Micro-organisms Flashcards
What did the invention of the microscope make possible?
The observation of very minute living organisms called micro-organisms.
What are micro-organisms commonly known as?
Germs or microbes.
Where are micro-organisms found?
Almost everywhere in nature: in air
What are pathogenic micro-organisms?
Disease-causing agents.
What type of micro-organism is mainly pathogenic?
Parasitic micro-organisms.
How do many micro-organisms benefit us?
Especially the saprophytic ones that bring about the decay of organic matter.
Name the types of micro-organisms.
Viruses
What is the cell structure of viruses?
No cell structure.
What is the cell structure of bacteria and blue-green algae?
Procaryotic cell structure.
What is the cell structure of protists, fungi and algae?
Eucaryotic cell structure.
Are most micro-organisms unicellular or multicellular?
Unicellular.
Give examples of multicellular micro-organisms.
Some fungi and algae.
What are the simplest and smallest micro-organisms?
Viruses.
Describe the cell structure of bacteria and blue-green algae.
Simple cell structure with the nucleus not enclosed within a membrane.
Describe the cell structure of protists, fungi and algae.
Complex cell structure with a nucleus confined within a membrane.
How do most micro-organisms survive unfavourable conditions?
By forming spores.
What is the technique of growing micro-organisms for study in the laboratory called?
Culture.
Which types of micro-organisms are easy to grow in culture media?
Bacteria
Can viruses be grown in culture medium like other micro-organisms?
No
What is the culture medium used for growing most micro-organisms composed of?
Agar
What is agar?
A jelly-like material obtained from seaweed.
At what temperature does agar liquefy and solidify?
Liquifies on heating and solidifies on cooling below 45 °C.
Will micro-organisms grow on agar alone?
No
Why is agar an ideal solid medium for culture?
Enzymes produced by the micro-organisms do not affect it.
What is nutrient broth?
A liquid culture medium containing beef extract and peptone without agar.
Do all micro-organisms have the same nutritional requirements?
No
What conditions do fungi grow well in?
Acidic pH (5-6) and a high sugar content.
Name an enriched medium used for culturing disease-causing micro-organisms.
Blood agar.
How are culture media usually stored?
In sterile petri dishes or test-tubes kept in a slanting position and covered.
What happens to micro-organisms on culture media when kept warm (25 to 37 °C)?
They grow and multiply rapidly to form colonies.
What is a colony?
A large number of micro-organisms of the same kind clumped together.
How is a colony formed?
By the growth and multiplication of a single micro-organism.
Can individual micro-organisms be seen with the naked eye?
No
What happens if there are too many micro-organisms in a sample on a petri dish?
The colonies will run into one another.
How can spaced-out colonies be obtained?
By diluting the sample.
What helps in the identification of micro-organisms?
The appearance of a colony.
What features of a colony should be noted?
Size
What is the appearance of mould colonies?
Large
How do yeast colonies compare to bacterial colonies?
Similar.
What are aseptic techniques?
Procedures that prevent microbial contaminants from the surroundings from entering a sample.
Name some aseptic techniques.
Sterilizing culture media and glassware
What is used to culture many protists and algae?
A medium of calcareous garden soil and water.
What is used for growing viruses?
Cultured bacteria
Where in the egg can the virus sample be inoculated?
The chorioallantoic membrane
How are cell cultures of animal and plant tissues grown?
As a single layer of cells on a solid surface or as a suspension in a fluid medium.
What are some components of a basic tissue culture medium?
Inorganic ions
What are the requirements for pH and osmotic pressures in a tissue culture medium?
They must be appropriate for the type of cell being cultured.
What is usually added to a chemically defined medium?
A little blood serum.
Where can cultures be started from?
Tissue fragments or a cell suspension.
At what temperatures are culture media incubated for cells from a mosquito and plant cells?
37°C for mosquito cells
How are most body cells grown in a culture similar to the original parent cells?
Structurally and functionally.
Give examples of functions that tissue cultures of cells can perform.
