Bioprospecting c-di-GMP activated exopolysaccharides in bacteria

Abstract

The genetic and physiological diversity of bacteria are critical resources to discover new exopolysaccharides (EPS) as raw materials with biotechnological applications. However, uncovering new EPS is limited by their lack of production in laboratory cultures, as EPS are often cryptic and their biosynthesis only proceed upon unknown environmental cues. The dinucleotide cyclic di-GMP (c-di-GMP) has emerged as a universal second messenger in bacteria and common activator of many EPS. Here, a genetic modification to elevate intracellular c-di-GMP levels and a carbohydrate fingerprinting analysis, were combined for a High-Throughput Screening (HTS) of 330 bacterial strains in search of c-di-GMP activated EPS. Nearly 10% of strains were revealed as promising candidates to overproduce novel EPS composites, in a c-di-GMP dependent manner. In these conditions, Sphingomonas sp. C10 massively produced a EPS with an unusual monosaccharide composition, compared to known biotechnologically relevant sphingans.