BIRGIT PRUESS, Ph.D.
Research Assistant Professor
RESEARCH INTERESTS
It was recently demonstrated that Escherichia coli flhD is not only responsible for the induction
of flagellar genes, but also involved in another process which occurs as cells enter stationary
phase, the reduction of the cell division rate. flhD is one of two genes, flhD and flhC, in the
master operon at the top of the hierarchy of flagella expression. It was demonstrated that flhD
but not flhC mutants grown in tryptone broth, continued to divide at a rate typical for mid-expoential growth at a time where wild-type cells started to reduce their cell division rate.
Mutant cells were smaller than wild-type cells as they entered stationary phase (see Fig). It
was demonstrated that this was due to an inability to sense the depletion of serine from the
medium which signals wild-type cells to reduce their cell division rate. The signal cascade is
believed to include phosphorylation of OmpR, the response regulator of the osmoregulation
system, by acetyl phosphate, one of the intermediates which occur during the degradation of
serine.
Transposon mutagenesis revealed multiple targets of flhD. We believe that flhD is a global
regulator involved in many stationary phase processes.
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