The Rcs regulon in Proteus mirabilis: implications for motility, biofilm formation, and virulence

Abstract

The overall role of the Rcs phosphorelay in Proteus mirabilis is largely unknown. Previous work had demonstrated that the Rcs phosphorelay represses the flhDC operon and activates the minCDE cell division inhibition system. To identify additional cellular functions regulated by the Rcs phosphorelay, an analysis of RNA-seq data was undertaken. In this report, the results of the RNA-sequencing are discussed with an emphasis on the predicted roles of the Rcs phosphorelay in swarmer cell differentiation, motility, biofilm formation, and virulence. RcsB is shown to activate genes important for differentiation and fimbriae formation, while repressing the expression of genes important for motility and virulence. Additionally, to follow up on the RNA-Seq data, we demonstrate that an rcsB mutant is deficient in its ability to form biofilm and exhibits enhanced virulence in a Galleria mellonella waxworm model. Overall, these results indicate the Rcs regulon in P. mirabilis extends beyond flagellar genes to include those involved in biofilm formation and virulence. Furthermore, the information presented in this study may provide clues to additional roles of the Rcs phosphorelay in other members of the Enterobacteriaceae.

Pathogenesis of Proteus mirabilis Infection

“…The next three studies (127, 139, 140) compared gene expression for targeted mutants with their isogenic parent strain using RNA-seq. In addition to the aforementioned microarray study, broth-cultured and swarmer cells have also been compared by RNA-seq using the BB2000 lab strain (127).…”

“…The Rcs phosphorelay is a repressor of swarming and an activator of biofilm formation (139, 140, 142–144). RNA-seq was used to compare a broth-cultured rcsB mutant with its isogenic parent strain PM7002 (139, 140).…”

“…RNA-seq was used to compare a broth-cultured rcsB mutant with its isogenic parent strain PM7002 (139, 140). In this condition, the rcsB mutant undergoes inappropriate elongation that is similar to the fliL phenotype.…”

“…Logically, regulators of the above biofilm factors, such as the RcsBCD phosphorelay (RcsD is also known as RsbA) (140, 177, 279) and RNA chaperone Hfq (164), control biofilm formation. Surface hydrophobicity, mediated by lipopolysaccharide (LPS) (53, 280, 281) and capsular polysaccharides (282–284), influence both initial surface colonization and biofilm maturation.…”

Peer pressure from a Proteus mirabilis self-recognition system controls participation in cooperative swarm motility:

“…We also observed a decrease in transcripts for many genes associated with protein synthesis, such as the 50S ribosomal protein rplT and 30S ribosomal protein rpsP, along with ribosomal-associated elongation factors such as EF-Tu. Several genes involved in respiration, including those of the F o F 1 -ATP synthase, also had significantly fewer transcripts as did those transcripts for different virulence-associated protein families (26)(27)(28)(29)(30)(31), such as hpmA, umoA, and zapD. Overall, fewer genes had an increased relative abundance as compared to the control strains: 109 genes in CCS06, 56 genes in CCS02, and 332 genes in co-swarmed Δids, respectively.…”