Muscle cells can contract
What are some uses of tissue culture in biological research?
Study of cell structure/metabolism
What are some applications of tissue culture?
Virus culture
What are the steps involved in the activity to show micro-organisms in our surroundings?
Prepare nutrient agar
How do we identify micro-organisms?
By observing their form and structure through a microscope
What type of microscope is used to study viruses?
Electron microscope (1000 000 x magnification).
What do simple stains like methylene blue and crystal violet show?
Size
What do differential stains show?
Structures like flagella
What is an example of a differential stain?
Gram’s stain.
What does Gram’s stain differentiate bacteria into?
Purple gram-positive and red gram-negative bacteria.
What is a common biochemical test for micro-organisms?
Fermentation of simple sugars to produce gas and acids.
Name examples of plant-like unicellular protists.
Diatoms
Name examples of animal-like protists.
Amoeba
Name common fungal micro-organisms.
Moulds and yeasts.
Name examples of algae.
Spirogyra and Volvox.
Do micro-organisms grow in air?
No
How are spores produced by micro-organisms dispersed?
By air movements.
What do spores do when they land on suitable substrates?
They germinate
What does nutrient agar exposed to air show?
The growth of various types of colonies of bacteria and fungi.
Name common micro-organisms found in the air.
Common cold virus
What are aerobes?
Micro-organisms that require oxygen.
What are obligate anaerobes?
Micro-organisms that can only grow and multiply in the absence of oxygen.
What are facultative anaerobes?
Micro-organisms that can grow in the presence or absence of oxygen.
Where can anaerobes form colonies?
Within the nutrient agar medium.
Are aquatic environments rich or poor in nutrients?
Rich in both organic and inorganic nutrients.
Name various aquatic environments that support a wide variety of micro-organisms.
Wells
What are the micro-organisms in aquatic environments commonly known as?
Plankton.
What proportion of the total biomass of aquatic environments do plankton make up?
A large proportion.
What are the groups of micro-organisms found in water?
Natural water micro-organisms
Where do natural water micro-organisms flourish?
In waters free from gross pollution.
Name examples of bacteria found in natural water.
Aquatic species of Coccus
Are most of these bacteria heterotrophic or autotrophic?
Most are heterotrophic
Name examples of blue-green algae found in natural water.
Oscillatoria
Name examples of protists found in natural water.
Autotrophic diatoms
Name examples of algae found in natural water.
Green algae
What is the role of algae and autotrophic protists in aquatic environments?
They are the main primary producers.
How are aquatic fungi related to moulds and mildews?
They are primitive and belong to the same class.
What happens to most soil and sewage micro-organisms that enter water bodies?
They die off eventually as they cannot reproduce successfully there.
Name examples of soil micro-organisms.
Nitrifying and nitrogen-fixing bacteria
Name examples of sewage micro-organisms.
Coliform micro-organisms (found in intestines of vertebrates) and decomposers of organic matter of plant and animal origin.
Name examples of coliform micro-organisms.
Viruses (enteroviruses and adenoviruses)
When do micro-organisms start to colonize the human body?
A few hours after birth.
What is the normal microflora of the human body?
The numerous bacteria
What are the important roles of the normal microflora?
Preventing invasion by pathogens by occupying surfaces and producing substances that interfere with pathogen survival/multiplication.
When do normal microflora become pathogenic?
When the host’s resistance becomes low.
Give an example of a normal microflora becoming pathogenic.
Spirilliae in the mouth causing throat infection in women with anaemia.
When do non-pathogenic micro-organisms in one part of the body become pathogenic?
When they move to a different environment in the body.
Give an example of a non-pathogenic micro-organism becoming pathogenic when it moves to a different environment.
E. coli in the colon causing urinary tract infections.
When do pathogenic micro-organisms usually establish themselves and cause diseases?
When body resistance is low
Name conditions that lower the body’s ability to resist pathogens.
Malnutrition
Name ways pathogenic micro-organisms enter the body.
Through cuts/wounds/abrasions (e.g.
