A Diverse Repertoire of Exopolysaccharide Biosynthesis Gene Clusters in Lactobacillus Revealed by Comparative Analysis in 106 Sequenced Genomes

Abstract

Production of exopolysaccharides (EPS) is one of the unique features of Lactobacillus genus. EPS not only have many physiological roles such as in stress tolerance, quorum sensing and biofilm formation, but also have numerous applications in the food and pharmaceutical industries. In this study, we identified and compared EPS biosynthesis gene clusters in 106 sequenced Lactobacillus genomes representing 27 species. Of the 146 identified clusters, only 41 showed the typical generic organization of genes as reported earlier. Hierarchical clustering showed highly varied nature of the clusters in terms of the gene composition; nonetheless, habitat-wise grouping was observed for the gene clusters from host-adapted and nomadic strains. Of the core genes required for EPS biosynthesis, epsA, B, C, D and E showed higher conservation, whereas gt, wzx and wzy showed high variability in terms of the number and composition of the protein families. Analysis of the distribution pattern of the protein families indicated a higher proportion of mutually exclusive families in clusters from host-adapted and nomadic strains, whereas those from the free-living group had very few unique families. Taken together, this analysis highlights high variability in the EPS gene clusters amongst Lactobacillus with some of their properties correlated to the habitats.