Role of NtrC in biofilm formation via controlling expression of the gene encoding an ADP-glycero-manno-heptose-6-epimerase in the pathogenic bacterium, Vibrio vulnificus.
To identify the genetic elements required for biofilm formation, we screened a pool of random Vibrio vulnificus mutants for their ability to form biofilms. One mutant displaying significantly decreased biofilm-forming activity was found to contain a transposon insertion in the ntrC gene. The ntrC gene encodes a well-known transcriptional activator. We examined how this regulator modulates a biofilm-forming process in V. vulnificus by searching for NtrC target gene(s). Comparison of the proteomes of ntrC mutant and wild-type strains grown under planktonic and biofilm stages revealed that synthesis of the protein homologous to GmhD (ADP-glycero-manno-heptose-6-epimerase) was elevated during the growth period for biofilm formation and was strongly influenced by NtrC. A luxAB-transcriptional fusion with the gmhD promoter region indicated that gmhD expression was positively regulated by both NtrC and RpoN. The function of the gmhD gene product in V. vulnificus was assessed by constructing and phenotypic analyses of an isogenic mutant. The gmhD mutant was defective in production of mature lipopolysaccharide (LPS) and exopolysaccharides (EPS), and demonstrated an attenuated ability to form a biofilm. These results suggest that NtrC acts as a key regulator of both LPS and EPS biosyntheses and, thereby, modulates critical steps in biofilm development of V. vulnificus.
Kim
Han-Suk
HS
Department of Environmental Science, Hankuk University of Foreign Studies, Yongin, Kyunggi-Do 449-791, Korea.
Lee
Mi-Ae
MA
Chun
Se-Jin
SJ
Park
Soon-Jung
SJ
Lee
Kyu-Ho
KH
D019677:Artificial Gene Fusion; D001426:Bacterial Proteins / Q000032:analysis / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology; D018441:Biofilms / Q000254:growth & development*; D002238:Carbohydrate Epimerases / Q000096:biosynthesis*; D004251:DNA Transposable Elements; D015180:Electrophoresis, Gel, Two-Dimensional; D017353:Gene Deletion; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D017930:Genes, Reporter; D008070:Lipopolysaccharides / Q000096:biosynthesis; D008156:Luciferases / Q000032:analysis / Q000235:genetics; D016254:Mutagenesis, Insertional; D011135:Polysaccharides, Bacterial / Q000096:biosynthesis; D020543:Proteome / Q000032:analysis; D051877:RNA Polymerase Sigma 54 / Q000235:genetics / Q000502:physiology; D014157:Transcription Factors / Q000235:genetics / Q000502:physiology*; D041261:Vibrio vulnificus / Q000235:genetics* / Q000502:physiology
D001426:Bacterial Proteins; D004251:DNA Transposable Elements; D008070:Lipopolysaccharides; D011135:Polysaccharides, Bacterial; D020543:Proteome; D014157:Transcription Factors; D008156:Luciferases; D051877:RNA Polymerase Sigma 54; C037213:ADP-L-glycero-D-mannoheptose-6-epimerase; D002238:Carbohydrate Epimerases