title: Identification of a luxO-regulated extracellular protein Pep and its roles in motility in Vibrio alginolyticus.
abstract: The fish pathogen Vibrio alginolyticus virulence factors and regulation mechanism are barely known except the quorum sensing regulated extracellular products. In the present study, the cleavable isotope-coded affinity tags (cICATs) were used to analyze the differentially expressed extracellular proteins of V. alginolyticus wild-type and a ΔluxO mutant, and a putative peptidase Pep was identified. Quantitative real-time reverse transcription PCR confirmed that the transcription of pep was down-regulated by LuxO. Furthermore, western blotting demonstrated that the expression of Pep was cell-density dependent and quorum sensing regulated in V. alginolyticus. The pep in-frame mutant abolished the swimming and swarming motility, suggesting that it was involved in motility regulation in V. alginolyticus. In liquid medium, the polar flagellum was observed intact in ∆pep mutant while the chemotaxis related gene cheY, which is a response regulator causing change in direction of flagellar rotation, was down-regulated in ∆pep mutant. When ∆pep mutant was grown on hard agar plate, the lateral flagella disappeared and the transcriptions of flagellar biogenesis genes flaK, fliS, lafK, and lafA were down-regulated in ∆pep mutant. These results suggested that Pep was a luxO-regulated extracellular protein and involved in the motility of V. alginolyticus.
authors.affiliation: State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, 130 Meilong Road, Shanghai, PR China.
authors.forename: Xiaodan
authors.initials: X
authors.lastname: Cao
authors.forename: Qiyao
authors.initials: Q
authors.lastname: Wang
authors.forename: Qin
authors.initials: Q
authors.lastname: Liu
authors.forename: Haopeng
authors.initials: H
authors.lastname: Rui
authors.forename: Huan
authors.initials: H
authors.lastname: Liu
authors.forename: Yuanxing
authors.initials: Y
authors.lastname: Zhang
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D005407:Flagella / Q000235:genetics / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D008969:Molecular Sequence Data; D010447:Peptide Hydrolases / Q000235:genetics / Q000378:metabolism*; D053038:Quorum Sensing; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D044149:Vibrio alginolyticus / Q000201:enzymology / Q000235:genetics / Q000502:physiology*
chemical_list: D001426:Bacterial Proteins; D012097:Repressor Proteins; D010447:Peptide Hydrolases