Rapid turnover of FlhD and FlhC, the flagellar regulon transcriptional activator proteins, during Proteus swarming

The enterobacterial flhDC master operon activates expression of the flagell ar biogenesis gene hierarchy and also represses cell division. During Prote us mirabilis differentiation into elongated hyperflagellated swarm cells, f lhDC transcription is strongly but transiently increased. We show that conc entration of the FlhD and FlhC proteins is also tightly controlled at the p osttranslational level. This is achieved by protein degradation, which is m ost severe after differentiation when the half-life of both proteins is ca. 2 min. Degradation is energy dependent and putatively involves the Lon pro tease.