathogen?
An orgnaism or entity (non living entities such as virus and prions) capable of causing disease
What is a host?
An organisms within which the infected pathogens live on or in and multiply
What is pathogenicity?
The ability of a pathogen to cause disease in the host by overcoming the host’s defense
What is a parasite?
An organism or entity living on or in another living organism (host) and obtain nutrients and other resources from the host
What are the characteristics of pathogenic microorganisms?
Having optimal growth conditions (ex: temperature) that corresponds to the body conditions of the host
Having a structure to adhere to the host cells and protect against the host’s defense mechanisms (ex: capsule, pilli)
Produce toxins; endotoxins or exotoxins
Having enzymes for invasiveness such as phospholipase, lesithinase and hyaluronidase
Having enzymes such as DNase to alter the host’s metabolic processes
How do microbes express their pathogenicity?
By means of their virulence
What is virulence?
It is the degree of pathogenicity of the pathogen
How the virulence of pathogens vary?
Some pathogens are highly virulent (chicken pox virus) whereas some are less virulent/ non virulent
What are virulence factors?
A few genes of pathogenic microorganisms express factors which provide them the ability to infect their host and cause disease. such factors are called virulence factors
Describe the relationship between a host and a pathogen
It is dynamic, each modifies the activities and functions of the other
What is the result of the host and a pathogen having a dynamic relationship?
As a result, the outcome of such a relationship depends on the virulence of the pathogen and the effectiveness of the host defense mechanism
What do virulence factors enhance?
The pathogenicity and allows pathogens to invade and colonize hose tissues and disrupt normal body function
What are the 2 major mechanisms pathogens use for pathogenicity
Invasiveness
Toxigenicity
What is invasiveness?
It is the ability of pathogens to invade tissues by overcoming the host’s defense mechanisms and multiply for colonizing
What are the extracellular enzymes produced by pathogens contributing to their invasiveness?
Phospholipase - Destroy animal cell membranes
Lesithinase - Hydrolyzes the lecithin component of the lipid in the cell membrane
Hyaluronidase - Destroys the body tissue by breaking down the hyaluronic cid which is a cementing substance between cells
Write the functions of phospholipase
Destroy animal cell membranes
Write the functions of Lesithinase
Hydrolyzes the lecithin component of the lipid in the cell membrane
Write the functions of Hyaluronidase
Destroys the body tissue by breaking down the hyaluronic cid which is a cementing substance between cells
How do pathogenic microorganisms enter passively?
Through various portals or natural openings such as wounds on the skin, respiratory, gastrointestinal and genito-urinary tracts
What is toxigenicity?
The ability of microorganisms to produce biochemical substances known as toxins that disrupt the normal functions of cells These proteins or lipopolysaccharides produce specific harmful effects on the hose, and thus are called biological poisons
Why are toxigenic microorganisms referred to as biological poisons?
These proteins or lipopolysaccharides produce specific harmful effects on the hose, and thus are called biological poisons
Give ex. for toxigenic microorganisms
Endotoxins
Exotoxins
Write the features of endotoxins
They are lipopolysaccharides
These are thermos-stable toxins which are part of the microbial cell.
Toxins are released when the bacteria die and the cell wall breaks apart
All endotoxins cause the same signs of symptoms regardless of the species of pathogen.
These symptoms include chills, fever, weakness, generalized by ached and sometimes shock and death
Endotoxins are produced only by gram-negative bacteria
Give ex. for endotoxins
Lipopolysaccharides of the cell walls of salmonella typhi
Write the features of exotoxins
Exotoxins are produced inside bacterial cells as part of their growth and metabolism are are secreted or released to the surrounding environment after cell lysis.
Exotoxins are proteins. Majority of them are enzymes.
Dye to their catalytic nature even a small amount of toxin is quite harmful.
These are thermo-labile protein toxins, being inactivated by boiling.
