Growth - increase in size of the population as well as
of individual cells
Binary fission, a form of asexual reproduction in which
cells replicates their chromosomal DNA as they increases in size,
form a septum between the chromosome copies, then separate
(divides into two cells of roughly equal size
Generation time is the length of time required for a
microbial population to double (varies from 5 min to 12 h in
actively growing cultures)
Measuring microbial growth by increases in:
mass - a broth culture of cells can be grown, then
dehydrated and the dry weight of the cells determined by
weighing them
number of cells in a broth culture, three approaches
can be taken:
direct count - cells are counted using a Neubauer
chamber (which allows one to count the number of cells in a
known volume of fluid)
viable count - cells are diluted and plated on a
suitable culture medium, then the number of resulting
colonies counted
total count - the number of cells can be
estimated by determining the turbidity of the culture using
a colorimeter
Growth curve - phases:
lag - cells get ready to synthesize components
needed for growth
log (or exponential) - rapid proliferation
(exponential or logarithmic)
stationary - cell proliferation is balanced by cell
death caused by nutrient depletion or accumulation of metabolic
by-products
