A NONSWARMING MUTANT OF PROTEUS-MIRABILIS LACKS THE LRP GLOBAL TRANSCRIPTIONAL REGULATOR

Proteus swarming is the rapid cyclical population migration across sur faces by elongated cells that hyper-express flagellar and virulence ge nes. The mini-Tn5 transposon mutant mns2 was isolated as a tight nonsw arming mutant that did not elongate or upregulate flagellar and hemoly sin genes, Individual cell motility was retained but was reduced. The transposon had inserted in the gene encoding the global transcriptiona l regulator Lrp (leucine-responsive regulatory protein), expression bf which was upregulated in differentiating swarm cells, Swarming was re stored to the lrp mutant by artificial overexpression of the flhDC fla gellar regulatory master operon. Lrp may be a key component in generat ing or relaying signals that are required for flagellation arid Swarmi ng, possibly acting through the flhDC operon.