title: Quorum sensing-regulated chitin metabolism provides grazing resistance to Vibrio cholerae biofilms.
abstract: Association of Vibrio cholerae with chitinous surfaces of zooplankton is important for its persistence in marine environments, as it provides accessibility to nutrients and resistance to stresses. Predation by heterotrophic protists has a major impact on the survival of V. cholerae. V. cholerae forms biofilms as its main defensive strategy, and quorum sensing (QS) additionally regulates the production of antiprotozoal factors. The role of chitin and QS regulation in V. cholerae grazing resistance was investigated by exposing V. cholerae wild-type (WT) and QS mutant biofilms grown on chitin flakes to the bacteriotrophic, surface-feeding flagellate Rhynchomonas nasuta. V. cholerae formed more biofilm biomass on chitin flakes compared with nonchitinous surfaces. The growth of R. nasuta was inhibited by WT biofilms grown on chitin flakes, whereas the inhibition was attenuated in QS mutant biofilms. The chitin-dependent toxicity was also observed when the V. cholerae biofilms were developed under continuous flow or grown on a natural chitin source, the exoskeleton of Artemia. In addition, the antiprotozoal activity and ammonium concentration of V. cholerae biofilm supernatants were quantified. The ammonium levels (3.5 mM) detected in the supernatants of V. cholerae WT biofilms grown on chitin flakes were estimated to reduce the number of R. nasuta by >80% in add-back experiments, and the supernatant of QS mutant biofilms was less toxic owing to a decrease in ammonium production. Transcriptomic analysis revealed that the majority of genes involved in chitin metabolism and chemotaxis were significantly downregulated in QS mutant biofilms when grown on chitin compared with the WT biofilms.
authors.affiliation: 1] Centre for Marine Biofouling and Bio-Innovation, School of Biotechnology and Biomolecular Science, University of New South Wales, Sydney, New South Wales, Australia [2] Singapore Centre on Environmental Life Sciences Engineering, Nanyang Technological University, Singapore.
authors.forename: Shuyang
authors.initials: S
authors.lastname: Sun
authors.affiliation: Singapore Centre on Environmental Life Sciences Engineering, Nanyang Technological University, Singapore.
authors.forename: Qi Xiang Martin
authors.initials: QX
authors.lastname: Tay
authors.affiliation: 1] Centre for Marine Biofouling and Bio-Innovation, School of Biotechnology and Biomolecular Science, University of New South Wales, Sydney, New South Wales, Australia [2] Singapore Centre on Environmental Life Sciences Engineering, Nanyang Technological University, Singapore [3] School of Biological Sciences, Nanyang Technological University, Singapore.
authors.forename: Staffan
authors.initials: S
authors.lastname: Kjelleberg
authors.affiliation: 1] Singapore Centre on Environmental Life Sciences Engineering, Nanyang Technological University, Singapore [2] School of Biological Sciences, Nanyang Technological University, Singapore.
authors.forename: Scott A
authors.initials: SA
authors.lastname: Rice
authors.affiliation: 1] Centre for Marine Biofouling and Bio-Innovation, School of Biotechnology and Biomolecular Science, University of New South Wales, Sydney, New South Wales, Australia [2] Singapore Centre on Environmental Life Sciences Engineering, Nanyang Technological University, Singapore [3] School of Biological Sciences, Nanyang Technological University, Singapore.
authors.forename: Diane
authors.initials: D
authors.lastname: McDougald
mesh_terms: D000641:Ammonia / Q000378:metabolism / Q000494:pharmacology; D000818:Animals; D000981:Antiprotozoal Agents / Q000494:pharmacology; D018441:Biofilms / Q000254:growth & development; D002686:Chitin / Q000378:metabolism / Q000502:physiology*; D016830:Kinetoplastida / Q000187:drug effects / Q000502:physiology; D053038:Quorum Sensing / Q000235:genetics / Q000502:physiology*; D014734:Vibrio cholerae / Q000254:growth & development / Q000502:physiology*; D015048:Zooplankton / Q000382:microbiology
chemical_list: D000981:Antiprotozoal Agents; D002686:Chitin; D000641:Ammonia