Selective Utilization of Polyguluronate by the Human Gut Bacteroides Species

Human gut <i>Bacteroides</i> species play crucial roles in the metabolism of dietary polysaccharides. Polyguluronate (PG), a major component of alginate, has been widely used in the food and medical industries. However, how PG is utilized by human gut <i>Bacteroides</i> species has not been fully elucidated. Here, using a combination of culturomics, genomics, and state-of-the-art analytical techniques, we elucidated in detail the utilization profiles of PG by 17 different human gut <i>Bacteroides</i> species. Our results indicated that each <i>Bacteroides</i> species exhibited a unique capability for PG utilization. Among all species tested, <i>Bacteroides xylanisolvens</i> consumed the highest amount of PG and produced the greatest quantity of short-chain fatty acids, suggesting that it may be a keystone bacterium in PG utilization. Mass spectrometry showed that PG was degraded by <i>B. xylanisolvens</i> into a series of oligosaccharides. Genomic analyses confirmed that <i>B. xylanisolvens</i> possesses a large and divergent repertoire of carbohydrate-active enzymes. Moreover, genomic annotation identified two enzymes, PL17_2 and PL6_1, in <i>B. xylanisolvens</i> that are potentially responsible for PG degradation. Altogether, our study provides novel insights into PG utilization by human gut <i>Bacteroides</i> species, which has important implications for the development of carbohydrate-based drugs from marine resources.