The genome of the soil Bacteroidota Chitinophaga pinensis encodes a large number of glycoside hydrolases (GHs) with noteworthy features and potentially novel functions. Several are predicted to be active on polysaccharide components of fungal and oomycete cell walls, such as chitin, β‐1,3‐glucan and β‐1,6‐glucan. While several fungal β‐1,6‐glucanase enzymes are known, relatively few bacterial examples have been characterised to date. We have previously demonstrated that C. pinensis shows strong growth using β‐1,6‐glucan as the sole carbon source, with the efficient release of oligosaccharides from the polymer. We here characterise the capacity of the C. pinensis secretome to hydrolyse the β‐1,6‐glucan pustulan and describe three distinct enzymes encoded by its genome, all of which show different levels of β‐1,6‐glucanase activity and which are classified into different GH families. Our data show that C. pinensis has multiple tools to deconstruct pustulan, allowing the species' broad utility of this substrate, with potential implications for bacterial biocontrol of pathogens via cell wall disruption. Oligosaccharides derived from fungal β‐1,6‐glucans are valuable in biomedical research and drug synthesis, and these enzymes could be useful tools for releasing such molecules from microbial biomass, an underexploited source of complex carbohydrates.

The secretion of extracellular enzymes by soil microbes is rate-limiting in the global recycling of biomass. Fungi and bacteria compete and collaborate for nutrients in the soil, with wide ranging ecological impacts. Within soil microbiota, the Bacteroidetes tend to be a dominant bacterial phylum, just like in human and animal intestines. The enzymology of Bacteroidetes in the dynamic and competitive soil environment is under-explored compared to their cousins from the human and ruminant gut ecosystems. We are exploring carbohydrate binding and deconstruction by Chitinophaga pinensis. This species was isolated from the leaf litter of a pine forest, and our ongoing microbiological, biochemical, and proteomic analyses show that C. pinensis has a marked metabolic preference for carbohydrates (glycans) of microbial, rather than plant, origin. The species has a repertoire of enzymes that degrade components of the fungal cell wall, and we are characterising several important enzyme activities, including some with unusual substrate specificity. Several features of the C. pinensis “cazome” make it note-worthy. In particular, there is a significantly reduced reliance on the Polysaccharide Utilisation Loci that define glycan acquisition in most well-studied gut symbiont Bacteroidetes. Instead, C. pinensis produces some large multi-modular enzymes that convey multiple complementary carbohydrate-binding and -degrading functions, and which are often secreted via the phylum-specific Type IX Secretion System. This presentation will highlight our latest enzyme characterisation data, discussed in the context of the environmental functions of soil bacteria, as well as the use of enzymes for industrial biotechnology.