title: Gene expression regulation by the Curli activator CsgD protein: modulation of cellulose biosynthesis and control of negative determinants for microbial adhesion.
abstract: Curli fibers, encoded by the csgBAC genes, promote biofilm formation in Escherichia coli and other enterobacteria. Curli production is dependent on the CsgD transcription activator, which also promotes cellulose biosynthesis. In this study, we investigated the effects of CsgD expression from a weak constitutive promoter in the biofilm formation-deficient PHL565 strain of E. coli. We found that despite its function as a transcription activator, the CsgD protein is localized in the cytoplasmic membrane. Constitutive CsgD expression promotes biofilm formation by PHL565 and activates transcription from the csgBAC promoter; however, csgBAC expression remains dependent on temperature and the growth medium. Constitutive expression of the CsgD protein results in altered transcription patterns for at least 24 novel genes, in addition to the previously identified CsgD-dependent genes. The cspA and fecR genes, encoding regulatory proteins responding to cold shock and to iron, respectively, and yoaD, encoding a putative negative regulator of cellulose biosynthesis, were found to be some of the novel CsgD-regulated genes. Consistent with the predicted functional role, increased expression of the yoaD gene negatively affects cell aggregation, while yoaD inactivation results in stimulation of cell aggregation and leads to increased cellulose production. Inactivation of fecR results in significant increases in both cell aggregation and biofilm formation, while the effects of cspA are not as strong in the conditions tested. Our results indicate that CsgD can modulate cellulose biosynthesis through activation of the yoaD gene. In addition, the positive effect of CsgD on biofilm formation might be enhanced by repression of the fecR gene.
authors.affiliation: Swiss Federal Institute of Environmental Technology, Dübendorf, Switzerland.
authors.forename: Eva
authors.initials: E
authors.lastname: Brombacher
authors.forename: Andrea
authors.initials: A
authors.lastname: Baratto
authors.forename: Corinne
authors.initials: C
authors.lastname: Dorel
authors.forename: Paolo
authors.initials: P
authors.lastname: Landini
mesh_terms: D019677:Artificial Gene Fusion; D001422:Bacterial Adhesion / Q000235:genetics / Q000502:physiology*; D018441:Biofilms / Q000254:growth & development; D002462:Cell Membrane / Q000737:chemistry; D002482:Cellulose / Q000096:biosynthesis*; D057773:Cold Shock Proteins and Peptides; D003470:Culture Media / Q000737:chemistry; D004926:Escherichia coli / Q000235:genetics / Q000502:physiology*; D029968:Escherichia coli Proteins / Q000032:analysis / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D017353:Gene Deletion; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology*; D017930:Genes, Reporter; D005966:Glucuronidase / Q000032:analysis / Q000235:genetics; D006360:Heat-Shock Proteins / Q000235:genetics; D026901:Membrane Transport Proteins / Q000235:genetics; D008954:Models, Biological; D010727:Phosphoric Diester Hydrolases / Q000235:genetics; D011401:Promoter Regions, Genetic; D012808:Sigma Factor / Q000235:genetics; D013696:Temperature; D015534:Trans-Activators / Q000032:analysis / Q000502:physiology*; D014158:Transcription, Genetic
chemical_list: D057773:Cold Shock Proteins and Peptides; C109182:CsgB protein, E coli; C499694:CsgD protein, E coli; C498192:CspA protein, E coli; D003470:Culture Media; D029968:Escherichia coli Proteins; C093541:FecR protein, E coli; D006360:Heat-Shock Proteins; D026901:Membrane Transport Proteins; D012808:Sigma Factor; D015534:Trans-Activators; C489688:csgA protein, E coli; D002482:Cellulose; D010727:Phosphoric Diester Hydrolases; D005966:Glucuronidase