title: Mutants of Streptococcus gordonii Challis over-producing glucosyltransferase.
abstract: Two mutants of Streptococcus gordonii which over-produced extracellular polysaccharide when grown on sucrose-containing medium were isolated after mutagenesis of strain Challis with ethyl methanesulphonate. The mutants, designated strains OB20 and OB30, expressed 2.6-fold and 4.7-fold respectively more glucosyltransferase (GTF) activities than the wild-type strain. Transformation experiments suggested that the two mutants carried different mutations, denoted gtf-20 and gtf-30. A double mutant (gtf-20 gtf-30) was constructed and this strain produced 6.4-fold more GTF. Enzymes from wild-type and mutant strains were biochemically indistinguishable and they synthesized structurally identical glucans. Increasing the Na+ concentration of the bacterial growth medium reduced GTF production in all strains by about 60%. Tween 80 also inhibited enzyme production and more specifically reduced GTF synthesis by the mutants. The mutations gtf-20 and gtf-30 appear to define separate genetic loci involved in regulating expression of GTF activity in S. gordonii.
authors.affiliation: Department of Oral Biology and Oral Pathology, University of Otago, Dunedin, New Zealand.
authors.forename: R J
authors.initials: RJ
authors.lastname: Haisman
authors.forename: H F
authors.initials: HF
authors.lastname: Jenkinson
mesh_terms: D004591:Electrophoresis, Polyacrylamide Gel; D005020:Ethyl Methanesulfonate / Q000494:pharmacology; D015964:Gene Expression Regulation, Bacterial; D005936:Glucans / Q000378:metabolism; D005964:Glucosyltransferases / Q000096:biosynthesis / Q000235:genetics*; D009682:Magnetic Resonance Spectroscopy; D016296:Mutagenesis; D009154:Mutation; D010504:Periodic Acid / Q000378:metabolism; D012964:Sodium / Q000494:pharmacology; D013291:Streptococcus / Q000201:enzymology / Q000235:genetics* / Q000302:isolation & purification; D014169:Transformation, Bacterial
chemical_list: D005936:Glucans; D010504:Periodic Acid; D005020:Ethyl Methanesulfonate; D012964:Sodium; C009288:metaperiodate; C036655:1,3-alpha-D-glucan synthase; D005964:Glucosyltransferases