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  • 1
    In: Molecular Microbiology, April 2010, Vol.76(2), pp.409-427
    Description: attachment is mediated by the holdfast, a complex of polysaccharide anchored to the cell by HfaA, HfaB and HfaD. We show that all three proteins are surface exposed outer membrane (OM) proteins. HfaA is similar to fimbrial proteins and assembles into a high molecular weight (HMW) form requiring HfaD, but not holdfast polysaccharide. The HfaD HMW form is dependent on HfaA but not on holdfast polysaccharide. We show that HfaA and HfaD form homomultimers and that they require HfaB for stability and OM translocation. All three proteins localize to the late pre‐divisional flagellar pole, remain at this pole in swarmer cells, and localize at the stalk tip after the stalk is synthesized at the same pole. Hfa protein localization requires the holdfast polysaccharide secretion proteins and the polar localization factor PodJ. An mutant is much more severely deficient in adherence and holdfast attachment than and mutants. An , double mutant phenocopies either single mutant, suggesting that HfaB is involved in holdfast attachment beyond secretion of HfaA and HfaD. We hypothesize that HfaB secretes HfaA and HfaD across the outer membrane, and the three proteins form a complex anchoring the holdfast to the stalk.
    Keywords: Proteins ; Polysaccharides;
    ISSN: 0950-382X
    E-ISSN: 1365-2958
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  • 2
    In: Molecular Microbiology, September 2003, Vol.49(6), pp.1671-1683
    Description: The differentiating bacterium produces two different cell types at each cell division, a motile swarmer cell and an adhesive stalked cell. The stalked cell harbours a stalk, a thin cylindrical extension of the cell surface. The tip of the stalk is decorated with a holdfast, an adhesive organelle composed at least in part of polysaccharides. The synthesis of the stalk and holdfast occur at the same pole during swarmer cell differentiation. Mutations in the gene cluster had been shown to disrupt the attachment of the holdfast to the tip of the stalk, but the role of individual genes was unknown. We used fusions of various DNA fragments from the region to show that these genes form an operon. In order to analyse the relative contribution of the different genes to holdfast attachment, mutations were constructed for each gene. was not required for holdfast attachment or binding to surfaces. The and mutants shed some holdfast material into the surrounding medium and were partially deficient in binding to surfaces. Unlike and mutants, mutants were still able to form rosettes efficiently. Cells with insertions in were unable to bind to surfaces, and lectin binding studies indicated that the mutants had the strongest holdfast shedding phenotype. We determined that HfaB and HfaD are membrane‐associated proteins and that HfaB is a lipoprotein. Purification of stalks and cell bodies indicated that both HfaB and HfaD are enriched in the stalk as compared to the cell body. These results suggest that HfaB and HfaD, and probably HfaA, serve to anchor the holdfast to the tip of the stalk.
    Keywords: Bacterial Adhesion ; Bacterial Proteins -- Metabolism ; Caulobacter Crescentus -- Cytology ; Membrane Proteins -- Metabolism;
    ISSN: 0950-382X
    E-ISSN: 1365-2958
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  • 3
    Language: English
    In: Molecular microbiology, January 2019, Vol.111(1), pp.254-268
    Description: Clusters of Neisseria meningitidis (Nm) urethritis among primarily heterosexual males in multiple US cities have been attributed to a unique non-encapsulated meningococcal clade (the US Nm urethritis clade, US_NmUC) within the hypervirulent clonal complex 11. Resistance to antimicrobial peptides (AMPs) is a key feature of urogenital pathogenesis of the closely related species, Neisseria gonorrhoeae. The US_NmUC isolates were found to be highly resistant to the model AMP, polymyxin B (PmB, MICs 64-256 µg ml ). The isolates also demonstrated stable subpopulations of heteroresistant colonies that showed near total resistant to PmB (MICs 384-1024 µg ml ) and colistin (MIC 256 µg ml ) as well as enhanced LL-37 resistance. This is the first observation of heteroresistance in N. meningitidis. Consistent with previous findings, overall PmB resistance in US_NmUC isolates was due to active Mtr efflux and LptA-mediated lipid A modification. However, whole genome sequencing, variant analyses and directed mutagenesis revealed that the heteroresistance phenotypes and very high-level AMP resistance were the result of point mutations and IS1655 element movement in the pilMNOPQ operon, encoding the type IV pilin biogenesis apparatus. Cross-resistance to other classes of antibiotics was also observed in the heteroresistant colonies. High-level resistance to AMPs may contribute to the pathogenesis of US_NmUC.
    Keywords: Peptides – Analysis ; Chromosomes – Analysis ; Urethritis – Genetic Aspects ; Urethritis – Analysis ; Microbial Drug Resistance – Genetic Aspects ; Microbial Drug Resistance – Analysis;
    ISSN: 0950382X
    E-ISSN: 1365-2958
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