Microbiology Flashcards
What does the flagellum do in a bacteria?
Helps with motility
what does the pillus do in a bacteria
Allows attachment to surfaces and allows transfers of plasmids for conjugation
what does the circular DNA in a bacteria do
Genes which codes for proteins and controls characteristics of the bacteria
What does the plasma membrane in a bacteria do
Acts as a barrier, controls what goes in and what goes out.
What do the ribosomes in the bacteria do
protein synthesis
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)
what does the cell wall do in a bacteria
prevents lysis if in hypotonic solution. also made of murein (peptidoglycan)
what does the plasmids do in bacteria
its a small circular piece of DNA that contains extra bacterial genes
how to prokaryotes reproduce
binary fission (mitosis)
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
example of a good bacteria
Lactobacillus, used for preparation of fermented foods. like yeast.
features of a gram postive bacteria
- thick layer of peptidoglycan
- stains purple
- sensitive to penicillin
- no lipopolysaccharide
example of a gram postive bacteria
MRSA (staphylococcus)
Features of a gram negative bacteria
- stains red
- not sensitive to penicillin
- thinner layer of peptidoglycan
- extra lipopolysaccharide layer
example of a gram negative bacteria
E. Coli.
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
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.
at what temperature do pathogens grow best at?
37 degrees (body temperature)
what are bacterias that can grow at lower temperatures called
saprotrophs
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
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
