title: Role of the Umo proteins and the Rcs phosphorelay in the swarming motility of the wild type and an O-antigen (waaL) mutant of Proteus mirabilis.
abstract: Proteus mirabilis is a Gram-negative bacterium that exists as a short rod when grown in liquid medium, but during growth on surfaces it undergoes a distinct physical and biochemical change that culminates in the formation of a swarmer cell. How P. mirabilis senses a surface is not fully understood; however, the inhibition of flagellar rotation and accumulation of putrescine have been proposed to be sensory mechanisms. Our lab recently isolated a transposon insertion in waaL, encoding O-antigen ligase, that resulted in a loss of swarming but not swimming motility. The waaL mutant failed to activate flhDC, the class 1 activator of the flagellar gene cascade, when grown on solid surfaces. Swarming in the waaL mutant was restored by overexpression of flhDC in trans or by a mutation in the response regulator rcsB. To further investigate the role of the Rcs signal transduction pathway and its possible relationship with O-antigen surface sensing, mutations were made in the rcsC, rcsB, rcsF, umoB (igaA), and umoD genes in wild-type and waaL backgrounds. Comparison of the swarming phenotypes of the single and double mutants and of strains overexpressing combinations of the UmoB, UmoD, and RcsF proteins demonstrated the following: (i) there is a differential effect of RcsF and UmoB on swarming in wild-type and waaL backgrounds, (ii) RcsF inhibits UmoB activity but not UmoD activity in a wild-type background, and (iii) UmoD is able to modulate activity of the Rcs system.
authors.affiliation: Department of Microbiology and Immunology, Emory University, Atlanta, Georgia, USA.
authors.forename: Randy M
authors.initials: RM
authors.lastname: Morgenstein
authors.forename: Philip N
authors.initials: PN
authors.lastname: Rather
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D019729:Carbon-Oxygen Ligases / Q000235:genetics* / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D008074:Lipoproteins / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D011513:Proteus mirabilis / Q000201:enzymology* / Q000235:genetics / Q000502:physiology*
chemical_list: D001426:Bacterial Proteins; D008074:Lipoproteins; D019729:Carbon-Oxygen Ligases