Microbiology Flashcards
What are the four main groups of microorganism?
- bacteria
- viruses
- protozoa
- fungi
Which of the microorganisms are eukaryotes?
- fungi
- protozoa
Which of the microorganisms are prokaryotes?
- bacteria
What are the features of bacteria?
- prokaryotes / no true nucleus
- contain cytoplasm
- have flagellum (some)
- DNA is in circular strand
- peptidoglycan cell wall
- lack of membrane-bound organelles
What are the features of viruses?
- non-living & acellular
- protective shell called a capsid, contains genetic material
- rely on the host to reproduce
- very small, much smaller than bacteria
- viral envelope surrounds capsid
- shapes - helical, complex & polyhedron
What are the features of fungi?
- eukaryotic
- disperse by producing spores
- saprophytic
- reproduce sexually and asexually
- cell walls of chitin
- form hyphae (multicellular)
- many = mycelium
What are the features of protozoa?
- eukaryotic
- unicellular
- can reproduce asexually and sexually (think it’s mostly asexual)
- heterotrophic
- some have flagella
- can be multinucleate
What are the main differences between bacteria and viruses?
- bacteria are larger
- bacteria are prokaryotic cells, viruses are acellular
- bacteria have a cell wall made of peptidoglycan or liposaccharide, viruses have a capsid
- bacteria have ribosomes, viruses do not
- bacteria reproduce asexually, viruses require a host cell
What are the similarities between bacteria and viruses?
- do not have a nucleus
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Label the bacterial cell
What is the structure of the bacterial cell wall?
- contains peptidoglycan - made from polysaccharides cross-linked with unusual peptides
- can be gram positive or gram negative
What is the function of the bacterial cell wall?
- great mechanical strength
- responsible for strength, rigidity, shape
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What is the structure of the bacterial plasma membrane?
- phospholipid
- phosphate heads
- fatty acid chains
What is the function of the bacterial plasma membrane?
- selectively permeable
- barrier
- protective
- controls metabolism of the cell
What is the structure of the bacterial flagella?
- long & thin
- made of protein
- attached to the cell through the cell wall & the membrane
- could have one or many
What is the function of the bacterial flagella?
- movement
What is the structure of the bacterial capsule?
- capsule is located outside the cell wall
- usually consists of polysaccharides
What is the function of the bacterial capsule?
- provide strength
- protects against the body’s defences
- increases resistance to disinfectants and antibiotics
What is the structure of the bacterial pili?
- thin rigid fiber
- made of protein
- protrudes from the bacterial cell surface
- smaller than flagella
- densely packed
What is the function of the bacterial pili?
- responsible for adhesion
- allows bacteria to stick together to form clumps
- stick to mucous membranes
- allows to attach to human cells to spread disease
What is the function of the bacterial cytoplasm?
- where metabolism, and replication are carried out
What is the structure of the bacterial cytoplasm?
- viscous fluid
- contains nuclear mass and ribosomes
What is the structure of a bacterial inclusion?
- numerous inclusion bodies, or granules, in the bacterial cytoplasm
- never enclosed by a membrane
What is the function of a bacterial inclusion?
- storage vessels.
- Glycogen is stored as a reserve of carbohydrate and energy.
What is the structure of the bacterial mesosome?
- Mesosomes or chondrioids are folded invaginations in the plasma membrane of bacteria
What is the structure of the bacterial ribosomes?
- two subunits
- smaller than eukaryotic ribosomes
What is the function of the bacterial ribosomes?
- protein synthesis
What is the structure of the bacterial nucleoid?
- irregularly shaped region that contains all or most of the genetic material
- not surrounded by a nuclear membrane
- the genome of prokaryotic organisms generally is a circular double-stranded piece of DNA
What is the function of the bacterial nucleoid?
- contains genetic material
- essential for controlling the activity of the cell and reproduction
- where transcription and replication of DNA take place
What is the difference between gram positive and gram negative bacteria?
- gram negative cell wall contains lipoproteins - give the wall greater strength compared to gram positive.
What occurs during binary fission?
