title: EpsA is an essential gene in exopolysaccharide production in Lactobacillus johnsonii FI9785.
abstract: Lactobacillus johnsonii FI9785 has an eps gene cluster which is required for the biosynthesis of homopolymeric exopolysaccharides (EPS)-1 and heteropolymeric EPS-2 as a capsular layer. The first gene of the cluster, epsA, is the putative transcriptional regulator. In this study we showed the crucial role of epsA in EPS biosynthesis by demonstrating that deletion of epsA resulted in complete loss of both EPS-1 and EPS-2 on the cell surface. Plasmid complementation of the epsA gene fully restored EPS production, as confirmed by transmission electron microscopy and nuclear magnetic resonance (NMR) analysis. Furthermore, this complementation resulted in a twofold increase in the expression levels of this gene, which almost doubled amounts of EPS production in comparison with the wild-type strain. Analysis of EPS by NMR showed an increased ratio of the heteropolysaccharide to homopolysaccharide in the complemented strain and allowed identification of the acetylated residue in EPS-2 as the (1,4)-linked βGlcp unit, with the acetyl group located at O-6. These findings indicate that epsA is a positive regulator of EPS production and that EPS production can be manipulated by altering its expression.
authors.affiliation: Department of Gut Health and Food Safety, Institute of Food Research, Norwich, Colney, NR4 7UA, UK.|Department of Food Engineering, Faculty of Engineering, Bayburt University, Bayburt, 69000, Turkey.
authors.forename: Enes
authors.initials: E
authors.lastname: Dertli
authors.affiliation: Department of Gut Health and Food Safety, Institute of Food Research, Norwich, Colney, NR4 7UA, UK.
authors.forename: Melinda J
authors.initials: MJ
authors.lastname: Mayer
authors.affiliation: Analytical Sciences Unit, Institute of Food Research, Norwich, Colney, NR4 7UA, UK.
authors.forename: Ian J
authors.initials: IJ
authors.lastname: Colquhoun
authors.affiliation: Department of Gut Health and Food Safety, Institute of Food Research, Norwich, Colney, NR4 7UA, UK.
authors.forename: Arjan
authors.initials: A
authors.lastname: Narbad
mesh_terms: D017353:Gene Deletion; D005798:Genes, Bacterial; D020043:Genes, Essential; D005816:Genetic Complementation Test; D000069999:Lactobacillus johnsonii / Q000235:genetics* / Q000378:metabolism* / Q000648:ultrastructure; D009682:Magnetic Resonance Spectroscopy; D046529:Microscopy, Electron, Transmission; D005810:Multigene Family; D011135:Polysaccharides, Bacterial / Q000096:biosynthesis*
chemical_list: D011135:Polysaccharides, Bacterial