title: Quorum-sensing regulation of a capsular polysaccharide receptor for the Rhodobacter capsulatus gene transfer agent (RcGTA).
abstract: The gene transfer agent produced by Rhodobacter capsulatus (RcGTA) resembles a small tailed bacteriophage that packages almost random genomic DNA segments that may be transferred to other R. capsulatus cells. Gene transfer agents are produced by a number of prokaryotes; however, no receptors have been identified. We investigated the RcGTA recipient capability of wild-type R. capsulatus cells at different culture growth phases, and found that the frequency of RcGTA-dependent acquisition of an allele increases as cultures enter the stationary phase. We also found that RcGTA adsorption to cells follows a similar trend. RcGTA recipient capability and adsorption were found to be dependent on the GtaR/I quorum-sensing (QS) system. Production of an extracellular polysaccharide was found to be regulated by GtaR/I QS, as was production of the cell capsule. A number of QS-regulated putative polysaccharide biosynthesis genes were identified, and mutagenesis of two of these genes, rcc01081 and rcc01932, yielded strains that lack a capsule. Furthermore, these mutants were impaired in RcGTA recipient capability and adsorption, as was a non-encapsulated wild-type isolate of R. capsulatus. Overall, our results indicate that capsular polysaccharide is a receptor for the gene transfer agent of R. capsulatus, RcGTA.
authors.affiliation: Department of Microbiology and Immunology, The University of British Columbia, Vancouver, BC, Canada.
authors.forename: Cedric A
authors.initials: CA
authors.lastname: Brimacombe
authors.forename: Aaron
authors.initials: A
authors.lastname: Stevens
authors.forename: Daniel
authors.initials: D
authors.lastname: Jun
authors.forename: Ryan
authors.initials: R
authors.lastname: Mercer
authors.forename: Andrew S
authors.initials: AS
authors.lastname: Lang
authors.forename: J Thomas
authors.initials: JT
authors.lastname: Beatty
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D011135:Polysaccharides, Bacterial / Q000378:metabolism*; D053038:Quorum Sensing; D016354:Rhodobacter capsulatus / Q000235:genetics* / Q000502:physiology; D014161:Transduction, Genetic
chemical_list: D001426:Bacterial Proteins; D011135:Polysaccharides, Bacterial