Exotoxins are most commonly produced by gram-positive bacteria and a few gram-negative bacteria
What are the 3 types of exotoxins
Neurotoxins
Enterotoxins
Cytotoxins
Write the features of neurotoxins
Interfere with normal transmission of nerve impulses
Give ex. for neurotoxins
Toxins produced by Clostridium tetani
Write the features of enterotoxins
Stimulates the cells of gastrointestinal tract in an abnormal way
Give ex. for enterotoxins
Toxins produced by Vibrio cholera
Write the features of cytotoxins
Kills host cells by enzymatic attack
Give ex. for cytotoxins
Toxins produced by corynebacterium diptheriae
What does microbial disease start with?
From the avoidance and prevention of opportunities of getting infection to treatment or curative methods after infection
What is the best method to avoid infectious diseases?
Good hygienic practices in day to day life
What plays an important role in the prevention of infections?
Antiseptics, disinfectants and immunization
What are antiseptics and disinfectants?
The chemical substances that are used to kill or reduce microbial population in order to prevent infection
What microorganisms are antiseptics and disinfectants not effective against?
some microorganisms like polio virus, tuberculosis bacterium, spores of bacteria and fungi are not destroyed by most antiseptics and disinfectants
What is the major difference between antiseptics and disinfectants?
Antiseptics can be safely and directly applied to the human body, whereas disinfectants cannots.
Therefore, antiseptics are used in disinfection of living surfaces like skin. Disinfectants are used in disinfecting non-living surfaces such as operation theatres, bathing areas, sinks, kitchen tops, cutlery, drains, etc
Where are antiseptics used?
antiseptics are used in disinfection of living surfaces like skin
Where are disinfectants used?
disinfecting non-living surfaces such as operation theatres, bathing areas, sinks, kitchen tops, cutlery, drains, etc
How are antiseptics and disinfectants generally formulated?
As liquids
How does the effectiveness of antiseptics and disinfectants vary?
with concentration, duration of exposure, temperature and presence of organic matter
Give ex. for antiseptics
ethanol
isopropanol
chloroxylenol
Give ex. for disinfectants
phenol
hypochlorites (calcium hypochlorite and sodium hypochlorite)
When the body’s defense fails to protect the body from the infection or overcome the disease, how is it treated?
Chemotherapy with antimicrobial drugs
What do antimicrobial drugs do?
They kill or interfere with the growth of microorganisms without damaging the host
What are antibiotics effective against?
They are effective antimicrobial drugs against bacteria
What are broad spectrum antibiotics?
Some antibiotics affect against a broad range of bacteria and they are termed as broad-spectrum antibiotics
What are narrow-spectrum antibiotics?
Other antibiotics affect only against a specific group of bacteria and they are narrow-spectrum antibiotics
What are the various modes of action antibiotics show?
Inhibition of cell wall synthesis - Penicillin
Inhibition of protein synthesis - Erythromycin, Tetracycline
Disrupting plasma membrane - Daptomycin
Inhibition of RNA/DNA synthesis - Rifampin
What antibiotic helps in the inhibition of cell wall synthesis?
Penicillin
What antibiotic helps in the inhibition of protein synthesis
Erythromycin, Tetracycline
What antibiotic helps in the Disrupting of plasma membrane
Daptomycin
What antibiotic helps in the Inhibition of RNA/DNA synthesis
Rifampin
What is a vaccine?
A suspension of weakened pathogens or fractions of organisms that is used to induce immunity is a vaccine
What are vaccines used to control?
They are frequently used to control diseases caused by viruses because there is no other control methods once infected
What are the different types of vaccines?
Live attenuated vaccines
Inactivated vaccines
Subunit vaccines
What are live attenuated vaccines?
Vaccines which contain live pathogens which were deliberately weakened for its pathogenicity
What do live attenuated vaccines mimic?
An actual infection
Why do live attenuated vaccines provide lifelong immunity?
Since the pathogen is active inside the host, such vaccines provide lifelong immunity.
Is a booster required for live attenuated vaccines?
no
Give ex. for live attenuated vaccines
Measles, mumps and rubella (MMR)
Chickenpox
What are inactivated vaccines?
