LECTURE 9 Flashcards
what is asynchronous growth and what does the plot look like?
asynchronous: timing of cell divisions is random
the plot is a smooth exponential curve
(or a straight line when you take the logarithm)
how does the population of unicellular organisms increase during active growth?
increases exponentially (2^n)
what is synchronous growth and what does the plot look like?
all the cells divide at the same time
step wise growth plot
what is generation time?
period required for a cell to enlarge, divide, and produce two daughter cells
how can generation time vary?
varies across bacteria
all cells in a population have the same doubling time, since same growth conditions for all
varies with the availability of nutrients
less nutrients, time increases
accumulation of toxic metabolic compounds, time increases
when nutrients are all consumed growth stops
what are the phases of growth on the growth curve?
what is the lag phase?
time for cells to adjust to fresh new medium
start or adjust metabolism (protein synthesis, DNA replication)
start dividing
what is the exponential/log phase?
nutrients are not in limiting amounts
cell divide at max speed
lowest doubling time
what is the stationary phase (plateau)
gradual switch
nutrient concentration is limiting and toxic waste accumulates
cells divide slower and eventually stop
doubling time increases gradually
what is the death phase?
nutrients completely consumed
cells stop rowing
start to burst and die, but not all of them
what are some reasons that could lead to a longer lag phase (adjustment period)?
how does a chemostat work?
continuous supply of fresh medium
the metering pump can change the rate of suppling the medium
culture vessel where bacteria constantly grow at the same speed
overflow tube
what does the graph of growth look like in a chemostat
what are the conditions used in a chemostat?
what are the different uses of continuous cultures?
