topic 4.1 microbial population growth

how do bacteria reproduce?

binary fission

what happens during binary fission?

cell elongates and chromosomal DNA is copied

elongated cell pinches inwards at the membrane and cell wall until cell divides into 2

binary fission can occur in which eukaryotes?

amoeba and paramecium

what is the definition of microbial growth?

the increase in cell numbers, cell density or biomass in a microbial population over time.

how are microbes usually cultivated?

they are cultivated in batch culture of closed system

what are the factors to consider in each phase of growth curve? (hint: nutrients)

level of nutrients available

what are the factors to consider in each phase of growth curve? (hint: physical space)

amount of physical space available, is there sufficient space or is there overcrowding

what are the factors to consider in each phase of growth curve? (hint: toxic waste products)

level of toxic waste products, metabolic waste products produced by growing cells

what are the factors to consider in each phase of growth curve? (hint: cell density)

cell density, total cell density vs live cell density

how do we prolong the exponential phase of the microbial population?

fed batch and continuous culture

what is fed batch?

fresh media can bed added to the culture which provides more nutrients and dilute metabolic wastes

what is continuous culture?

it is an open system where the volume, cell density, nutrients and wastes levels remained constant and cells are growing at constant rate.

what is an open system?

fresh media is continuously added to the culture while spent media is removed at the same rate.

what is generation time

the time taken for one generation to double

what is the formula for calculating microbial growth?

Nt = N0 2^(t/g)

what does Nt mean?

the cell number after time (t)

what does N0 mean?

the initial cell number