culture methods, bacteria growth, antimicrobial measures Flashcards
What are the types of culture methods and what do they do?
4 types
they all use agar plates
- spread plates
- they are spread evenly over the surface of agar using sterile glass spreader - serial dilution
- helps reduce the cell count to isolate bacteria and get single colonies to analyze, helps you get a pure culture - confluant lawn
- the bacteria is evenly distributed across the plate and this is done to test bacteriophage and diluted to see how bacteria is killed and which bacteriophages killed them - streaking plates
- the goal of this is to get isolated colonies, and the idea of doing this is to be able to analyze it
- T-streaking
what is the growth curve of bacteria and what is occuring?
There’s 4 phases
- lag phase
- bacteria are preparing their cell machinery for growth - log phase
- bacteria start growing exponentially
- the shortest generation time and fastest - stationary phase
- cells stop growing and shut down their growth machinery while turning on stress responses to help retain viability
why do they stop?
- more competition, waste is building, nutrients are decreasing, so growth and death rates even out - death phase
- cells die with a half-life
what is a chemostat?
Chemostat is a bioreactor
- it controls two things
1. growth rates
(flow/dilution rates)
2. population density (limiting the nutrient source)
cells grow consistently in a exponential phase, at a steady state, with a constant cell mass, they will never reach the stationary phase
what are the limits of bacteria growth?
6 limits
- temperature
- pH
- salt concentration
- oxygen
- pressure
- radiation
what are different bacteria classification for temperatures
3 types
- psychrophile
- low temperatures - mesophile
- room temperatures - thermophile
- hot temperatures
what are different bacteria classification for pH
3 types
- acidophile
- like low pH, acidic environments - aciduric
- they dont prefer acidic environments but they can grow in them - alkaliphile
- they grow out of it
- they like less acidic environments
what are different bacteria classification for salt
halophile
- can grow in extreme levels of salt
what are different bacteria classification for oxygen
4 types
- anaerobe
- no oxygen and will die in the presence of oxygen - facultative anaerobe
- can live without oxygen and it can live with it - aerobe
- needs oxygen to live - microaerophile
- just a little amount of oxygen
what are different bacteria classification for pressure
2 types
- Barophile
- prefer high pressure - barotolent
- dont prefer high pressure but can live in it
what are different bacteria classification for radiation
radioresistant
- can resist high amounts of radiation
what are extremophiles and what are some examples of them?
extremophiles can live in extreme conditions
5 examples:
Mono lake
- alkaliphile
- halophile
Deinococcus radiodurans
- radioresistant
- can survive in cold, dehydration, vacuum, acid
Blood falls in Antarctic
- A microbial community trapped in a salty lake beneath a glacier for 2 million years, without light, oxygen, or heat
Grand Prismatic Spring, Yellowstone
- thermophiles
- There’s a ring of organisms that prefer different temperature so the reason why there’s a ring of color is because of these organisms
sea floor hydrothermal vents
- thermophile
- barophile
what are the types of antimicrobial measures and what is it for?
antimicrobial measures help restrict bacterial growth
- refrigeration/freezing
- heat
- endospores may still survive - autoclave
- heat
- steam
- pressure - filtration
- dehydration
- drying
—> no water to grow
- adding sugar or honey
–> too much sugar
—> there are endospores that can grow on honey but our immune system can handle it
- salting
–> too much salt - Acidification
- soy sauce, kimchi, pickles, yogurt - Irradiation
- gamma rays, x rays, electrons, UV light - Vacuum packaging
- removes not all oxygen, not sterile - chemical disinfectants
- alcohol
- hydrogen peroxide
- iodine
- chlorine
- detergent
- phenol (lysol)
