Microbiome and metabolome association network analysis identifies <i>Clostridium_sensu_stricto_1</i> as a stronger keystone genus candidate than <i>Bifidobacterium</i> in the gut of common marmosets

The common marmoset (<i>Callithrix jacchus</i>), a nonhuman primate species, is a model organism of great interest due to its translational value in a variety of research settings, including the field of microbiomics. While the composition of the marmoset's gut microbiome has been somewhat described in captivity, little is known about how gut microbiota interact with each other over time and how they relate to metabolite production. To help answer this, we characterized interactions in the gut microbiome of the common marmoset by calculating the Spearman correlation coefficient between 16S rDNA-derived relative genera abundance data and targeted metabolomics data collected longitudinally from 10 captive marmosets. Association network graphs were used to visualize significant correlations and identify genera and metabolites that have high degree centrality, marking them as more influential within the microbiome. The genus <i>Clostridium_sensu_stricto_1</i> engaged in the most metabolomic associations, indicating that it potentially plays a gatekeeping role over metabolites involved in microbial growth and signaling. Its associations with downregulated taurine and bile acids further suggest <i>Clostridium_sensu_stricto_1</i> modifies bile acids to exert its influence. <i>Flavonifractor</i> and several <i>Bacteroidales</i> members had the most bacterial associations and were negatively associated with <i>Bifidobacterium</i>, indicating a potential competitive relationship. To further characterize microbiome interactions, we performed hierarchical clustering on significant within-dataset associations and developed a new "Keystone Candidate Score" metric that identified <i>Clostridium_sensu_stricto_1</i> and <i>Alloprevotella</i> as the most influential bacteria (so-called candidate keystone genera) in the marmoset gut microbiome.IMPORTANCEPrevious studies have identified significant individuality within the gut microbiome of common marmosets. The reasons for this inter-subject variability and how it relates to health in captivity are poorly understood, owing to a lack of knowledge regarding dynamic interactions between specific microbiota. To that end, this study characterized significant temporal associations between the gut microbiome and metabolome of healthy captive marmosets. Our findings suggest that certain microbial taxa exert a stronger influence within the gut than others. Specifically, <i>Bifidobacterium</i> was the most abundant genus and primary driving force behind subject-specific microbiome differences, while Clostridium_sensu_stricto_1 and bacteria from the order Bacteroidales were the main sources, respectively, for significant bacteria-metabolite and bacteria-bacteria associations. Together, this suggests that <i>Bifidobacterium</i> may compete with the other taxa for resources and a metabolic niche in the marmoset microbiome.