How do pathogens harm the body?
By using the host’s nutrients and starving tissues
What determines the type of micro-organisms that grow and multiply in food?
Nutrient content
How does food become readily contaminated?
By animals (flies
What conditions promote rapid multiplication of micro-organisms in contaminated food?
Temperatures between 20-35°C and food not cooked enough to kill micro-organisms/spores/toxins.
What is a common illness associated with eating contaminated food?
Food poisoning.
Name common pathogenic micro-organisms that contaminate food.
Shigella sp.
Name diseases caused by these food pathogens.
Bacterial dysentery
Paralytic shellfish poisoning
Contaminated shellfish.
What are the non-living agents that carry micro-organisms?
Air
What are the living agents that carry pathogenic micro-organisms called?
Vectors.
Name important vectors.
Insects (houseflies
What are the two methods by which animal vectors carry micro-organisms?
Mechanical and biological.
Describe the mechanical method of transfer.
Animal vectors carry pathogens on their bodies; the pathogens do not grow or multiply on the vector.
Where do animal vectors that carry pathogens mechanically usually breed and live?
In filthy places like rubbish heaps
How do these vectors contaminate our food?
By feeding on it.
Why is the housefly an ideal mechanical vector?
It has a hairy sticky body and filthy habits.
Name pathogens carried mechanically by houseflies.
Shigella sp.
Describe the biological method of transfer.
The vector becomes infected by feeding on the body fluid of an infected person/animal; the pathogen develops and multiplies in the vector; the vector infects a healthy person while feeding on their body fluids.
What happens to the pathogen in the biological method of transfer?
A part of its life cycle takes place in the body of the vector.
Name examples of micro-organisms carried biologically by insect vectors.
The virus that causes yellow fever (carried by Aedes mosquito) and Trypanosoma (carried by tsetse-fly)
Name examples of water-borne diseases.
Typhoid fever
Name examples of food-borne diseases.
Salmonella food poisoning
Name examples of diseases transmitted by vectors.
Malaria
What is the best way to control micro-organisms and the diseases they cause?
Proper sanitation and hygiene.
Name practices that constitute proper sanitation and hygiene.
Clean environment
What is sterilization?
The complete destruction of all living micro-organisms
Name common methods of sterilization.
Heat
How does heat kill micro-organisms?
By coagulating their protoplasm.
What are the two forms of heat used for sterilization?
Dry heat and moist heat.
What are the methods of applying dry heat for sterilization?
Flaming
What is flaming used for?
Sterilizing loops
What temperature and duration are used in a hot air oven for sterilization?
160°C for at least one hour.
What is incineration used for?
Burning and destroying materials like soiled dressings
What are the methods of applying moist heat for sterilization?
Boiling and autoclaving.
How does boiling kill micro-organisms?
By coagulating their protoplasm.
How long should materials be boiled to kill most vegetative cells?
10-20 minutes.
Does boiling kill spores?
No.
What is the most reliable method of sterilization?
Autoclaving.
What is an autoclave?
A metallic chamber similar to a pressure cooker.
What are the conditions used in an autoclave for sterilization?
121°C at 15 lbs pressure per square inch for 15-20 minutes.
How does an autoclave kill spores?
By using high temperature and pressure.
What is filtration used for in sterilization?
Removing micro-organisms from liquids and gases that would be destroyed by heat.
What are examples of materials that are sterilized by filtration?
Blood serum
What types of filters are used for sterilization?
Seitz
What is the pore size of membrane filters used for sterilizing liquids?
0.22 μm.
What is radiation used for in sterilization?
Killing micro-organisms by destroying their DNA.
What are the two types of radiation used for sterilization?
Ultraviolet (UV) radiation and ionizing radiation.
What is UV radiation used for?
Sterilizing surfaces and air in enclosed areas.
Does UV radiation penetrate materials well?
No.
What is ionizing radiation used for?
Sterilizing disposable medical equipment and food.
Does ionizing radiation penetrate materials well?
Yes.
