Observations on the Growth Phases of Escherichia coli, American Type ‘B’

SUMMARY: Observations on the growth phases of Escherichia coli (Bacterium coli), American type ‘B’, on aerated media are reported. On casein-casein-yeast (CCY) medium the culture passes through the following phases: (a) an initial stationary phase; (b) a logarithmic lag phase; (c) a phase of rapid cell division; (d) a phase of equal division and growth rates; (e) a phase of diminishing growth and division rates. The average cell weight increases regularly through phases (a) and (b) to a maximum. It falls during phase (c) to a lower value at phase (d) and decreases finally to its initial value when the growth rate decreases more slowly than the division rate during phase (e). Similar phases can be recognized during growth on 2 % peptone. The onset of the phase of rapid cell division appears to be stimulated by the concentration of cell material.