A cell division regulatory mechanism controls the flagellar regulon in Escherichia coli

The formation of flagella in various thermosensitive (Ts) cell division mutants of Escherichia coli was examined at the nonpermissive temperature. The number of flagella per unit cell length decreased sharply after shifting the culture temperature from 30 degrees to 40 degrees C in the following Ts mutants: ftsC108, ftsD1033, ftsE1181, ftsF1141, ftsG29, ftsZ84, parA110, dnaB42, nrdB, and dnaG. It was found that transcription of genes responsible for the formation and/or function of flagella (hag, fla, mot, che) decreased significantly at 40 degrees C. However, in the ftsI730 mutant at the nonpermissive temperature, or in penicillin G treated wild-type cells, cell division was blocked but formation of flagella continued. Moreover, when the cfcA1 mutation, of a gene involved in coordinating DNA replication and cell division, was introduced into the dnaB42 mutant strain, inhibition of cell division and also of formation of flagella at 40 degrees C was relaxed. These results indicate that the flagellar regulon is under the control of a cell division regulatory mechanism.