Growth Flashcards
(31 cards)
What is minimal media?
- media that only contains the absolutely necessary components required for growth
What is defined medium?
- every component and its quantity are known
What is undefined medium?
- some components/quantities are not known exactly
What is a rich medium?
- contains components allowing for a high growth rate that is not strictly necessary for basic growth
- tends to be rich in nutrients, complex mixtures: unknown mixture of ingredients
What is turbidity and what does it measure?
- it is cloudiness; the amount of light passing through a culture
- more bacteria = more light scattered
- not the most accurate, can’t tell alive from the dead
What is the viable cell count method for measuring growth?
- dilute sample culture, spread dilutions onto solid plate medium
- only living cells will grow on plates
- accurate for number of alive cell count
What the direct cell count method for measuring growth?
- load sample of culture into counting chamber and view in the microscope
- count cells directly
- can’t really determine living vs dead
What kind of growth pattern is often graphed when measuring bacterial growth?
- because cells reproduce through binary fission, you get exponential growth
- seen better through a log scale gragh
What is the lag phase in the overall growth phase of bacteria?
- when cells are adapting to new environment
- not really any activity
What is the exponential phase of the overall growth phase of bacteria?
- cells grow and divide exponentially at consistent rate
- see exp. growth
What is the exponential phase of the overall growth phase of bacteria?
- cells grow and divide exponentially at a consistent rate
- see exp. growth
What is the stationary phase of the growth phase in bacteria?
- cells are no longer actively growing
- nutrients are used, waste builds up
- cells undergo change to survive
What is the death/long-term stationary phase of the cell growth phase?
- cell population lowers exponentially
- different cell variants become dominant in succession
What is the death/long-term stationary phase of the cell growth phase?
- cell population lowers exponentailly
- different cell variant become damominnat in succession
What is balanced cell growth?
- in exp. phase, cell components increase by the same proportion
- mean cell size is constant in balanced growth
- balanced cell growth requires an unchanging environment, low cell density
What is a chemostat?
- a device to allow continuous balanced growth through constant dilution
What are the equations needed for exp. growth?
- look them up idiot
How does temperature affect cell growth rate?
- each species has its own optimum growth temperature
- more leeway under the optimal temp than above it, so worse growth once optimal temp has been passed
What happens to cells at the extremes of temperature?
- highest temperatures: proteins denature
- lowest temperatures: weakened hydrophobic interactions, alter protein
How do microbes adjust to lower temperatures?
- easier to adjust to lower temperatures
- proteins and fatty acid composition made a little more unstable to complete said reactions
How do microbes adjust to higher temperatures?
- proteins constructed to withstand denaturing
- chaperone proteins/ Heat shock proteins to hep fold and keep folded properly
- DNA- binding proteins to hold it together
- Reverse Gyrase: promotes supercoiling- tightens DNA double helix
How can some microbes grow in saturating concentrations of salt?
- two stresses
1) dries out cell
2) lowers cell turgor pressure - Most cells respond by increasing their internal concentration of solutes
How does the process of binary division start in gram-negative and gram-positive cells?
- gram-negative: bacteria generally male a constriction at mid-cell
- gram-positive: may or may not constrict., can just square off usually
What is the process of regulating chromosome segregation when binary fission occurs?
- draw it out
- ParA grabs ParB which has ParS, and essentially pulls the chromosomes to opposite poles of the cell