Pathogenic microorganism is inactivated or killed in the vaccine
What do inactivated vaccines require compared to live attenuated viruses?
Repeated booster doses
What do inactivated vaccines require compared to live attenuated viruses?
Repeated booster doses
What diseases are inactivated vaccines used for?
Virus diseases such as rabies, influenza, polio
bacterial diseases like cholera
What are subunit vaccines?
Subunit vaccines contain only the antigenic fragments of a pathogen that can induce immunity in the recipient
What is the best ex. for a subunit vaccine that have been used for a long time?
Toxoid vaccines
What do toxoids contain
They contain inactivated toxins derived from a pathogen
Give ex. for toxoid vaccines
Vaccines for tetanus, diphteria, etc
How are subunit vaccines produced presently?
using genetic engineering
Give ex. for subunit vaccines produced using genetic enginnering
Hepatitis B vaccines
What do subunit vaccines require to obtain full immunity?
repeated booster dose
How have microorganisms been exploited long before their discovery?
Babylonian and Sumerian civilizations used yeast to make alcohol as early as in 6000 BC
How were microorganisms used after their discovery?
Pure cultures of microorganisms are being used in food production
What did pure cultures of microorganisms being used in food production help?
This increases the understanding of microorganisms, their processes and their products.
At present, what are various industries based on?
Selected microorganisms and their qualities are in operation
Write the advantages of using microbial processes over chemical processes
simple nutritional requirements are sufficient for their growth
They are able to convert (metabolize) a wide range of raw materials
They are able to convert cheap raw materials into industrially important products
Due to higher gowth rate, they can convert the raw materials into products within a short period of time
Their growth conditions can be controlled to obtain desired end products
How can reactions be carried out?
at low temperatures, energy and pressures compared to conventional industrial methods
Describe the yield received from reactions compared to conventional industrial methods
They give higher yield with higher specificity
What can microbes obtain after being amendable to genetic manipulation?
desired yield and quality with high efficiency
What are the basic principles of metabolic processes of microorganisms for product formations?
- microbial cells are used as the end products ex: single cell proteins
- Microbial metabolic products are used as end products - they may be either primary end products or secondary metabolites ex: primary end products - alcoholic beverages, secondary metabolites - antibiotics
- Microbial metabolic processes are used as end products ex: bioremediation (heavy metal remediation), metal extraction (Cu,Fe) retting (production of fibers)
- Genetically modified microorganisms are used to produce end products
ex: productions of commercial enzymes (amylase from Aspergillus niger) vaccines (hepatitis B), hormones (insulin)
What is industrial microbiology?
It is the large scale production of economically important products using microorganisms and their metabolic processes
What expanded the scope of industrial microbiology?
recent technological and biotechnological advances expanded the scope of industrial microbiology
What is used in industrial microbiology?
Bacteria, fungi, algae and viruses
What are microorganisms considered as in industrial microbiology?
Miniature chemical factories
Why are microorganisms called miniature chemical factories?
Various energy releasing (catabolic) and energy acquiring (anabolic) chemical reactions take place here
What occurs within these miniature chemical factories?
Raw materials (substrates) are concerted into end products, one or more byproducts, and wastes.
End products can be separated from by purification to obtain a purified industrial products
How can end products be separated in industrial microbiology?
End products can be separated from by purification to obtain a purified industrial products
What are single cell proteins?
Microbial cells are grown in large scale as food supplement and rich in proteins are called single cell proteins
chemical reacto
Give ex. for the alcoholic beverages microorganisms are involved in the production of?
Beer
Wine
Sake
Toddy
Ethanol
What ferments sugars into ethanol and CO2?
Yeast, Saccharomyces cerevisiae
How much ethanol is produced globally by fermentation?
More than 70%
What is the most widely used fermentation substrate?
Sucrose derived from sugarcane
In addition to sucrose derived from sugarcane, what else is used as a fermentation substrate?
