population growth in a closed culture Flashcards
what is the function of a liquid broth
liquid broth- a sterile liquid which is then mixed with a fixed volume of bacteria
used to grow bacteria on agar plate and then can be measured.
also used in serial dilution
can be inoculated and population size can be measured
what is closed culture
a culture which has no exchange of nutrients or gases with the external environment
what is serial dilution
a technique to compare different densities of population
definition- a sequence of dilutions used to reduce the concentration of a solution. the concentration decreases by the same quantity between each tube.
what is the purpose of serial dilution
to reduce the population density and and achieve an appropriate concentration to investigate the growth of a population of microorganisms
used to count bacteria populations
how do you serially dilute
get multiple test tubes
all test tubes already contain 9cm of distilled, sterile water.
to tube 1- add 1cm of broth culture. (0.1 dilution).
to test tube two- add 1cm of liquid from test tube 1 (0.01 dilution)
to test tube 3- add 1 cm of liquid from test tube 2. (0.001)
to test tube 4- add 1cm of liquid from test tube 3 (0.0001)
10 to the minus 1 strength dilution of broth. to form a 1 in 10 ratio of broth to water,
TO CALCULATE COLONY NUMBERS ON AGAR PLATE. must count the colonies and multiply by 10 to calculate population density in broth.
when are serial dilutions used
counting bacteria colonies/ yeast populations
what happens after the serial dilution is made
a DROP of each dilution can be used to inoculate an agar plate.
what tool is used to spread a drop of broth over a sterile agar plate
sterile glass spreader
describe the predictable pattern of population growth within a closed culture
lag phase
exponential phase
stationary phase
death phase
describe the line on the graph of the exponential phase
steep line on graph going up
describe the line on a population growth graph representing the stationary phase
straight line after the exponential phase
what is the line to show death phase of a growth population graph
a steep declining line after the stationary phase
describe lag phase
early part of population growth
, slow growth.
population size is still small,
ORGANISMS ADJUSTING TO THEIR ENVIRONMENT
what are some examples of lag phase in a closed culture
taking up water
cell growth
switching on and off genes
synthesising specific protein
what protein is an enzyme
globular protein
describe the exponential growth phase/ log phase
organisms have now adjusted
all have enzymes to survive
the population grows rapidly and reproduces
what is stationary phase
no population growth, it has reached its max
phase in batch culture, where most secondary metabolites are produced
where competition for nutrients is highest
reproduction is EQUAL to death rate
what is death phase
lethal waste product concentration increases
nutrients run out
more individuals die
population decrease
what phase are most primary metabolites produced
log phase- phase of growth.
primary metabolite- products produced by microorganims during growth and synthesis
