Microbiology Flashcards by Natalie chan

What does the flagellum do in a bacteria?

Helps with motility

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what does the pillus do in a bacteria

Allows attachment to surfaces and allows transfers of plasmids for conjugation

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what does the circular DNA in a bacteria do

Genes which codes for proteins and controls characteristics of the bacteria

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What does the plasma membrane in a bacteria do

Acts as a barrier, controls what goes in and what goes out.

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What do the ribosomes in the bacteria do

protein synthesis

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what does the capsule do in a bacteria

Protects the bacteria, allows the bacteria to stick on surfaces, or on other bacteria and prevents the bacteria from desiccation (drying)

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what does the cell wall do in a bacteria

prevents lysis if in hypotonic solution. also made of murein (peptidoglycan)

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what does the plasmids do in bacteria

its a small circular piece of DNA that contains extra bacterial genes

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how to prokaryotes reproduce

binary fission (mitosis)

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What do these following words mean?
bacillus
coccus
spirillum
diplo
strepto
staphylo

bacillus - rod shaped
coccus - spherical (ball)
spirillum - spiral
diplo - in pairs
strepto - in chains
staphylo - in clumps

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example of a good bacteria

Lactobacillus, used for preparation of fermented foods. like yeast.

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features of a gram postive bacteria

thick layer of peptidoglycan
stains purple
sensitive to penicillin
no lipopolysaccharide

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example of a gram postive bacteria

MRSA (staphylococcus)

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Features of a gram negative bacteria

stains red
not sensitive to penicillin
thinner layer of peptidoglycan
extra lipopolysaccharide layer

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example of a gram negative bacteria

E. Coli.

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How to gram stain

1 - loop full of bacteria on glass slide
2 - air-dry and heat fix through flame (about 2-3 times)
3 - add crystal violet and leave on for 30 secs.
4 - drain and wash with water
5 - add lugols iodine and keep it on for 1 minute
6 - flood with acetone/alcohol (ONLY FOR 30-45 seconds)
7 - add safranin (counter stain) and keep it on for 30 secs.
8 - drain and wash away with water

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what are the metabolic requirements for a bacteria and why?

Temperature - optimum temperature = works best
pH - optimum pH = works best
Oxygen - aerobic respiration
Glucose - anaerobic respiration and carbon source
Nitrogen - needed to make proteins and amino acids
Vitamins and minerals - nutrients.

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at what temperature do pathogens grow best at?

37 degrees (body temperature)

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what are bacterias that can grow at lower temperatures called

saprotrophs

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what are bacterias that can grow at cold places called and what are bacterias that can grow at hot places called?

cold places - psychophiles

hot places - extremophiles

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what are obligate aerobes?

bacteria that can grow with oxygen

what are obligate anaerobes

bacteria that can grow without oxygen

what are facultative anaerobes

bacteria that grow best with oxygen but can grow without.

what are the two types of growth media

liquid broth and solid agar.

what do the growth medias need to contain to make bacterial growth efficient

- carbon source (glucose) - nitrogen source (amino acids) - vitamins and minerals

what are the important aseptic techniques

- autoclaved glassware (at 121 degress) - disinfect work surface before and after experiment - open bottle with one hand - bunsen burner to create rising air current - bunsen burner to flame mouth of bottle and inoculating loop - make sure there is minimum exposure of the disk - tape lid to dish - incubate at 25 degrees

why do we need to use aseptic techniques

prevent contamination of the culture from bacterias outside and infection from the organism being used

how does UV lights kill bacteria?

disrupts the DNA of a microorganism from reproduction (killing them) and disrupts the chemical bonds that hold the DNA together.

what examples are used in the experiment, pour plates and why?

M. luteus (gram positive), E. Col (gram negative) - used because they are not pathogenic.

what do bacteriostatic and bactericidal antibiotics do?

bacteriostatic inhibits protein synthesis. and bactericidal weakens the cell wall of bacteria therefore killing it as lysis occurs.

describe lag phase

new environment means the cells are adjusting the more different the environment the longer the lag phase. cell is active but is not dividing meaning there is no population growth

describe exponential phase (log)

population doubles per unit time from lag phase. bacteria are growing and dividing rapidly.

describe stationary phase

cell production is equal to cell death and nutrients start to run out so population growth is no longer possible.

describe death phase

decline of cell population because of accumulated toxins which cause the death of microbes that produced toxins.

what are metabolites

products of cellular metabolic processes.

what are primary metabolites

produced as part of normal cell activity, needed for growth or waste products e.g. proteins, co2, ammonia

what are secondary metabolites

they are only produced in the stationary phase to kill competitors

why count bacteria

environmental health monitoring - check for e.coli in sea water at bathing beaches water supply - to see if water is contaminated at the end of the purification process monitor growth in fermenters

what is direct count?

counting all bacteria

what is total count

counting all cells including dead and living

what is viable count

counting all living cells

what does the acid/base inlet do in a fermenter

it allows acid plus base to be added to make optimum pH as the bacteria produce co2 which makes the solution more acidic.

what does the pressure gauge do in a fermenter

it controls the pressure when the pressure is increased due to co2

what does the motor and impeller do

it mixes the medium and stops the medium from settling

what does the steam do in a fermenter

it sterilizes the fermenter and medium

what does the temperature and ph probe do

makes sure that the fungi and bacteria are working at its optimum.

what does the cooling jackert and cold water outlet/inlet do in a fermenter

cools the medium if it gets hotter as heat is a by-product of respriation

what does the oxygen probe / sparger do

provides oxygen of the aeroobic bacteria

what do the filters do in the inolets/outlets in fermenters

they prevent anything from going in (prevents contamination)

what are primary metabolites and give info about them

primary metabolites are produced to be used in metabolic reactions they are oroduced during log phase and a continuous fermenters would be used. an exmaple would be insulin

what are secondary metabolites and give info about them

they are produced when organisms are in stressed conditions when nutrients are limiting they are produced during the stationary phase and batch fermenters are used e.g penicillin