Simple sugars derived from plants and dairy waste are also used
Give ex. for alcoholic beverages and the way they are derived
Beer - by the fermentation of cereal grain salt
Wine - produced by the fermentation of grapes or other suitable fruits
Toddy - Produced by the fermentation of sap of palms such as Palmyra and coconut
Arrack - Produced by the fermentation of palm tree sap such as coconut and sugarcane
What are the 2 steps in vinegar production?
Alcoholic fermentation: sugars in malted grain, sap of palms, sugarcane and fruit juices is fermented by S. cerevisiae. Ethanol is subjected to acetic acid fermentation.
Acetic Acid fermentation: Ethanol derived from alcoholic fermentation undergoes incomplete oxidation and is concerted to acetic acid. This process is highly aerobic and involves Acetobacter sp. and Gluconobacter sp
Write the chemical equation for the production of vinegar.
C2H5OH ——————————–> CH3COOH + H20
Acetic acid bacteria
How are dairy products made?
By the fermentation of milk
How is sugar lactose in milk fermented?
Sugar lactose in milk is fermented by lactic acid producing bacteria into lactic acid. These bacteria are killed during pasteurization. So they are added externally when making dairy products.
Why are bacteria added externally when fermenting sugar lactose in milk?
These bacteria are killed during pasteurization. So they are added externally when making dairy products.
Give examples for dairy products produced by fermentation
Curd and yoghurt is produced by the fermentation of lactose sugar in milk by a mix population of Lactobacillus bulgarcius, Lactococcus lactis and S. thermophilus. L. bulgaricus adds flavor and Streptococcus spp. adds a creamy texture and flavor
Production of cheese - Streptococcus sp. Penicillium molds
Lactic acid is commercially produced by using waste products from cheese and butter industry. L bulgaricus ferments lactose into lactic acid.
How is a majority of commercially produced organic acids obtained?
Through microbial fermentation
What fermentation substrates have been used to produce organic acids?
Beat or Cane molasses
What organisms have been used to produce organic acids?
Aspergillus niger
Give ex. for organic acids
Citric acids - sucrose fermented by Aspergilus niger
What is leaching?
Some metals from ores are extracted with the help of microorganisms. This process is called leaching.
What is one of the best ex. for extraction?
Extracting copper from lower grades of copper ore which other extraction methods are unprofitable. Thiobacillus ferroxidans recover copper from the ore that contains iron and sulphur. 70% of copper in the ore can be recovered by this microbial process.
What other metals aside from cu can be extracted using microbial processes?
Uranium, gold and cobalt ore
What microorganism produces riboflavin vitamin?
Fermentation by fungi
What microorganism produces vitamin B12?
Pseudomonas sp. and Propionibacterium sp
What microorganism produces Vitamin C?
Acetobacter sp
What is the commercial production of vaccines done by?
A variety of microbial antigens used in active immunization against various diseases. Some of them are genetically engineered vaccines
Give an ex for genetically engineered vaccines used in active immunization
Hepatitis B vaccines
Give ex. for the commercial production of various antibody preparation used for passive immunization?
anti toxins against tetanus
Botulism toxin
Immunoglobulin against rabies
What are the enzymes commercially produced
Amylase: Aspergillus niger, A.oryaze, Bacillus subtilis
Protease: A. oryzae
Lipase: Rhizopus spp
Invertase: Sacchromyces cerevisiae
Cellulase: A.niger
What are the most important secondary metabolites of microorganisms?
Antibiotics
How are many antibiotics still produced by?
Microbial fermentation
Give ex. for antibiotics
Tetracycline: S. aureofaciens
Penicillin: Penicillium chrysogenum
Streptomycin: Streptomyces griseus
Conventionally, where is insulin extracted from?
animal pancreas
Why cant insulin often meet the demand?
Because this is expensive
How is insulin produced at the present cheaply?
By using genetically modified E.coli and S.cerevisiae
What is the insuline produced with genetic modifications similar to?
Human insulin
What are animal-derived hormones used as an alternative to earlier?
human growth hormones
How are animal derived hormones different from human growth hormones?
they work with less efficiency
How are human growth hormones produced successfully at present?
By genetically engineered E.coli in large scale
What is retting?
