FSCN 2021 Lecture 7: 18 February
24 Feb 2019
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Document Summary
At optimal growth conditions, e. coli can double in about 20 minutes. Growth is an exponential process for bacteria. A bacterial growth curve illustrates the dynamics of growth. The logarithmic (log) phase: find materials and replicate exponentially (exponential growth phase) Cell will have the most atp in this phase. The stationary phase (used all of nutrients- like used all of carbon) (some bacteria can eat brother or sister ) The death phase (some cells will die, but some will remain viable) Fresh media can drop and then another area allows it to come out. Cells are in logarithmic phase because nutrients are continuously feed and can stay in logarithmic stage. Calculation: number of colonies on plate x reciprocal of dilution of sample= number of bacteria/ml. Based upon dilution level, you can estimate how many colony forming units there were in the original culture. After incubation, count colonies on plates that have 25-250 colonies (cfus) Foods have certain allowable number of bacteria.