What are examples of ionizing radiation?
X-rays
What are the three main groups of chemical substances used to control/kill micro-organisms?
Disinfectants
What are disinfectants?
Chemical substances that kill micro-organisms but are too harmful to be applied to living tissues.
Where are disinfectants used?
On non-living objects and surfaces like floors
Name examples of disinfectants.
Sodium hypochlorite (bleach)
What are antiseptics?
Chemical substances that prevent the growth and multiplication of micro-organisms and can be safely applied to living tissues.
Where are antiseptics used?
On the skin and mucous membranes to prevent infections.
Name examples of antiseptics.
Tincture of iodine
What are antibiotics?
Chemical substances produced by living micro-organisms that inhibit the growth of or destroy other micro-organisms.
Where are antibiotics used?
Internally or externally to treat infections in humans and animals.
Name examples of antibiotics.
Penicillin
What are the factors that influence the effectiveness of a chemical agent?
Concentration
How does concentration affect the effectiveness of a chemical agent?
Higher concentrations are usually more effective.
How does time of exposure affect the effectiveness of a chemical agent?
Longer exposure times are more effective.
How does temperature affect the effectiveness of a chemical agent?
Higher temperatures usually increase effectiveness.
How does organic matter affect the effectiveness of a chemical agent?
It can interfere with the activity of the agent.
What is pasteurization?
A method of killing harmful micro-organisms in milk and other fluids by heating them at a high temperature for a short time.
What are the two methods of pasteurization?
The holder method and the flash method.
Describe the holder method of pasteurization.
Milk is heated to 63°C for 30 minutes.
Describe the flash method of pasteurization.
Milk is heated to 72°C for 15 seconds.
Does pasteurization sterilize milk?
No
What is the shelf life of pasteurized milk?
2-3 days if refrigerated.
What is ultra-high temperature (UHT) treatment?
Heating milk to 132°C for 1-2 seconds.
Does UHT treatment sterilize milk?
Yes.
What is the shelf life of UHT-treated milk?
Several months at room temperature.
What is the importance of micro-organisms in nature?
Decomposition
What is decomposition?
The breakdown of dead organic matter into simpler substances.
What type of micro-organisms are mainly responsible for decomposition?
Saprophytic bacteria and fungi.
What is the importance of decomposition?
It releases nutrients back into the environment for use by plants.
What is nutrient cycling?
The movement of essential elements between living organisms and the environment.
Name important nutrient cycles in which micro-organisms play a vital role.
The carbon cycle and the nitrogen cycle.
What is the role of micro-organisms in the carbon cycle?
They are involved in photosynthesis and decomposition
What is the role of micro-organisms in the nitrogen cycle?
They are involved in nitrogen fixation
Name examples of food products produced using micro-organisms.
Yoghurt
Name examples of industrial processes that utilize micro-organisms.
Production of antibiotics
What is immunity?
The ability of the body to resist infection.
What are the two main types of immunity?
Innate immunity and acquired immunity.
What is innate immunity?
The natural resistance to infection that an individual is born with.
Name examples of innate immunity.
Skin
How does the skin provide innate immunity?
It forms a physical barrier that prevents the entry of micro-organisms.
How do mucous membranes provide innate immunity?
They trap micro-organisms and prevent them from entering the body.
How do body secretions provide innate immunity?
They contain enzymes and other substances that kill micro-organisms.
What are phagocytic cells?
Cells that engulf and destroy micro-organisms.
What is acquired immunity?
The immunity that develops after exposure to a micro-organism.
What are the two types of acquired immunity?
Active immunity and passive immunity.
What is active immunity?
The immunity that develops when the body produces its own antibodies in response to an infection or vaccination.
How long does active immunity usually last?
Long-lasting.
What is passive immunity?
The immunity that develops when the body receives antibodies from another source.
How long does passive immunity usually last?
Short-lived.
Name examples of passive immunity.
Antibodies passed from mother to foetus through the placenta
What is an antiserum?
A serum containing antibodies against a specific micro-organism.
