Role of ChiRP, a type IV pilus, in chitin surface colonization and the environmental survival of Vibrio cholerae

• Applicant: Dr. Melanie Blokesch
• Subject Area: Metabolism, Biochemistry and Genetics of Microorganisms
• Term: from 2005 to 2007
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 5452339

Vibrio cholerae is the causative agent of cholera. Between outbreaks of human disease, it resides in natural aquatic habitats attached to the chitin-containing exoskeletons of crustaceae. Microarray expression profiling experiments and the study of mutants led to the identification of genes predicted to be required for the surface colonization, degradation of chitin, transport and metabolic assimilation of degradation products of chitin. Amongst these genes were twelve encoding components for the biogenesis and function of ChiRP, a chitin-regulated type IV pilus. PilA, predicted to correspond to the major repeating subunit of the ChiRP pilus fiber, was found to contribute significantly to the survival and growth of V. cholerae on a natural chitin surface. The objective of this proposal is to learn how ChiRP confers this chitin surface colonization phenotype. Two models are proposed: (i) ChiRP binds chitin and is co-localized at the bacterial pole with the type II chitinase secretion apparatus, thus focusing chitinase secretion on the chitin surface; or (ii) the repetitive extrusion and retraction of ChiRP allows V. cholerae to crawl along the chitin surface, leading to effective colonization of the entire surface area. To test these models, the work proposed below will address the following questions: Does ChiRP emanate from the bacterial pole and if so, is the pilus assembly complex co-localized with the type II chitinase secretion apparatus at the old pole of the cell? Does ChiRP bind chitin? Is ChiRP required for translocation across a chitin surface? If so, are the two predicted ATPases (PilB and PilM) of the ChiRP assembly complex necessary for this process? The results of this investigation will provide information on how V. cholerae persists in aquatic environments and may identify novel functions for the type IV pilus family.

• DFG Programme: Research Fellowships
• International Connection: USA
• Host: Professor Dr. Gary K. Schoolnik