It is the process of loosening fibers from woody stem or other plant material such as coir
What is required for the plant materials in retting?
Plant materials must be immersed in water for varying periods of time depending on the plant material
What bacteria participates in retting?
Heterogenous bacterial populations participate in the process under aerobic or anaerobic conditions
How do bacteria participate in retting?
Bacteria secretes enzymes, mainly pectinases, to facilitate loosening
What are the main enzymes secreted by bacteria in retting?
pectinases
What is biogas?
Anerobic digestion of organic waste produces various gases called biogas
What is biogas?
Anerobic digestion of organic waste produces various gases called biogas
How does the type of biogas produced differ?
It depends on the substrate biodegraded
What are the products of biogas production
The activity of acetogenic bacteria on organic waste products produce carbon dioxide and hydrogen, whereas, the activity of methanogenic bacteria produces methane
Why is much attention given to renewable replacement fuels?
because petroleum-based fuel supply is expensive and sometimes uncertain.
What are some renewable replacement fuels?
Ethanol, Butanol, Biodiesel and biogas
In brazil, what is a large amount of ethanol produced by?
Microbial fermentation of sugarcane to be used as a source of fuel
How have ethanol and butanol been produced?
Efforts have been made to produce ethanol and butanol from cellulosic materials such as wood, wastepaper and cornstalks by using genetically modified bacteria
What have many researches go on to produce biodiesel from?
Microalgae
What is sugars in bread dough fermented by?
S. cerevisiae (baker’s yeast)
What is the primary function of fermentation in bread?
Generating carbon dioxide
How is bread dough produced?
With grain flour such as wheat, rye and rice.
What does dough do in the presence of CO2?
Dough traps CO2 and rises up due to the pressure during baking and forms an open crumb texture
How are various chemical substances not readily degradable in nature released?
Industries and agriculture
Give ex. for synthetic substances that are not biodegraded or very slowly degraded by microorganisms and retain in the soil for long periods and also contaminates groundwater?
Plastic
Residue of pesticides such as heavy metals
Insecticide DDT
Herbicide 2,4-D
What is bioremediation?
It is the technology that applies of living organisms to remove, degrade or detoxify pollutants
Where does bioremediation naturally occur?
In the soil
In what occasions can microorganisms be used in bioremediation processes?
In most occasions
What can the growth of microorganisms in polluted soils and water be stimulated to promote?
Biodegration/bio-removal of pollutants
What microorganisms can be used to degrade/remove a specific pollutant from polluted sites?
Microorganisms with selected properties or genetically modified microorgaisms with selected properties
What microorganisms can be used to degrade/remove a specific pollutant from polluted sites?
Microorganisms with selected properties or genetically modified microorgaisms with selected properties
What is bioremediation currently used for?
- remediate soil and water contaminated with oil spills, toxic metal waste, hazardous organic waste, etc
- decompose waste water from good processing and chemical plants
What does the accumulation of solid waste from house hold (garbage) possess?
Various environmental and health issues
In waste management, how is waste degraded by?
By microorganisms either aerobically or anaerobically
What does composting do?
It degrades waste anaeorbically
What happens at the end of composting?
Waste is converted to a stable material like humus
Where is most garbage placed?
As large compacted landfills or piles, where conditions are mostly anaerobic
In landfills or piles, how is waste degraded?
Anaerobically by using methanogenic bacteria
What is produced as a byproduct of the degradation process?
Methane gas
What can methane gas be used for?
Generate electricity or as natural gas
Why do microorganisms have various applications in agriculture?
For improving yield
Agronomic characteristics such as improved nitrogen and phosphorus absorption
Resistance to pest and diseases and tolerance to drought, etc.
What are the most limiting nutrients in soil for plant growth and development?
Nitrogen and phosphorus
Why are chemical fertilizers applied to the soil?
To improve bioavailability of nutrients such as nitrogen and phosphorus
What is done to improve bioavailability of nutrients such as nitrogen and phosphorus?
chemical fertilizers are applied to the soil
What can extensive use of synthetic fertilizer result in?
environmental problems such as deprivation of soil and water quality.
