title: Genetic analysis of the CDI pathway from Burkholderia pseudomallei 1026b.
abstract: Contact-dependent growth inhibition (CDI) is a mode of inter-bacterial competition mediated by the CdiB/CdiA family of two-partner secretion systems. CdiA binds to receptors on susceptible target bacteria, then delivers a toxin domain derived from its C-terminus. Studies with Escherichia coli suggest the existence of multiple CDI growth-inhibition pathways, whereby different systems exploit distinct target-cell proteins to deliver and activate toxins. Here, we explore the CDI pathway in Burkholderia using the CDIIIBp1026b system encoded on chromosome II of Burkholderia pseudomallei 1026b as a model. We took a genetic approach and selected Burkholderia thailandensis E264 mutants that are resistant to growth inhibition by CDIIIBp1026b. We identified mutations in three genes, BTH_I0359, BTH_II0599, and BTH_I0986, each of which confers resistance to CDIIIBp1026b. BTH_I0359 encodes a small peptide of unknown function, whereas BTH_II0599 encodes a predicted inner membrane transport protein of the major facilitator superfamily. The inner membrane localization of BTH_II0599 suggests that it may facilitate translocation of CdiA-CTIIBp1026b toxin from the periplasm into the cytoplasm of target cells. BTH_I0986 encodes a putative transglycosylase involved in lipopolysaccharide (LPS) synthesis. ∆BTH_I0986 mutants have altered LPS structure and do not interact with CDI⁺ inhibitor cells to the same extent as BTH_I0986⁺ cells, suggesting that LPS could function as a receptor for CdiAIIBp1026b. Although ∆BTH_I0359, ∆BTH_II0599, and ∆BTH_I0986 mutations confer resistance to CDIIIBp1026b, they provide no protection against the CDIE264 system deployed by B. thailandensis E264. Together, these findings demonstrate that CDI growth-inhibition pathways are distinct and can differ significantly even between closely related species.
authors.affiliation: Department of Molecular, Cellular and Developmental Biology, University of California Santa Barbara, Santa Barbara, California, United States of America.
authors.forename: Sanna
authors.initials: S
authors.lastname: Koskiniemi
authors.affiliation: Department of Molecular, Cellular and Developmental Biology, University of California Santa Barbara, Santa Barbara, California, United States of America.
authors.forename: Fernando
authors.initials: F
authors.lastname: Garza-Sánchez
authors.affiliation: Department of Molecular, Cellular and Developmental Biology, University of California Santa Barbara, Santa Barbara, California, United States of America.
authors.forename: Natasha
authors.initials: N
authors.lastname: Edman
authors.affiliation: Department of Molecular, Cellular and Developmental Biology, University of California Santa Barbara, Santa Barbara, California, United States of America.
authors.forename: Swarnava
authors.initials: S
authors.lastname: Chaudhuri
authors.affiliation: Department of Molecular, Cellular and Developmental Biology, University of California Santa Barbara, Santa Barbara, California, United States of America.
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Poole
authors.affiliation: Department of Genome Sciences, Box 355065, University of Washington, Seattle, Washington, United States of America.
authors.forename: Colin
authors.initials: C
authors.lastname: Manoil
authors.affiliation: Department of Molecular, Cellular and Developmental Biology, University of California Santa Barbara, Santa Barbara, California, United States of America; Biomolecular Science and Engineering Program, University of California Santa Barbara, Santa Barbara, California, United States of America.
authors.forename: Christopher S
authors.initials: CS
authors.lastname: Hayes
authors.affiliation: Department of Molecular, Cellular and Developmental Biology, University of California Santa Barbara, Santa Barbara, California, United States of America; Biomolecular Science and Engineering Program, University of California Santa Barbara, Santa Barbara, California, United States of America.
authors.forename: David A
authors.initials: DA
authors.lastname: Low
mesh_terms: D000595:Amino Acid Sequence; D001422:Bacterial Adhesion; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics / Q000378:metabolism; D058947:Bacterial Secretion Systems; D001427:Bacterial Toxins / Q000096:biosynthesis; D016957:Burkholderia pseudomallei / Q000235:genetics* / Q000378:metabolism; D002876:Chromosomes, Bacterial; D003260:Contact Inhibition / Q000235:genetics*; D003593:Cytoplasm / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D008070:Lipopolysaccharides / Q000096:biosynthesis; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation; D019897:Periplasm / Q000378:metabolism; D021381:Protein Transport; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013045:Species Specificity
chemical_list: D001425:Bacterial Outer Membrane Proteins; D058947:Bacterial Secretion Systems; D001427:Bacterial Toxins; C503914:BamA protein, E coli; C503242:CdiA protein, E coli; C513104:CdiB protein, E coli; D029968:Escherichia coli Proteins; D008070:Lipopolysaccharides; D008565:Membrane Proteins; D026901:Membrane Transport Proteins