What is vaccination?
The process of introducing a weakened or killed micro-organism into the body to stimulate the production of antibodies and provide active immunity.
What is a vaccine?
A preparation of weakened or killed micro-organisms used for vaccination.
What is the importance of vaccination?
It provides protection against specific infectious diseases.
Name examples of diseases that can be prevented by vaccination.
Measles
What is the importance of micro-organisms to humans?
They are both beneficial and harmful.
Name beneficial activities of micro-organisms.
Decomposition
Name harmful activities of micro-organisms.
Food spoilage and causing diseases.
What should we do to control the harmful activities of micro-organisms?
Practice proper sanitation and hygiene.
Front
Back
What are the beneficial activities of micro-organisms?
Decomposition
What is the harmful activity of micro-organisms?
Food spoilage.
What is food spoilage?
The contamination of food by micro-organisms
What types of food are easily spoilt by micro-organisms?
Those rich in water and nutrients.
Name the groups of micro-organisms commonly associated with food spoilage.
Bacteria and fungi.
What are the general effects of food spoilage?
Changes in appearance
Name examples of bacteria that cause food spoilage.
Pseudomonas
Name examples of fungi that cause food spoilage.
Rhizopus
What does Pseudomonas cause in food?
Slimy appearance and fishy odour in meat and fish.
What does Bacillus cause in food?
Ropiness in bread.
What does Clostridium cause in food?
Sour odour in canned foods.
What does Proteus cause in food?
Rotting of meat.
What does Rhizopus cause in food?
Soft rot of fruits and vegetables.
What does Aspergillus cause in food?
Discoloration of groundnuts and maize.
What does Penicillium cause in food?
Blue mould on oranges.
What are the economic losses due to food spoilage?
Reduced food quality
What are the health hazards associated with food spoilage?
Food poisoning due to toxins produced by spoilage micro-organisms.
What are the general methods of preserving food?
Physical methods and chemical methods.
Name physical methods of food preservation.
Drying
How does drying preserve food?
By removing water
Name traditional methods of drying food.
Sun-drying.
Name modern methods of drying food.
Oven-drying and freeze-drying.
What types of food are preserved by drying?
Grains
How does freezing preserve food?
By lowering the temperature
At what temperature is food usually frozen for preservation?
-18°C to -25°C.
Does freezing kill micro-organisms?
No
What types of food are preserved by freezing?
Meat
How does heating preserve food?
By killing micro-organisms and inactivating enzymes.
Name methods of food preservation that use heating.
Pasteurization
What types of food are preserved by heating?
Milk
How does irradiation preserve food?
By using ionizing radiation to kill micro-organisms and insects.
What types of food are preserved by irradiation?
Spices
Name chemical methods of food preservation.
Using salt
How does salt preserve food?
By creating a high salt concentration
What types of food are preserved by salting?
Fish and meat.
How does sugar preserve food?
By creating a high sugar concentration
What types of food are preserved by using sugar?
Jams
How does vinegar preserve food?
By increasing the acidity
What types of food are preserved by pickling in vinegar?
Vegetables and fish.
How does smoke preserve food?
By containing chemicals that kill micro-organisms and dry the food surface.
What types of food are preserved by smoking?
Fish and meat.
What are chemical preservatives?
Chemical substances added to food to prevent microbial growth and spoilage.
Name examples of chemical preservatives.
Benzoic acid
What are the advantages of using chemical preservatives?
They are effective at low concentrations and do not significantly alter the taste or appearance of food.
What are the disadvantages of using chemical preservatives?
Some people may be allergic to them
What are the different types of microscopy techniques used to study living cells?
Brightfield microscopy
What is brightfield microscopy?
The most common type of microscopy
What is darkfield microscopy?
A technique that enhances contrast by illuminating the specimen from the side
What is phase-contrast microscopy?
A technique that enhances contrast in transparent specimens by converting differences in refractive index into differences in brightness.
What is fluorescence microscopy?
A technique that uses fluorescent dyes to label specific molecules in the cell
What is confocal microscopy?