- bacterial cell elongates
- bacteria replicates its DNA
- cell membrane/envelope then pinches inwards around the DNA
- cell membrane meets in the middle
- divide is formed, two distinct cells can be seen
- cells separate to form two separate cells
Is binary fission sexual or asexual?
asexual
How do viruses reproduce?
- attachment - virus binds to a specific receptor on the host cell surface
- penetration - the viral nucleic acid enters the cell
- synthesis of new components - viral nucleic acid takes control of the cell metabolism stopping the cells normal nucleic acid and protein synthesis. Viral nucleic acid is replicated using nucleotides from the host cell. Protein coats are manufactured using amino acids of the host cell.
- assembly - whole virus particles are made when the nucleic acids are surrounded by the protein coats
- release - many viral particles are released when the cell bursts open (lysis) or by slow leakage
Label a growth curve
What occurs during the lag phase of a growth curve?
- slow growth due to time and lack of energy
What occurs during the log phase of a growth curve?
- exponential growth
- lots of nutrient medium
- more cells = more replication = more cells…
What occurs during the stationary phase of a growth curve?
- number of living = number of dying
- nutrients being depleted, toxic products beginning to accumulate
What occurs during the death phase of a growth curve?
- more dying than viable
What factors affect the growth of bacteria?
- nutritional factors
- temperature
- pH
- oxygen concentration
- osmotic requirements
What elements are required for nutrition for bacterial growth?
- nitrogen - for amino acids (proteins)
- carbon - main constituent of cellular material
- potassium - required for chemical reactions within the cell
- magnesium - for chemical reactions
- calcium - for chemical reactions & for endospore production
What are organisms who obtain their energy from light called?
Phototrophs
What are bacterial pigments?
- some bacteria produce pigments during growth
- gives colonies characteristic colour
- might give some bacteria some protection from effects of sunlight
What are bacteria who obtain their energy source from an organic form of carbon called?
Heterotrophs
What are bacteria who obtain their source of energy from inorganic compounds called?
Lithotrophs
What are species who thrive in temperatures between 1-25oC (optimum=<20oC) called?
Psychrophiles
What are species who thrive in temperatures between 20-45oC (optimum= 25-37oC) called?
Mesophiles
What are species who thrive in temperatures betweem 45-65oC (optimum=55-65oC) called?
Thermophiles
What is the optimum growth range of acidophiles?
1 - 5.5
What is the optimum growth range for neutrophiles?
5.5-8
What is the optimum growth range of alkalophiles?
8.5 - 11.5
What do fungi produce spores for?
Fungi produce spores for reproduction.
What do bacteria produce spores for?
Bacteria produce spores for protection.
What does a culture media provide?
A culture media provides the ideal conditions for organisms to grow. It provides the nutritional needs of the organism.
What are culture media used for?
- growth of microorganisms
- identification
- transport of specimens
What are the different types of culture medium?
- selective
- differential
- enriched
Give an example of enriched medium.
Tryptone soy agar (TSA)
What is the purpose of an enriched medium?
- specially fortified to encourage lots of growth
Give an example of selective medium.
mannitol salt agar (MSA).
- used to isolate pathogenic staphylococci
- contains 7.5% NaCl - inhibits growth of most bacteria
- fermentation of agar by staphylococci produces area of yellow
What is the purpose of selective mediums?
used to isolate and identify. Allows certain types of organisms to grow and inhibits the growth of others.
Give an example of differential medium.
Eosin Methylene Blue Agar (EMB agar).
Used to differntiate between organisms that ferment lactose and those that do not.
What is the purpose of differential mediums?
differential mediums are used to differentiate different microorganisms. Contain a dye or chemical that will produce characteristic changes which are used to identify.
What are the advantages of using a liquid media?
- useful for growing batch cultures
What are the disadvantages of using a liquid medium?
- hazardous - more likely to spill
- not easy to count colonies of an organism
What are the advantages of using a solid medium?
- enables growth of clear colonies
- easier to count colonies
- can observe colony growth and characteristics amd use this information to identify organisms
- solid media can be selective or differential, which means that solid medium can grow/identify specific organisms or differentiate between two closely related organisms
What are the disadvantages of using a solid medium?
