6.2.1 Serial Dilutions + Bacterial Growth Curves Flashcards
Number of colonies in a sample =
Number of colonies x dilution factor
Serial dilution is…
Diluting a solution repeatedly to decrease the ratio, eg 1:10 to 1:100,000 ratio after 4 dilutions
Lag phase of bacterial growth curve?
Bacteria start to grow; beginning of graph
What happens in lag phase?
Bacteria acclimatise to new environment; no cell division occurs; produce primary metabolites; metabolically active
Primary metabolites?
Chemicals needed to live
Exponential phase of bacterial growth?
Log phase; bacteria divide at a constant rate
Stationary phase?
Growth stops; theoretical growth is exponential; secondary metabolites made; rate of division = death
Growth in stationary phase stops because…
Nutrients / space is limited; toxins are produced, eg pH changes
Death phase?
Bacteria die faster than they multiply; closed system; batch fermentation
Log can be used to…
Calculate bacterial growth
Formula for bacterial populations?
N = N,0 x 2^n
N = N,0 x n^2
N= number of bacteria after divisions; N,0 = initial number of bacteria; n = number of divisions / generations