A type of fluorescence microscopy that uses a laser to scan the specimen and create a three-dimensional image.
What is electron microscopy?
A technique that uses electrons instead of light to create images
What are the different types of electron microscopy?
Transmission electron microscopy (TEM) and scanning electron microscopy (SEM).
What is the purpose of transmission electron microscopy (TEM)?
To view the internal structures of cells.
What is the purpose of scanning electron microscopy (SEM)?
To view the surface structures of cells.
What are the different techniques used to prepare specimens for microscopy?
Fixation
What is fixation?
A process that preserves the structure of cells and tissues.
What are the different types of fixation?
Chemical fixation (using chemicals like formaldehyde) and physical fixation (using heat or freezing).
What is staining?
A process that uses dyes to color cells and tissues
What are the different types of staining techniques?
Simple stains and differential stains.
What is sectioning?
The process of cutting thin slices of tissue for microscopy.
What are the different types of sectioning techniques?
Manual sectioning (using a razor blade) and microtomy (using a microtome).
What are the different types of culture media used to grow animal cells?
Natural media (derived from biological fluids or tissues) and synthetic media (chemically defined media).
What are the essential components of a tissue culture medium?
Nutrients
What are growth factors?
Substances that stimulate cell growth and division.
What are hormones?
Chemical messengers that regulate cell function.
What is a buffering system?
A system that maintains the pH of the culture medium.
What are the different types of tissue culture?
Primary culture (cells isolated directly from tissue) and cell line (cells that can be grown indefinitely in culture).
What are the different types of cell lines?
Finite cell lines (cells that have a limited lifespan) and continuous cell lines (cells that can be grown indefinitely).
What are the applications of tissue culture?
Studying cell biology
What are the ethical considerations associated with tissue culture?
Concerns about the use of animal cells and the potential for contamination.
What are the different types of micro-organisms that can contaminate tissue cultures?
Bacteria
How can contamination of tissue cultures be prevented?
Using aseptic techniques and sterilizing equipment and media.
What are the different methods used to detect contamination in tissue cultures?
Microscopy
What are the different methods used to treat contamination in tissue cultures?
Antibiotics
What are the different types of cell culture vessels?
Petri dishes
What are the different types of incubators used to grow cells?
CO2 incubators and water-jacketed incubators.
What is a CO2 incubator?
An incubator that maintains a constant temperature
What is a water-jacketed incubator?
An incubator that uses a water jacket to maintain a stable temperature.
What are the different types of cell counting methods?
Hemocytometer and automated cell counters.
What is a hemocytometer?
A specialized slide used to count cells under a microscope.
What are automated cell counters?
Instruments that use electronic or optical methods to count cells.
What are the different methods used to measure cell viability?
Dye exclusion assays and metabolic assays.
What are dye exclusion assays?
Methods that use dyes to distinguish between live and dead cells.
What are metabolic assays?
Methods that measure the metabolic activity of cells.
What are the different methods used to separate cells?
Centrifugation
What is centrifugation?
A technique that uses centrifugal force to separate cells based on their density.
What is filtration?
A technique that uses filters to separate cells based on their size.
What is chromatography?
A technique that separates cells based on their chemical properties.
What are the different methods used to store cells?
Cryopreservation and refrigeration.
What is cryopreservation?
The process of freezing cells to preserve them for long periods.
What is refrigeration?
The process of storing cells at low temperatures (4°C) to slow down their metabolism.
What are the different types of safety equipment used in a microbiology laboratory?
Gloves
What are the different types of safety procedures used in a microbiology laboratory?
Handwashing
What are the different types of waste generated in a microbiology laboratory?
Sharps
How should sharps be disposed of?
In puncture-resistant containers.
How should biohazardous waste be disposed of?
In designated biohazard bags and autoclaved before disposal.
How should chemical waste be disposed of?
According to local regulations.
What is the importance of following safety procedures in a microbiology laboratory?
To protect laboratory workers and prevent the spread of infection.