- not very good at producing batch cultures
What are different ways we can carry out microbial monitoring?
- settle plates
- contact plates and swabs
- active air sampling
- finger dabs
Which media should be present in the agar for settle plates?
Tryptone soy agar (TSA) for total count & Sabouraud dextrose agar (sabs) for yeasts and moulds
Where are contact plates used?
Contact plates are recommended to be used on flat accessible surfaces
Where should surface swabs be used?
Surface swabs should be used when a surface isn’t flat and accessible.
When are finger dabs performed?
Finger dabs are performed at the end of the session.
What are characteristics of a desirable disinfectant?
- cost
- effective on pathogen + on surface
- smells nice
- colour
- availability
What are some different chemical agents for disinfecting?
- phenols
- halogens
- alcohols
- quaternary ammonium compounds
What are the advantages of using phenols?
- work by denaturing proteins and disrupting membranes
- are tuberculocidal
- remain on surfaces long after application
What are the disadvantages of using phenol disinfectants?
- hexachlorphene can cause brain damage
- only used in staphylococcal outbreaks in hospital nurseries
- unpleasant odour
- can cause skin irritation
TRUE or FALSE
Alcohol is bactericidal and fungicidal?
TRUE!
Alcohol is bactericidal and fungicidal,
it is NOT sporicidal.
How do alcohol disinfectants work?
Alcohol denatures proteins and also possibly dissolves membrane lipids
Which are the two most important anti-microbial halogens?
Chlorine and iodine
What is iodine used for?
Iodine is used as a skin antiseptic and kills by oxidising cell constituents.
What are the disadvantages of iodine?
- may damage the skin
- stains the skin
- iodine allergies may result
What is an improved version of iodine?
Iodophor is iodine complexed with an organic carrier. Releases iodine slowly to minimise skin burns and irritation.
What does chlorine kill?
Chlorine destroys bacteria and fungi but not spores.
What is quaternary ammonium compound?
Quaternary ammonium compound is a detergent
What are the advantages of detergents?
- stable
- non-toxic
What are the disadvantages of detergents?
- inactivated by hard water and soap
Define sterility
Sterility is the total absence of viable organisms in an absolute state. In pharmacy achieved by aseptic technique or terminal sterilisation
Define sterilisation
the process that products are subjected to whereby all viable organisms are killed or removed.
Define aseptic technique
Aseptic technique means preparing products from sterile starting materials whilst using procedures that prevent the access of viable organisms into the product.
What are the methods of sterilisation?
- moist heat sterilisation in autoclaves
- dry heat sterilisation
- sterilisation by filtration
- gaseous sterilisation
- sterilisation by radiation
What is the process of moist heat sterilisation in autoclaves?
- 121oC for 15 minutes
- pressure of 15lbs
What is the process of dry heat sterilisation?
- 180oC for at least 30 minutes
- 170oC for at least 1 hour
- 160oC for at least 2 hours
What is a host?
an organism that supports the growth of another organism
What are the features of normal flora?
- do not harm us
- do not cause disease
- large numbers within the body
- perform tasks essential for human survival
Define a pathogen
A pathogen is a microorganism capable of causing disease
What is an opportunistic pathogen?
- generally harmless in normal environment
- can be pathogenic in immunocompromised host
What is an obligate pathogen?
- depend on hosts for key nutrients but live outside host cells
- to be transmitted must cause disease
What is the infectious disease cycle?
pathogen
source
transmission
susceptibility
exit
What is an active carrier?
An active carrier is diagnosed with the disease
What is a convalescent carrier?
recovered from the disease but still harbors pathogen
What is a healthy carrier?
harbors pathogen, asymptomatic (typhoid Mary)
What is an incubatory carrier?
Incubates pathogen, not yet ill
Which ways can pathogens be transmitted?
- airborne
- contact
- vehicle
- vector-borne
What is vehicle transmission?
vehicle is an inanimate object. Spreads the pathogen but is not responsible for the reproduction of it.
What is vector-borne transmission?
refers to living transmitters. Pathogen can exist on either the inside or the outside of the vector.
