Chapter 4 (Book) Microbial Growth Flashcards
planktonic cells
free-living organisms that grow and multiply on their own
binary fission
one parental cell splits into two equal daughter cells
growth rate
rate of increase in cell numbers/biomass is proportional to population size at a given time
exponential growth
starting with any # of organisms (No), what is the number of organisms after n generations
No x 2^n
generation time
the constant interval at which bacteria divide in an environment with unlimited resources
doubling time
generation time for cells in culture
the length of the generation time depends on what
bacterial species
medium
temperature
pH
growth constant rate (k)
number of generations per unit time
why doesn’t exponential growth last forever
nutrient consumption and toxic by-products slow growth rate
batch bulture
no fresh medium is added in incubation
nutrients decline and waste products accumulate during growth
4 stages of growth
lag phase
log phase
stationary phase
death phase
lag phase
phase when cells don’t divide
cells prepare machinery for growth
log phase
exponential growth occurs at maximum rate
stationary phase
rate of cell division equals rate of cell death
shut down growth machinery and turn on stress responses
death phase
logarithmic death
number of cells that die is proportional to number of cells that existed in the beginning of the time period
continuous culture
fresh medium constantly added, and old constantly removed
allows log phase for a long time
chemostat
continuous culture system where there is a limited amount of an essential nutrient
increasing flow rate increases amount of nutrient available
biofilm
specialized surface-attached collaborative communities of bacteria
when do biofilms form
when nutrients are plentiful
what happens when nutrients become scarce, biofilm
individuals detach from the community to forage for new sources of nutrients
signals for formation of biofilms
pH
temperature
oxygen levels
formation of a biofilm
signal causes planktonic cells to attach to a surface via pilli or adhesion structures
more cells attach and they spread out
the community talks to each other by sending chemical signals
bacteria faced with environmental stress undergo…
complex molecular reprogramming
endospore
gram-pos mostly
metabolically inactive spore that is resistant to heat and desiccation
formed b/c of starvation
SASP
small acid-soluble proteins
found in spores to protect DNA
germination
genetic response wakes up a spore to release a normal vegetative cell
cyanobacteria differentiate into nitrogen-fixing ________
heterocysts - special cells that function in nitrogen fixation
every 10th cell becomes one
starvation can induce differentiation into ________ bodies
fruiting
gram-neg mostly… aggregation of 100,000 cells
use a gliding motility (pilus) to travel
actinomycetes form _____ and ______
mycelia, sporangia – like fungi
germ tube emerges from a germinating spore
forms branches that grow along the surface of a food source
