title: The RNA processing enzyme polynucleotide phosphorylase negatively controls biofilm formation by repressing poly-N-acetylglucosamine (PNAG) production in Escherichia coli C.
abstract: BACKGROUND
  Transition from planktonic cells to biofilm is mediated by production of adhesion factors, such as extracellular polysaccharides (EPS), and modulated by complex regulatory networks that, in addition to controlling production of adhesion factors, redirect bacterial cell metabolism to the biofilm mode.
  
  
  RESULTS
  Deletion of the pnp gene, encoding polynucleotide phosphorylase, an RNA processing enzyme and a component of the RNA degradosome, results in increased biofilm formation in Escherichia coli. This effect is particularly pronounced in the E. coli strain C-1a, in which deletion of the pnp gene leads to strong cell aggregation in liquid medium. Cell aggregation is dependent on the EPS poly-N-acetylglucosamine (PNAG), thus suggesting negative regulation of the PNAG biosynthetic operon pgaABCD by PNPase. Indeed, pgaABCD transcript levels are higher in the pnp mutant. Negative control of pgaABCD expression by PNPase takes place at mRNA stability level and involves the 5'-untranslated region of the pgaABCD transcript, which serves as a cis-element regulating pgaABCD transcript stability and translatability.
  
  
  CONCLUSIONS
  Our results demonstrate that PNPase is necessary to maintain bacterial cells in the planktonic mode through down-regulation of pgaABCD expression and PNAG production.
authors.affiliation: Department of Biosciences, University of Milan, Via Celoria 26, Milan, 20133, Italy.
authors.forename: Thomas
authors.initials: T
authors.lastname: Carzaniga
authors.forename: Davide
authors.initials: D
authors.lastname: Antoniani
authors.forename: Gianni
authors.initials: G
authors.lastname: Dehò
authors.forename: Federica
authors.initials: F
authors.lastname: Briani
authors.forename: Paolo
authors.initials: P
authors.lastname: Landini
mesh_terms: D000117:Acetylglucosamine / Q000378:metabolism*; D018441:Biofilms / Q000254:growth & development*; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D017353:Gene Deletion; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial; D011117:Polyribonucleotide Nucleotidyltransferase / Q000235:genetics / Q000378:metabolism*; D020871:RNA Stability; D012329:RNA, Bacterial / Q000378:metabolism*
chemical_list: D012329:RNA, Bacterial; C113831:poly-N-acetyl glucosamine; D011117:Polyribonucleotide Nucleotidyltransferase; D000117:Acetylglucosamine