Why has much attention been given for microorganisms that can be applied into cropping systems?
To improve bioavailability of N and P
What are bio-fertilizers?
The microbial inoculants that may be applied into cropping systems to improve bioavailability of N and P
What is the most limiting nutrient among all major plant nutrients?
Phosphorous
Why can the bioavailability of phosphorous in any type of soil be neglected?
Because a very low amount of P applied to the soil remain available for plants
What bacteria contributes to improve the solubility of phosphorous in the soil solution?
Mycorrhizae and Phosphate solubilizing bacteria
How do Mycorrhizae and Phosphate solubilizing bacteria contribute to improve the solubility of phosphorous in the soil solution?
These bacteria and fungi secrete organic acids that dissolve minerals containing phosphorous and chelate cationic partners of phosphate ions, thereby release phosphorous into the soil solution
At present, where are commercial formulations of microbial bio-fertilizers available?
In the market
What is biological nitrogen fixation?
It is a process where microorganisms convert atmospheric molecular nitrogen into its soluble form
What happens to the soluble forms of nitrogen produced by nitrogen fixation?
By some plants directly or converted into desired forms of nitrogen (ex: symbiotic nitrogen fixing, free living nitrogen fixing)
Give ex. for symbiotic nitrogen fixing
Rhizobium sp. form intimate relationships with leguminous plants. The fixed nitrogen is released to the soil when plants die making nitrogen available for other plants. Various rhizobium inoculations are commercially available
Nitrogen-fixing cyanobacteria, Anabaena sp. form symbiotic associations with water fern Azolla. This system has been successfully used in rice cultivation in many countries
Give ex. for free living nitrogen fixing
Free living nitrogen fixing bacteria such as Azotobacter are present in high concentrations at rhizosphere
What are the plant growth-promoting substances produced by the many microorganisms in the plant rhizosphere?
Auxins (indole-3-acitic acid)
Cytokinins
What are the bacteria that produce plant growth-promoting substances in the plant rhizosphere?
Pseudomonas putida, P.florescens: auxin
Azotobacter sp. Rhizobium sp., subtilis, P. fluorescens, cytokinins
Acetobacter sp, Azospirillum sp: Gibberellin
What can the extensive use of chemical pesticides do?
It leads to hazardous side effects to people
These substances or their residues persist in food and the environment
The residual toxicity may affect non-target organisms
Overuse of pesticides develop resistance against pesticides among pests
What has been done to replace synthetic chemicals as pesticides?
Environmentally friendly and less toxic alternative strategies are required to replace them.
What are being explored to control pests and diseases?
Naturally occurring microorganisms
What are the microbial formulations currently commercially available and widely used in many cropping systems?
Entomopathogenic fungi
bacteria
viruses
What are entomopathogenic fungi?
These fungi infect a broad range of insects leading to insect death. They have been formulated into myco-insecticides
What are entomopathogenic bacteria?
Bacillus thuringiensis: insecticidal and toxic for many insect larvae: protein crystals produced by this bacterium are toxic to larvae when ingested. This toxin is called Bt toxin. After ingestion toxin is dissolved and lyse tissues of the guts of larvae. most biopesticide formulations currently in use are Bt-based.
How are most biopesticide formulations currently in use?
they are bt-based
What is bt toxin?
insecticidal and toxic for many insect larvae: protein crystals produced by this bacterium are toxic to larvae when ingested. This toxin is called Bt toxin.
What happens do bt toxin after ingestion?
After ingestion toxin is dissolved and lyse tissues of the guts of larvae.
What is composting?
It is a process used to convert plant remains into the equivalent of natural humus by microbial degradation. Degradation of organic matter by a mix population of microbes under warm, moist and aerobic conditions
How is degradation of organic matter done in composting?
Degradation of organic matter by a mix population of microbes under warm, moist and aerobic conditions
How does the initial activity of thermophilic bacteria on plant remains increase temperature of the pile to?
