title: BcsZ inhibits biofilm phenotypes and promotes virulence by blocking cellulose production in Salmonella enterica serovar Typhimurium.
abstract: BACKGROUND
  Cellulose, a 1,4 beta-glucan polysaccharide, is produced by a variety of organisms including bacteria. Although the production of cellulose has a high biological, ecological and economical impact, regulatory mechanisms of cellulose biosynthesis are mostly unknown. Family eight cellulases are regularly associated with cellulose biosynthesis operons in bacteria; however, their function is poorly characterized. In this study, we analysed the role of the cellulase BcsZ encoded by the bcsABZC cellulose biosynthesis operon of Salmonella enterica serovar Typhimurium (S. Typhimurium) in biofilm related behavior. We also investigated the involvement of BcsZ in pathogenesis of S. Typhimurium including a murine typhoid fever infection model.
  
  
  RESULTS
  In S. Typhimurium, cellulase BcsZ with a putative periplasmic location negatively regulates cellulose biosynthesis. Moreover, as assessed with a non-polar mutant, BcsZ affects cellulose-associated phenotypes such as the rdar biofilm morphotype, cell clumping, biofilm formation, pellicle formation and flagella-dependent motility. Strikingly, although upregulation of cellulose biosynthesis was not observed on agar plate medium at 37 °C, BcsZ is required for efficient pathogen-host interaction. Key virulence phenotypes of S. Typhimurium such as invasion of epithelial cells and proliferation in macrophages were positively regulated by BcsZ. Further on, a bcsZ mutant was outcompeted by the wild type in organ colonization in the murine typhoid fever infection model. Selected phenotypes were relieved upon deletion of the cellulose synthase BcsA and/or the central biofilm activator CsgD.
  
  
  CONCLUSIONS
  Although the protein scaffold has an additional physiological role, our findings indicate that the catalytic activity of BcsZ effectively downregulates CsgD activated cellulose biosynthesis. Repression of cellulose production by BcsZ subsequently enables Salmonella to efficiently colonize the host.
authors.affiliation: Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, Stockholm, Sweden.|Department of Molecular Biology, Umeå University, Umeå, Sweden.
authors.forename: Irfan
authors.initials: I
authors.lastname: Ahmad
authors.affiliation: Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, Stockholm, Sweden.|Département de Biologie, Faculté des Sciences, Université de Sherbrooke, Quebec, Canada.
authors.forename: Syed Fazle
authors.initials: SF
authors.lastname: Rouf
authors.affiliation: Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Lei
authors.initials: L
authors.lastname: Sun
authors.affiliation: Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Annika
authors.initials: A
authors.lastname: Cimdins
authors.affiliation: Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Sulman
authors.initials: S
authors.lastname: Shafeeq
authors.affiliation: Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Soazig
authors.initials: S
authors.lastname: Le Guyon
authors.affiliation: Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Marco
authors.initials: M
authors.lastname: Schottkowski
authors.affiliation: Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Mikael
authors.initials: M
authors.lastname: Rhen
authors.affiliation: Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, Stockholm, Sweden. Ute.Romling@ki.se.
authors.forename: Ute
authors.identifier: http://orcid.org/0000-0003-3776-5018
authors.initials: U
authors.lastname: Römling
mesh_terms: D018441:Biofilms; D002482:Cellulose / Q000037:antagonists & inhibitors / Q000096:biosynthesis*; D005964:Glucosyltransferases / Q000378:metabolism*; D010641:Phenotype; D012486:Salmonella typhimurium / Q000201:enzymology / Q000235:genetics / Q000378:metabolism / Q000502:physiology*
chemical_list: D002482:Cellulose; D005964:Glucosyltransferases; C478648:cellulose synthase
keywords: BcsZ; Biofilm; Cellulase; Cellulose; CsgD; Salmonella