Identification of genes required for glucan exopolysaccharide production in Lactobacillus johnsonii suggests a novel mechanism of biosynthesis.

Identification of genes required for glucan exopolysaccharide production in Lactobacillus johnsonii suggests a novel mechanism of biosynthesis. Appl Environ Microbiol. 2020 Feb 14;: Authors: Mayer MJ, D'Amato A, Colquhoun IJ, Le Gall G, Narbad A Abstract Lactobacillus johnsonii FI9785 makes two capsular exopolysaccharides -a heteropolysaccharide (EPS2) encoded by the eps operon, and a branched glucan homopolysaccharide (EPS1). The homopolysaccharide is synthesised in the absence of sucrose and there are no typical glucansucrase genes in the genome. Quantitative proteomics was used to compare the wild type to a mutant where EPS production was reduced, to attempt to identify proteins associated with EPS1 biosynthesis. A putative bactoprenol glycosyltransferase, 242, was less abundant in the Δeps_cluster mutant than in the wild type. NMR analysis of isolated EPS showed that deletion of the 242 gene prevented the accumulation of EPS1, without affecting EPS2 synthesis, while plasmid complementation restored EPS1 production. The deletion of 242 also produced a slow growth phenotype, which could be rescued by complementation. 242 shows amino acid homology to bactoprenol glycosyltransferase GtrB, involved in O-antigen glycosylation, while in silico analysis of neighbouring gene 241 suggested it encodes a putative flippase with homology to the GtrA superfamily. Deletion of 241 also prevented production of EPS1, and again caused a slow growth...
Source: Applied and Environmental Microbiology - Category: Microbiology Authors: Tags: Appl Environ Microbiol Source Type: research