Isolation of an efficient glycosaminoglycans degrading human gut Firmicutes Hungatella hathewayi and the characterization of its Chondroitin ABC exolyase with high activity and broad substrate specificity

The degradation of glycosaminoglycans (GAGs) by intestinal bacteria is critical for their colonization in the human gut and the health of the host. Both Bacteroides and Firmicutes have been reported to degrade GAGs, while the enzymatic details of the latter remain largely unknown. In this study, we isolated a Firmicutes strain, Hungatella hathewayi N2-326, that can catabolize various GAGs. While H. hathewayi N2-326 was less efficient in utilizing chondroitin sulfate A (CSA) and dermatan sulfate (DS) than Bacteroides thetaiotaomicron, a characterized GAG degrader, it outperformed B. thetaiotaomicron in assimilating hyaluronic acid. Unlike B. thetaiotaomicron, H. hathewayi N2-326 could not utilize heparin. The chondroitin lyase activity of H. hathewayi N2-326 was found to be induced by CSA and displayed both cell-associated and extracellular distributions. We further identified and characterized the first chondroitin ABC lyase from Firmicutes. The recombinant H. hathewayi chondroitin ABC lyase was found to be a predominantly exolyase and exhibited higher specific activity than any other characterized chondroitin ABC lyase. Thus, the HH-chondroitin ABC lyase offers a viable commercial option for the production of chondroitin, dermatan, and hyaluronan oligosaccharides and potential medical applications. Comparative gene expression analysis of RNA-seq data for Hungatella hathewayi N2-326 cells grown to mid-log phase on either 1.5% chondroitin sulfate A (CSA) or 1.5% glucose (Glc). Three replicates for each group, i.e. CSA and glc, were included.