title: Distribution of S-layers on the surface of Bacillus cereus strains: phylogenetic origin and ecological pressure.
abstract: Bacillus anthracis, Bacillus cereus and Bacillus thuringiensis have been described as members of the Bacillus cereus group but are, in fact, one species. B. anthracis is a mammal pathogen, B. thuringiensis an entomopathogen and B. cereus a ubiquitous soil bacterium and an occasional human pathogen. In two clinical isolates of B. cereus, in some B. thuringiensis strains and in B. anthracis, an S-layer has been described. We investigated how the S-layer is distributed in B. cereus, and whether phylogeny or ecology could explain its presence on the surface of some but not all strains. We first developed a simple biochemical assay to test for the presence of the S-layer. We then used the assay with 51 strains of known genetic relationship: 26 genetically diverse B. cereus and 25 non-B. anthracis of the B. anthracis cluster. When present, the genetic organization of the S-layer locus was analysed further. It was identical in B. cereus and B. anthracis. Nineteen strains harboured an S-layer, 16 of which belonged to the B. anthracis cluster. All 19 were B. cereus clinical isolates or B. thuringiensis, except for one soil and one dairy strain. These findings suggest a common phylogenetic origin for the S-layer at the surface of B. cereus strains and, presumably, ecological pressure on its maintenance.
authors.affiliation: Toxines et Pathogénie Bactérienne (CNRS URA 2172), Institut Pasteur, 28 rue du Dr Roux, 75724 Paris Cédex 15, France.
authors.forename: T
authors.initials: T
authors.lastname: Mignot
authors.forename: B
authors.initials: B
authors.lastname: Denis
authors.forename: E
authors.initials: E
authors.lastname: Couture-Tosi
authors.forename: A B
authors.initials: AB
authors.lastname: Kolstø
authors.forename: M
authors.initials: M
authors.lastname: Mock
authors.forename: A
authors.initials: A
authors.lastname: Fouet
mesh_terms: D001408:Bacillus anthracis / Q000737:chemistry / Q000145:classification / Q000235:genetics; D001409:Bacillus cereus / Q000737:chemistry* / Q000145:classification / Q000235:genetics; D001413:Bacillus thuringiensis / Q000737:chemistry / Q000145:classification / Q000235:genetics; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics; D015139:Blotting, Southern; D015153:Blotting, Western; D004269:DNA, Bacterial; D004463:Ecology; D008562:Membrane Glycoproteins / Q000737:chemistry* / Q000235:genetics; D010802:Phylogeny; D013045:Species Specificity
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D008562:Membrane Glycoproteins; C055764:S-layer proteins