Facimoto Cesar T, Clements Kendall D, White W Lindsey, Handley Kim M
School of Biological Sciences, The University of Auckland, Auckland, New Zealand.
Department of Environmental Science, Auckland University of Technology, Auckland, New Zealand.
mSystems. 2025 Jan 21;10(1):e0100724. doi: 10.1128/msystems.01007-24. Epub 2024 Dec 23.
The genus () is most often associated with human clinical samples and livestock. However, are also prevalent in the hindgut of the marine herbivorous fish (Silver Drummer), and analysis of their carbohydrate-active enzyme (CAZyme) encoding gene repertoires suggests degrade macroalgal biomass to support fish nutrition. To further explore host-associated traits unique to -derived , we compared 445 high-quality genomes of available in public databases (e.g., human and ruminant associated) with 99 metagenome-assembled genomes (MAGs) from the gut. Analyses showed that from are phylogenetically distinct from other hosts and comprise 26 species based on genomic average nucleotide identity (ANI) analyses. Ruminant- and fish-derived had significantly smaller genomes than human-derived strains, and lower GC contents, possibly reflecting a symbiotic relationship with their hosts. The fish-derived were further delineated by their genetic capacity to fix nitrogen, biosynthesize cobalamin (vitamin B12), and utilize marine polysaccharides (e.g., alginate and carrageenan). The distribution of CAZymes encoded by from was not phylogenetically conserved. Distinct CAZyme gene compositions were observed between closely related species. Conversely, CAZyme gene clusters (operons) targeting the same substrates were found across diverse species. Nonetheless, transcriptional data suggest that closely related target specific groups of substrates within the fish hindgut. Results highlight host-specific adaptations among in the fish hindgut that likely contribute to digesting their seaweed diet, and diverse and redundant carbohydrate-degrading capabilities across these species.IMPORTANCEDespite numerous reports of the genus in humans and ruminants, its diversity and function remain understudied, and there is no clear consensus on whether it positively or negatively impacts host health. Given the symbiotic role of gut communities in the hindgut, where are prevalent, and the diversity of carbohydrate-active enzymes (CAZymes) encoded that likely contribute to the breakdown of important substrates in the host diet, it is likely that this genus provides essential services to the fish host. Therefore, considering its metabolism in various contexts and hosts is crucial for understanding the ecology of the genus. Our study highlights the distinct genetic traits of based on host association, and the potential of fish-associated to transform macroalgae biomass into nutraceuticals (alginate oligosaccharides, β-glucans, sulfated galactans, and sulfated fucans).
某属（此处原文缺失属名）最常与人类临床样本和家畜相关联。然而，该属在海洋草食性鱼类（银鼓鱼）的后肠中也很普遍，对其编码碳水化合物活性酶（CAZyme）的基因库进行分析表明，该属可降解大型藻类生物质以支持鱼类营养。为了进一步探索源自该属且与宿主相关的独特特征，我们将公共数据库中可用的445个高质量该属基因组（例如与人类和反刍动物相关的）与来自银鼓鱼肠道的99个宏基因组组装基因组（MAGs）进行了比较。分析表明，源自银鼓鱼的该属在系统发育上与其他宿主不同，基于基因组平均核苷酸同一性（ANI）分析，其包含26个物种。源自反刍动物和鱼类的该属基因组明显小于源自人类的菌株，且GC含量较低，这可能反映了它们与宿主的共生关系。源自鱼类的该属还通过其固氮、生物合成钴胺素（维生素B12）以及利用海洋多糖（如藻酸盐和卡拉胶）的遗传能力来进一步区分。源自银鼓鱼的该属所编码的CAZymes的分布在系统发育上并不保守。在亲缘关系密切的物种之间观察到不同的CAZyme基因组成。相反，在不同物种中发现了靶向相同底物的CAZyme基因簇（操纵子）。尽管如此，转录数据表明亲缘关系密切的该属靶向鱼类后肠内特定的底物组。结果突出了银鼓鱼后肠中该属的宿主特异性适应性，这可能有助于该属消化其海藻食物，以及这些该属物种具有多样且冗余的碳水化合物降解能力。
尽管有许多关于该属在人类和反刍动物中的报道，但其多样性和功能仍未得到充分研究，对于它对宿主健康是产生积极还是消极影响也没有明确的共识。鉴于肠道群落在银鼓鱼后肠中的共生作用（该属在银鼓鱼后肠中很普遍），以及所编码的碳水化合物活性酶（CAZymes）的多样性可能有助于分解宿主饮食中的重要底物，该属很可能为鱼类宿主提供重要服务。因此，在各种背景和宿主中考虑其代谢对于理解该属的生态学至关重要。我们的研究突出了基于宿主关联的该属的独特遗传特征，以及与鱼类相关的该属将大型藻类生物质转化为营养保健品（藻酸寡糖、β - 葡聚糖、硫酸化半乳聚糖和硫酸化岩藻聚糖）的潜力。