To 55-60c
What occurs as a result of the initial activity of thermophilic bacteria on plant remains increase temperature of the pile to 55-60c?
Thermophilic bacteria dominate in the degradation process for few days
What occurs in composting when the temperature decreases over time?
Thermophilic microbial population is replaced by mesophilic microbial populations
How can the process of thermophilic microbial population being replaced by mesophilic microbial population be enhanced?
By the addition of moisture and supply of oxygen through turning the pile.
What microbes can be used to contribute to the breakdown of organic matter into compost, under than bacteria?
fungi
Actinomycetes
protozoa
What does soil provide to the growth of microorganisms?
An adequate physical and chemical environment
What space and nutrients does soil include?
minerals
decomposing organic materials
water
gases such as carbon dioxide
oxygen
nitrogen
How does the soil environment change within a few cm dept of soil?
There are different amounts of oxygen, moisture, light and nutrition, increasing the diversity of soil microorganisms
Where can the largest community of bacteria be found in soil?
The top few cm of soil
What factor decreases along with increasing depth of soil?
Microbial number
What represents majority of soil microflora?
Bacteria
What can be found in the soil microflora, other than bacteria?
fungi
algae
protozoa
actinomycetes
Why are actinomycetes mentioned separately despite being a member of domain bacteria?
Because of their significances
What do microorganisms in soil play a major role in?
the decomposition of complex organic substances and participate in cycling of elements in biogeochemical cycles
Elements are oxidized and reduced by microorganisms for their metabolic requirements
Why are elements are oxidized and reduced by microorganisms?
for their metabolic requirements
What is mineralization?
It is the decomposition of plant and animal residue by using extracellular enzymes of bacteria and fungi.
What is the action of enzymes on mineralization?
They break down complex organic materials into simple inorganic materials such as CO2 and H20.
Why is mineralization a major process?
It is the way by which plant nutrients are made available and recycling
How does mineralization help?
- Helps remove plant and animal debris from the earth surface allowing other organisms to live
- Recycle minerals which are found in limited quantities on earth
Why do all organisms require nitrogen?
To synthesize proteins, nucleic acids and other nitrogen-containing compounds
What % of molecular N is available in the atmosphere?
About 80%
Why is it essential to convert atmospheric molecular N into bioavailable forms of N?
Because it is not biologically available for organisms
What bioavailable forms of N do certain groups of microorganisms fix gaseous molecular N into ?
ammonia
nitrate
nitrite
Why must nitrogen available on earth, organisms and atmosphere follow cyclic paths?
To fix gaseous molecular N into bioavilable forms of N
What are the 4 key steps in the nitrogen cycle?
Ammonification
Nitrification
Denitrification
Nitrogen Fixation
How does more than 90% of organic N in the soil exist?
As proteins
How are proteins from dead plants and animals decomposed?
By extracellular proteolytic enzymes secreted by microorganisms into amino acids
What is done to the resulting amino acids taken from the decomposed dead plants and animals?
They are take into microbial cells and are subjected to ammonification in which amino groups of amino acids are converted into ammonia (NH3)
How is ammonium ions (NH4+) ions produced in moist soil?
Ammonia is solubilized in water to produce NH4+
What is done by the ammonium ions produced by moist soil?
They are utilized by plants and soil microorganisms
What occurs to the ammonia in dry soil?
It rapids disappears into the atmosphere
What is nitrification?
It is the process of oxidation of nitrogen in the ammonium ion to produce nitrate
What is nitrification performed by?
By nitrifying bacteria living in soil
What are the 2 stages of nitrification?
- in the first stage, Microorganisms such as Nitrosomonas oxidizes ammonium ions into nitrites
- in the second stage, microorganisms such as Nitrobacter oxidizes nitrites into nitrates
How do plants utilize nitrate?
As their source of nitrogen. therefore, microorganisms play essential roles in providing nitrogen in bioavailable forms for plants and animals
What is denitrification?
In the absence of atmospheric oxygen, some microorganisms use nitrate and reduces it into n2. this process is called denitrification.
