title: Inhibition of SypG-induced biofilms and host colonization by the negative regulator SypE in Vibrio fischeri.
abstract: Vibrio fischeri produces a specific biofilm to promote colonization of its eukaryotic host, the squid Euprymna scolopes. Formation of this biofilm is induced by the sensor kinase RscS, which functions upstream of the response regulator SypG to regulate transcription of the symbiosis polysaccharide (syp) locus. Biofilm formation is also controlled by SypE, a multi-domain response regulator that consists of a central regulatory receiver (REC) domain flanked by an N-terminal serine kinase domain and a C-terminal serine phosphatase domain. SypE permits biofilm formation under rscS overexpression conditions, but inhibits biofilms induced by overexpression of sypG. We previously investigated the function of SypE in controlling biofilm formation induced by RscS. Here, we examined the molecular mechanism by which SypE naturally inhibits SypG-induced biofilms. We found that SypE's N-terminal kinase domain was both required and sufficient to inhibit SypG-induced biofilms. This effect did not occur at the level of syp transcription. Instead, under sypG-overexpressing conditions, SypE inhibited biofilms by promoting the phosphorylation of another syp regulator, SypA, a putative anti-sigma factor antagonist. Inhibition by SypE of SypG-induced biofilm formation could be overcome by the expression of a non-phosphorylatable SypA mutant, indicating that SypE functions primarily if not exclusively to control SypA activity via phosphorylation. Finally, the presence of SypE was detrimental to colonization under sypG-overexpressing conditions, as cells deleted for sypE outcompeted wild-type cells for colonization when both strains overexpressed sypG. These results provide further evidence that biofilm formation is critical to symbiotic colonization, and support a model in which SypE naturally functions to restrict biofilm formation, and thus host colonization, to the appropriate environmental conditions.
authors.affiliation: Department of Microbiology and Immunology, Loyola University Medical Center, Maywood, IL, USA.
authors.forename: Andrew R
authors.initials: AR
authors.lastname: Morris
authors.forename: Karen L
authors.initials: KL
authors.lastname: Visick
mesh_terms: D048908:Aliivibrio fischeri / Q000235:genetics / Q000378:metabolism* / Q000502:physiology*; D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D018441:Biofilms / Q000254:growth & development*; D049832:Decapodiformes / Q000382:microbiology*; D015964:Gene Expression Regulation, Bacterial / Q000235:genetics / Q000502:physiology
chemical_list: D001426:Bacterial Proteins
references.citation: Proc Natl Acad Sci U S A. 2000 Aug 29;97(18):10231-5
references.pmid: 10963683
references.citation: Mol Microbiol. 2004 Aug;53(4):1123-34
references.pmid: 15306016
references.citation: J Bacteriol. 1990 Jul;172(7):3701-6
references.pmid: 2163384
references.citation: Mol Cell Proteomics. 2006 Apr;5(4):749-57
references.pmid: 16340016
references.citation: Nat Rev Microbiol. 2004 Aug;2(8):632-42
references.pmid: 15263898
references.citation: J Bacteriol. 2006 May;188(10):3600-13
references.pmid: 16672614
references.citation: J Bacteriol. 2007 Aug;189(16):5825-38
references.pmid: 17586650
references.citation: Mol Cell Proteomics. 2007 Feb;6(2):356-66
references.pmid: 17088264
references.citation: Appl Environ Microbiol. 2006 Jan;72(1):802-10
references.pmid: 16391121
references.citation: J Vis Exp. 2012 Jun 07;(64):e4035
references.pmid: 22710417
references.citation: Curr Opin Microbiol. 2006 Dec;9(6):632-8
references.pmid: 17049299
references.citation: Curr Opin Biotechnol. 2000 Oct;11(5):429-33
references.pmid: 11024358
references.citation: Environ Microbiol. 2007 Feb;9(2):370-82
references.pmid: 17222135
references.citation: Mol Microbiol. 2005 Sep;57(5):1485-98
references.pmid: 16102015
references.citation: J Bacteriol. 1994 Nov;176(22):6986-91
references.pmid: 7961462
references.citation: J Bacteriol. 2008 Jul;190(13):4576-83
references.pmid: 18441059
references.citation: J Bacteriol. 2005 Aug;187(16):5665-76
references.pmid: 16077112
references.citation: Nat Rev Microbiol. 2004 Feb;2(2):95-108
references.pmid: 15040259
references.citation: Nat Rev Microbiol. 2008 Oct;6(10):752-62
references.pmid: 18794913
references.citation: Mol Microbiol. 2006 Dec;62(6):1586-600
references.pmid: 17087775
references.citation: J Bacteriol. 2001 Feb;183(3):835-42
references.pmid: 11208780
references.citation: Mol Microbiol. 2011 Oct;82(1):114-30
references.pmid: 21854462
references.citation: Mol Microbiol. 2012 Nov;86(4):954-70
references.pmid: 23035866
references.citation: Environ Microbiol. 2010 Aug;12(8):2051-9
references.pmid: 21966901
references.citation: Microbiol Mol Biol Rev. 2009 Jun;73(2):310-47
references.pmid: 19487730
references.citation: Curr Opin Microbiol. 2002 Oct;5(5):472-7
references.pmid: 12354553
references.citation: Mol Microbiol. 2013 Feb;87(3):509-25
references.pmid: 23171087
references.citation: Genes Dev. 1996 Sep 15;10(18):2265-75
references.pmid: 8824586
references.citation: Trends Biochem Sci. 2000 Jan;25(1):24-8
references.pmid: 10637609
references.citation: J Bacteriol. 2012 Dec;194(24):6736-47
references.pmid: 23042998
references.citation: J Biol Chem. 1951 Nov;193(1):265-75
references.pmid: 14907713
references.citation: Methods Enzymol. 2002;358:413-26
references.pmid: 12474404
references.citation: J Bacteriol. 2009 Aug;191(16):5147-58
references.pmid: 19525342
references.citation: Appl Environ Microbiol. 2003 Oct;69(10):5928-34
references.pmid: 14532046