title: Quorum sensing regulation of the two hcp alleles in Vibrio cholerae O1 strains.
abstract: BACKGROUND
  The type VI secretion system (T6SS) has emerged as a protein secretion system important to several gram-negative bacterial species. One of the common components of the system is Hcp, initially described as a hemolysin co-regulated protein in a serotype O17 strain of Vibrio cholerae. Homologs to V. cholerae hcp genes have been found in all characterized type VI secretion systems and they are present also in the serotype O1 strains of V. cholerae that are the cause of cholera diseases but seemed to have non-functional T6SS.
  
  
  RESULTS
  The serotype O1 V. cholerae strain A1552 was shown to express detectable levels of Hcp as determined by immunoblot analyses using polyclonal anti-Hcp antiserum. We found that the expression of Hcp was growth phase dependent. The levels of Hcp in quorum sensing deficient mutants of V. cholerae were compared with the levels in wild type V. cholerae O1 strain A1552. The expression of Hcp was positively and negatively regulated by the quorum sensing regulators HapR and LuxO, respectively. In addition, we observed that expression of Hcp was dependent on the cAMP-CRP global transcriptional regulatory complex and required the RpoN sigma factor.
  
  
  CONCLUSIONS
  Our results show that serotype O1 strains of V. cholerae do express Hcp which is regarded as one of the important T6SS components and is one of the secreted substrates in non-O1 non-O139 V. cholerae isolates. We found that expression of Hcp was strictly regulated by the quorum sensing system in the V. cholerae O1 strain. In addition, the expression of Hcp required the alternative sigma factor RpoN and the cAMP-CRP global regulatory complex. Interestingly, the environmental isolates of V. cholerae O1 strains that showed higher levels of the HapR quorum sensing regulator in comparison with our laboratory standard serotype O1 strain A1552 where also expressing higher levels of Hcp.
authors.affiliation: Department of Molecular Biology, Umeå University, Umeå, Sweden.
authors.forename: Takahiko
authors.initials: T
authors.lastname: Ishikawa
authors.forename: Pramod Kumar
authors.initials: PK
authors.lastname: Rompikuntal
authors.forename: Barbro
authors.initials: B
authors.lastname: Lindmark
authors.forename: Debra L
authors.initials: DL
authors.lastname: Milton
authors.forename: Sun Nyunt
authors.initials: SN
authors.lastname: Wai
mesh_terms: D000483:Alleles; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics*; D001483:Base Sequence; D017931:DNA Primers; D004269:DNA, Bacterial; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D006460:Hemolysin Proteins / Q000737:chemistry / Q000235:genetics*; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction; D053038:Quorum Sensing; D013045:Species Specificity; D014734:Vibrio cholerae / Q000235:genetics / Q000502:physiology*
chemical_list: D001426:Bacterial Proteins; D017931:DNA Primers; D004269:DNA, Bacterial; C097322:Hcp protein, Vibrio cholerae; D006460:Hemolysin Proteins
references.citation: J Bacteriol. 1999 Nov;181(21):6615-22
references.pmid: 10542161
references.citation: Proteomics. 2007 Oct;7(19):3527-37
references.pmid: 17726675
references.citation: Nucleic Acids Res. 1982 Feb 25;10(4):1345-61
references.pmid: 6280140
references.citation: EMBO J. 1992 Dec;11(13):5121-7
references.pmid: 1464331
references.citation: Microbiology (Reading). 2008 Aug;154(Pt 8):2387-2396
references.pmid: 18667571
references.citation: Infect Immun. 2006 Jun;74(6):3576-86
references.pmid: 16714590
references.citation: Appl Environ Microbiol. 2007 Jun;73(11):3742-6
references.pmid: 17434996
references.citation: Proc Natl Acad Sci U S A. 1979 Sep;76(9):4350-4
references.pmid: 388439
references.citation: PLoS Pathog. 2008 Jun 20;4(6):e1000093
references.pmid: 18566662
references.citation: Biochem Biophys Res Commun. 2002 Jul 26;295(4):922-8
references.pmid: 12127983
references.citation: Cell. 2000 Aug 18;102(4):475-85
references.pmid: 10966109
references.citation: Nat Cell Biol. 2007 Jul;9(7):797-803
references.pmid: 17558395
references.citation: Science. 2006 Jun 9;312(5779):1526-30
references.pmid: 16763151
references.citation: J Bacteriol. 1998 Feb;180(4):773-84
references.pmid: 9473029
references.citation: Nature. 1970 Aug 15;227(5259):680-5
references.pmid: 5432063
references.citation: Proc Natl Acad Sci U S A. 2006 Jun 13;103(24):9280-5
references.pmid: 16754867
references.citation: Mol Plant Microbe Interact. 2003 Jan;16(1):53-64
references.pmid: 12580282
references.citation: FEMS Microbiol Lett. 2000 Sep 1;190(1):87-91
references.pmid: 10981695
references.citation: Mol Microbiol. 2008 Oct;70(1):100-11
references.pmid: 18681937
references.citation: Proc Natl Acad Sci U S A. 2002 Mar 5;99(5):3129-34
references.pmid: 11854465
references.citation: Mol Microbiol. 2007 Feb;63(3):859-71
references.pmid: 17181781
references.citation: Cell. 2004 Jul 9;118(1):69-82
references.pmid: 15242645
references.citation: Microb Pathog. 2008 Apr;44(4):344-61
references.pmid: 18037263
references.citation: Mol Microbiol. 2007 Jun;64(6):1466-85
references.pmid: 17555434
references.citation: Gene. 1996 Feb 22;169(1):47-52
references.pmid: 8635748
references.citation: J Mol Biol. 1983 Jun 5;166(4):557-80
references.pmid: 6345791
references.citation: Proc Natl Acad Sci U S A. 2006 Jan 31;103(5):1528-33
references.pmid: 16432199
references.citation: Proc Natl Acad Sci U S A. 2007 Sep 25;104(39):15508-13
references.pmid: 17873062
references.citation: Science. 2006 Feb 24;311(5764):1113-6
references.pmid: 16497924
references.citation: In Silico Biol. 2003;3(3):287-300
references.pmid: 12954091
references.citation: Infect Immun. 2008 May;76(5):1979-91
references.pmid: 18316384
references.citation: Infect Immun. 1991 Dec;59(12):4310-7
references.pmid: 1937792
references.citation: J Bacteriol. 1988 Jun;170(6):2575-83
references.pmid: 2836362
references.citation: Curr Opin Microbiol. 2008 Feb;11(1):3-8
references.pmid: 18289922
references.citation: Infect Immun. 1996 Jan;64(1):283-9
references.pmid: 8557353
references.citation: Mol Microbiol. 2004 Jul;53(2):573-86
references.pmid: 15228535
references.citation: Infect Immun. 2009 Mar;77(3):935-42
references.pmid: 19103773
references.citation: Microbiology (Reading). 2007 Sep;153(Pt 9):2964-2975
references.pmid: 17768239
references.citation: Cell Host Microbe. 2007 Apr 19;1(2):95-107
references.pmid: 18005688
references.citation: Gene. 1977;2(2):95-113
references.pmid: 344137
references.citation: Mol Microbiol. 2007 Dec;66(5):1192-206
references.pmid: 17986187
references.citation: Infect Immun. 1996 Jul;64(7):2853-6
references.pmid: 8698524
references.citation: Dev Cell. 2004 Nov;7(5):745-54
references.pmid: 15525535