RpoS controls the Vibrio cholerae mucosal escape response.
Vibrio cholerae causes a severe diarrhoeal disease by secreting a toxin during colonization of the epithelium in the small intestine. Whereas the initial steps of the infectious process have been intensively studied, the last phases have received little attention. Confocal microscopy of V. cholerae O1-infected rabbit ileal loops captured a distinctive stage in the infectious process: 12 h post-inoculation, bacteria detach from the epithelial surface and move into the fluid-filled lumen. Designated the "mucosal escape response," this phenomenon requires RpoS, the stationary phase alternative sigma factor. Quantitative in vivo localization assays corroborated the rpoS phenotype and showed that it also requires HapR. Expression profiling of bacteria isolated from ileal loop fluid and mucus demonstrated a significant RpoS-dependent upregulation of many chemotaxis and motility genes coincident with the emigration of bacteria from the epithelial surface. In stationary phase cultures, RpoS was also required for upregulation of chemotaxis and motility genes, for production of flagella, and for movement of bacteria across low nutrient swarm plates. The hapR mutant produced near-normal numbers of flagellated cells, but was significantly less motile than the wild-type parent. During in vitro growth under virulence-inducing conditions, the rpoS mutant produced 10- to 100-fold more cholera toxin than the wild-type parent. Although the rpoS mutant caused only a small over-expression of the genes encoding cholera toxin in the ileal loop, it resulted in a 30% increase in fluid accumulation compared to the wild-type. Together, these results show that the mucosal escape response is orchestrated by an RpoS-dependent genetic program that activates chemotaxis and motility functions. This may furthermore coincide with reduced virulence gene expression, thus preparing the organism for the next stage in its life cycle.
Nielsen
Alex Toftgaard
AT
Division of Infectious Diseases and Geographic Medicine, Department of Medicine, Stanford University School of Medicine, Stanford, California, United States of America.
Dolganov
Nadia A
NA
Otto
Glen
G
Miller
Michael C
MC
Wu
Cheng Yen
CY
Schoolnik
Gary K
GK
D000818:Animals; D001426:Bacterial Proteins / Q000502:physiology*; D002771:Cholera / Q000382:microbiology* / Q000473:pathology; D004195:Disease Models, Animal; D017353:Gene Deletion; D015964:Gene Expression Regulation, Bacterial; D007082:Ileum / Q000382:microbiology / Q000503:physiopathology; D007413:Intestinal Mucosa / Q000382:microbiology* / Q000503:physiopathology; D018613:Microscopy, Confocal; D009068:Movement / Q000502:physiology; D020411:Oligonucleotide Array Sequence Analysis; D012329:RNA, Bacterial / Q000032:analysis; D011817:Rabbits; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012808:Sigma Factor / Q000172:deficiency / Q000502:physiology*; D014734:Vibrio cholerae / Q000502:physiology* / Q000648:ultrastructure
D001426:Bacterial Proteins; D012329:RNA, Bacterial; D012808:Sigma Factor; C069567:sigma factor KatF protein, Bacteria