A mannose-sensitive haemagglutinin (MSHA)-like pilus promotes attachment of Pseudoalteromonas tunicata cells to the surface of the green alga Ulva australis

Department of Chemistry and Biochemistry, University of California, San Diego, San Diego, California, United States
Microbiology (Impact Factor: 2.84). 11/2006; 152(Pt 10):2875-83. DOI: 10.1099/mic.0.29158-0
Source: PubMed

ABSTRACT This study demonstrates that attachment of the marine bacterium Pseudoalteromonas tunicata to the cellulose-containing surface of the green alga Ulva australis is mediated by a mannose-sensitive haemagglutinin (MSHA-like) pilus. We have identified an MSHA pilus biogenesis gene locus in P. tunicata, termed msh/1/2JKLMNEGFBACDOPQ, which shows significant homology, with respect to its genetic characteristics and organization, to the MSHA pilus biogenesis gene locus of Vibrio cholerae. Electron microscopy studies revealed that P. tunicata wild-type cells express flexible pili peritrichously arranged on the cell surface. A P. tunicata mutant (SM5) with a transposon insertion in the mshJ region displayed a non-piliated phenotype. Using SM5, it has been demonstrated that the MSHA pilus promotes attachment of P. tunicata wild-type cells in polystyrene microtitre plates, as well as to microcrystalline cellulose and to the living surface of U. australis. P. tunicata also demonstrated increased pilus production in response to cellulose and its monomer constituent cellobiose. The MSHA pilus thus functions as a determinant of attachment in P. tunicata, and it is proposed that an understanding of surface sensing mechanisms displayed by P. tunicata will provide insight into specific ecological interactions that occur between this bacterium and higher marine organisms.

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Available from: Doralyn Dalisay, Jul 28, 2015
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    • "There were 17 genes in a cluster coding for a mannose-sensitive hemagglutinin (MSHA) biogenesis locus (Online Resource 5) in NW4327. The MSHA pili operon structure of NW4327 closely resembled that of P. tunicata (Dalisay et al. 2006) in which the MSHA pilus played a role in the attachment of the bacterium to abiotic and living surfaces (Dalisay et al. 2006). While NW4327 lacked the mshF gene found in P. tunicata, both strains contained the two mshI genes. "
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    ABSTRACT: Sponge diseases have increased dramatically, yet the causative agents of disease outbreaks have eluded identification. We undertook a polyphasic taxonomic analysis of the only confirmed sponge pathogen and identified it as a novel strain of Pseudoalteromonas agarivorans. 16S ribosomal RNA (rRNA) and gyraseB (gyrB) gene sequences along with phenotypic characteristics demonstrated that strain NW4327 was most closely related to P. agarivorans. DNA-DNA hybridization and in silico genome comparisons established NW4327 as a novel strain of P. agarivorans. Genes associated with type IV pili, mannose-sensitive hemagglutinin pili, and curli formation were identified in NW4327. One gene cluster encoding ATP-binding cassette (ABC) transporter, HlyD and TolC, and two clusters related to the general secretion pathway indicated the presence of type I secretion system (T1SS) and type II secretion system (T2SS), respectively. A contiguous gene cluster of at least 19 genes related to type VI secretion system (T6SS) which included all 13 core genes was found. The absence of T1SS and T6SS in nonpathogenic P. agarivorans S816 established NW4327 as the virulent strain. Serine proteases and metalloproteases of the classes S8, S9, M4, M6, M48, and U32 were identified in NW4327, many of which can degrade collagen. Collagenase activity in NW4327 and its absence in the nonpathogenic P. agarivorans KMM 255(T) reinforced the invasiveness of NW4327. This is the first report unambiguously identifying a sponge pathogen and providing the first insights into the virulence genes present in any pathogenic Pseudoalteromonas genome. The investigation supports a theoretical study predicting high abundance of terrestrial virulence gene homologues in marine bacteria.
    Marine Biotechnology 04/2015; 17(4). DOI:10.1007/s10126-015-9627-y · 3.15 Impact Factor
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    • "Here we have begun to fill this knowledge gap by investigating the mechanisms that facilitate interactions between the marine bacterium P. tunciata with its macroalgal host. We found that a P. tunicata ptlL32 strain attached with a greatly reduced capacity to the biotic surfaces (Figures 2–4), a finding that is in line with previous reports indicating that the colonization of U. australis by P. tunicata involves multiple adhesins (Dalisay et al., 2006; Thomas et al., 2008). "
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    Frontiers in Microbiology 07/2014; 5:323. DOI:10.3389/fmicb.2014.00323 · 3.94 Impact Factor
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    • "While the major fraction of these ORFs code for hypothetical proteins with unknown functions and hence await future identification, the eight unique epibiont genes Cag_0614, Cag_0615, Cag_0616, Cag_1239, Cag_1408, Cag_ 1570, Cag_1919 and Cag_1920 match known bacterial virulence factors and therefore provide promising targets for future functional studies of the molecular coupling across the interface of the partner cells in phototrophic consortia. Of particular interest are the genes suggested to encode haemagglutinins, as the latter are typically associated with the cell membrane, are exposed at the cell surface and mediate the attachment of pathogenic bacteria to their host cells (Relman et al., 1989; Kajava et al., 2001); other homologues are involved in the adherence of non-pathogenic bacteria to surfaces and other microorganisms (Dalisay et al., 2006). A second conspicuous group of unique genes in the epibiont genome are the seven ORFs Cag_0648 to Cag_0650, Cag_0665, Cag_0668, Cag_0673 and Cag_ 0675, which are closely located to each other on the genome (Table S1). "
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