title: Evidence for a role for the gumB and gumC gene products in the formation of xanthan from its pentasaccharide repeating unit by Xanthomonas campestris.
abstract: The biosynthesis of the extracellular polysaccharide xanthan in Xanthomonas campestris pv. campestris is directed by a cluster of 12 genes, gumB-gumM. Several xanthan-deficient mutants of the wild-type strain 8004 have previously been described which carry Tn5 insertions in this region of the chromosome. Here it is shown that the transposon insertion in one of these mutants, strain 8397, is located 15 bp upstream of the translational start site of the gumB gene. EDTA-treated cells of strain 8397 were able to synthesize the lipid-linked pentasaccharide repeating unit of xanthan from the three nucleotide sugar donors (UDP-glucose, GDP-mannose and UDP-glucuronic acid) but were unable to polymerize the pentasaccharide into mature xanthan. A subclone of the gum gene cluster carrying gumB and gumC restored xanthan production to strain 8397 to levels approximately 28% of the wild-type. In contrast, subclones carrying gumB or gumC alone were not effective. These results are discussed with reference to previous speculations, based on computer analysis, that gumB and gumC are both involved in the translocation of xanthan across the bacterial membranes.
authors.affiliation: Instituto de Investigaciones Bioquímicas Fundación Campomar, Facultad de Ciencias Exactas y Naturales and Consejo Nacional de Investigaciones Cientificas y Técnicas, Av. Patricias Argentinas 435, 1405 Buenos Aires, Argentina.
authors.forename: Adrián A
authors.initials: AA
authors.lastname: Vojnov
authors.affiliation: Instituto de Investigaciones Bioquímicas Fundación Campomar, Facultad de Ciencias Exactas y Naturales and Consejo Nacional de Investigaciones Cientificas y Técnicas, Av. Patricias Argentinas 435, 1405 Buenos Aires, Argentina.
authors.forename: Angeles
authors.initials: A
authors.lastname: Zorreguieta
authors.affiliation: The Sainsbury Laboratory, John Innes Centre, Norwich Research Park, Colney Lane, Norwich NR4 7UH, UK.
authors.forename: J Maxwell
authors.initials: JM
authors.lastname: Dow
authors.affiliation: The Sainsbury Laboratory, John Innes Centre, Norwich Research Park, Colney Lane, Norwich NR4 7UH, UK.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Daniels
authors.affiliation: Instituto de Investigaciones Bioquímicas Fundación Campomar, Facultad de Ciencias Exactas y Naturales and Consejo Nacional de Investigaciones Cientificas y Técnicas, Av. Patricias Argentinas 435, 1405 Buenos Aires, Argentina.
authors.forename: Marcelo A
authors.initials: MA
authors.lastname: Dankert
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism*; D002848:Chromatography, DEAE-Cellulose; D002852:Chromatography, Ion Exchange; D004251:DNA Transposable Elements; D005798:Genes, Bacterial / Q000502:physiology*; D006155:Guanosine Diphosphate Mannose / Q000378:metabolism; D016133:Polymerase Chain Reaction; D011135:Polysaccharides, Bacterial / Q000378:metabolism*; D011854:Radiochemistry; D014532:Uridine Diphosphate Glucose / Q000378:metabolism; D014535:Uridine Diphosphate Glucuronic Acid / Q000378:metabolism; D016959:Xanthomonas campestris / Q000201:enzymology* / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D004251:DNA Transposable Elements; D011135:Polysaccharides, Bacterial; D014535:Uridine Diphosphate Glucuronic Acid; D006155:Guanosine Diphosphate Mannose; D014532:Uridine Diphosphate Glucose