title: Identification of non-flagellar genes involved in swarm cell differentiation using a Bacillus thuringiensis mini-Tn10 mutant library.
abstract: Swarming is a social phenomenon that enables motile bacteria to move co-ordinately over solid surfaces. The molecular basis regulating this process is not completely known and may vary among species. Insertional mutagenesis of a swarming-proficient Bacillus thuringiensis strain was performed, by use of the transposon mini-Tn10, to identify novel genetic determinants of swarming that are dispensable for flagellation, swimming motility, chemotaxis and active growth. Among the 67 non-swarming mutants obtained, six were selected that showed no defect in flagellar assembly and function, chemotaxis or growth rate. Sequence analysis of DNA flanking the transposon insertion led to the identification of previously uncharacterized genes that are involved in the development of swarming colonies by B. thuringiensis and that are highly conserved in all members of the Bacillus cereus sensu lato group. These genes encode non-flagellar proteins with putative activity as sarcosine oxidase, catalase-2, amino acid permease, ATP-binding cassette transporter, dGTP triphosphohydrolase and acetyltransferase. Functional analysis of two of the isolated mutants demonstrated that swarming differentiation depends on the intracellular levels of the osmoprotectant glycine betaine and on the quantity of synthesized phenazine secondary metabolites. The finding that proteins involved in diverse physiological processes have a role in swarming motility underlines the complexity of the molecular mechanisms governing this behaviour in B. thuringiensis.
authors.affiliation: Dipartimento di Patologia Sperimentale, Biotecnologie Mediche, Infettivologia ed Epidemiologia, Università di Pisa, via San Zeno 35-39, 56127 Pisa, Italy.
authors.forename: Sara
authors.initials: S
authors.lastname: Salvetti
authors.affiliation: Dipartimento di Patologia Sperimentale, Biotecnologie Mediche, Infettivologia ed Epidemiologia, Università di Pisa, via San Zeno 35-39, 56127 Pisa, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Celandroni
authors.affiliation: Dipartimento di Biologia, Sezione di Microbiologia, Università di Pisa, via San Zeno 35-39, 56127 Pisa, Italy.
authors.forename: Mara
authors.initials: M
authors.lastname: Ceragioli
authors.affiliation: Dipartimento di Biologia, Sezione di Microbiologia, Università di Pisa, via San Zeno 35-39, 56127 Pisa, Italy.
authors.forename: Sonia
authors.initials: S
authors.lastname: Senesi
authors.affiliation: Dipartimento di Patologia Sperimentale, Biotecnologie Mediche, Infettivologia ed Epidemiologia, Università di Pisa, via San Zeno 35-39, 56127 Pisa, Italy.
authors.forename: Emilia
authors.initials: E
authors.lastname: Ghelardi
mesh_terms: D001413:Bacillus thuringiensis / Q000235:genetics* / Q000254:growth & development / Q000302:isolation & purification / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D002633:Chemotaxis; D002874:Chromosome Mapping; D004251:DNA Transposable Elements; D004269:DNA, Bacterial / Q000235:genetics; D015723:Gene Library; D005798:Genes, Bacterial; D005816:Genetic Complementation Test; D016254:Mutagenesis, Insertional; D009154:Mutation; D010619:Phenazines / Q000032:analysis; D010641:Phenotype; D050879:Sarcosine Oxidase / Q000378:metabolism; D017422:Sequence Analysis, DNA
chemical_list: D001426:Bacterial Proteins; D004251:DNA Transposable Elements; D004269:DNA, Bacterial; D010619:Phenazines; D050879:Sarcosine Oxidase