title: Expression of cellulosome components and type IV pili within the extracellular proteome of Ruminococcus flavefaciens 007.
abstract: BACKGROUND
  Ruminococcus flavefaciens is an important fibre-degrading bacterium found in the mammalian gut. Cellulolytic strains from the bovine rumen have been shown to produce complex cellulosome structures that are associated with the cell surface. R. flavefaciens 007 is a highly cellulolytic strain whose ability to degrade dewaxed cotton, but not Avicel cellulose, was lost following initial isolation in the variant 007S. The ability was recovered after serial subculture to give the cotton-degrading strain 007C. This has allowed us to investigate the factors required for degradation of this particularly recalcitrant form of cellulose.
  
  
  RESULTS
  The major proteins associated with the bacterial cell surface and with the culture supernatant were analyzed for R. flavefaciens 007S and 007C grown with cellobiose, xylan or Avicel cellulose as energy sources. Identification of the proteins was enabled by a draft genome sequence obtained for 007C. Among supernatant proteins a cellulosomal GH48 hydrolase, a rubrerthyrin-like protein and a protein with type IV pili N-terminal domain were the most strongly up-regulated in 007C cultures grown on Avicel compared with cellobiose. Strain 007S also showed substrate-related changes, but supernatant expression of the Pil protein and rubrerythrin in particular were markedly lower in 007S than in 007C during growth on Avicel.
  
  
  CONCLUSIONS
  This study provides new information on the extracellular proteome of R. flavefaciens and its regulation in response to different growth substrates. Furthermore it suggests that the cotton cellulose non-degrading strain (007S) has altered regulation of multiple proteins that may be required for breakdown of cotton cellulose. One of these, the type IV pilus was previously shown to play a role in adhesion to cellulose in R. albus, and a related pilin protein was identified here for the first time as a major extracellular protein in R. flavefaciens.
authors.affiliation: Chair for Microbiology and Microbial Biotechnology, Biotechnical Faculty, University of Ljubljana, Ljubljana, Slovenia.
authors.forename: Maša
authors.initials: M
authors.lastname: Vodovnik
authors.forename: Sylvia H
authors.initials: SH
authors.lastname: Duncan
authors.forename: Martin D
authors.initials: MD
authors.lastname: Reid
authors.forename: Louise
authors.initials: L
authors.lastname: Cantlay
authors.forename: Keith
authors.initials: K
authors.lastname: Turner
authors.forename: Julian
authors.initials: J
authors.lastname: Parkhill
authors.forename: Raphael
authors.initials: R
authors.lastname: Lamed
authors.forename: Carl J
authors.initials: CJ
authors.lastname: Yeoman
authors.forename: Margret E Berg
authors.initials: ME
authors.lastname: Miller
authors.forename: Bryan A
authors.initials: BA
authors.lastname: White
authors.forename: Edward A
authors.initials: EA
authors.lastname: Bayer
authors.forename: Romana
authors.initials: R
authors.lastname: Marinšek-Logar
authors.forename: Harry J
authors.initials: HJ
authors.lastname: Flint
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D002482:Cellulose / Q000378:metabolism; D044603:Cellulosomes / Q000378:metabolism*; D005110:Extracellular Space / Q000378:metabolism*; D010861:Fimbriae, Bacterial / Q000235:genetics / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D006422:Hemerythrin / Q000378:metabolism; D005810:Multigene Family; D020543:Proteome / Q000235:genetics / Q000378:metabolism*; D012416:Rubredoxins / Q000378:metabolism; D045857:Ruminococcus / Q000166:cytology* / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D006422:Hemerythrin; D020543:Proteome; D012416:Rubredoxins; C055857:rubrerythrins; D002482:Cellulose