title: The InhA metalloproteases of Bacillus cereus contribute concomitantly to virulence.
abstract: The virulence of Bacillus cereus requires that bacteria have the capacity to colonize their host, degrade specific tissues, and circumvent the host immune system. To study this aspect of pathogenesis, we focused on three metalloproteases, InhA1, InhA2, and InhA3, which share more than 66% identity. The expression of these metalloprotease genes was assessed by transcriptional fusions with a lacZ reporter gene. The expression profiles suggest a complementary time course of InhA production. Indeed, the genes are simultaneously expressed but are oppositely controlled during stationary phase. We constructed single and multiple inhA mutants and assessed the bacterial locations of the proteins as well as their individual or additive roles in macrophage escape and toxicity, antibacterial-peptide cleavage, and virulence. InhA1, a major component of the spore exosporium, is the only InhA metalloprotease involved in bacterial escape from macrophages. A mutant lacking inhA1, inhA2, and inhA3 shows a strong decrease in the level of virulence for insects. Taken together, these results show that the InhA metalloproteases of B. cereus are important virulence factors that may allow the bacteria to counteract the host immune system.
authors.affiliation: Unité Génétique Microbienne et Environnement, INRA, La Minière, 78285 Guyancourt Cedex, France. nalini.ramarao@jouy.inra.fr.
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Guillemet
authors.forename: Céline
authors.initials: C
authors.lastname: Cadot
authors.forename: Seav-Ly
authors.initials: SL
authors.lastname: Tran
authors.forename: Marie-Hélène
authors.initials: MH
authors.lastname: Guinebretière
authors.forename: Didier
authors.initials: D
authors.lastname: Lereclus
authors.forename: Nalini
authors.initials: N
authors.lastname: Ramarao
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001409:Bacillus cereus / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development / Q000472:pathogenicity*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D012831:Bombyx / Q000382:microbiology; D002478:Cells, Cultured; D015964:Gene Expression Regulation, Bacterial; D007814:Larva / Q000382:microbiology; D008264:Macrophages / Q000276:immunology / Q000382:microbiology; D045726:Metalloproteases / Q000378:metabolism*; D051379:Mice; D008969:Molecular Sequence Data; D009154:Mutation; D010802:Phylogeny; D017386:Sequence Homology, Amino Acid
chemical_list: D001426:Bacterial Proteins; D045726:Metalloproteases