A SWARMING-DEFECTIVE MUTANT OF PROTEUS-MIRABILIS LACKING A PUTATIVE CATION-TRANSPORTING MEMBRANE P-TYPE ATPASE

The motile TnphoA mutant IC24 of Proteus mirabilis U6450 generates an aberrant swarming colony, and was shown to be impaired in swarm cell d ifferentiation. i.e. cell elongation and hyperflagellation, causing de layed and slower population migration across a solid growth medium. Le vels of transcript from the flagellin filament gene fliC, the flagella r master operon flhDC and the leucine-responsive regulatory protein ge ne Irp. a regulator of swarming differentiation. were reduced in IC24 mutant swarm cells. The transposon had inserted into a gene encoding a putative P-type ATPase closely related to those transporting cations across bacterial membranes. This ppa gene ((P) under bar roteus (P) un der bar-type (A) under bar TPase) was maximally expressed in different iated swarm cells. The data suggest an effect of ion homeostasis on sw arm cell differentiation. possibly mediated via the Irp-flhDC pathway.