MICRB 265 (October 16, 2013)
Nutrition and Growth (con’t)
It takes E.Coli 40 minutes to replicate its DNA but only 20 minutes to double cell
components… why? Multiple rounds of replication.
o MinE gets concentrated in the middle of the cell and causes the FTSz ring to form
Ring gets pulled through zipA molecule to start cell division.
Growth zone = more and more peptidoglycan being inserted into the cell wall
o Same process for both gram positive and gram negative bacteria.
o How do we go about cell wall extension without breaking it and causing the cell to lyse?
Peptidoglycan precursors brought past the cytoplasmic membrane by
Glycolytic bonds are broken to allow for the insertion of new monomers by
Transpeptidation occurs and penicillin binding proteins are involved.
The viable count of bacteria after inoculation goes through an initial lag phase before any cell
division is seen
o Replicating cell components
o No= cell density once lag phase is over and exponential growth starts
o Time spent in lag phase is not predictable or calculate-able.
Reasons for Lag Phase Age of culture
o The older the cu