Inactivation of the fis gene leads to reduced growth rate.

The FIS protein (factor for inversion stimulation) is known to activate the transcription of rRNA and tRNA operons in Escherichia coli. In this report the growth behaviour of a fis bacterium was studied under steady-state conditions and in competition experiments with a wild-type bacterium in a chemostat. The growth rate of the fis bacterium was reduced as compared to that of an isogenic wild-type and this reduction increased linearly with increasing growth rate. A similar result was obtained in competition experiments in a chemostat, with the selection factor increasing linearly with the growth rate.