Widespread effects of catecholamines on growth of human gut bacteria.

The interactions between hosts and their microbiomes are driven in part by chemical communication, which influences immune responses, metabolism, and microbial community structure. Neuroendocrine signals are central to this bidirectional communication, forming the basis of microbial endocrinology. Although host-derived hormones, including catecholamines, are known to affect microbial physiology, much of the existing literature focuses on a limited number of model organisms or complex in vivo systems, where disentangling direct microbial responses from host-mediated effects is challenging. As a result, systematic comparative analyses of direct bacterial responses under controlled conditions remain scarce. Here, we performed a systematic in vitro screen under anaerobic conditions to assess catecholamine effects on the growth dynamics of phylogenetically diverse human gut bacteria. Catecholamines altered multiple growth parameters in a species-specific manner, with effects detectable at nanogram concentrations. Multivariate analyses, including principal component analysis and non-metric multidimensional scaling, revealed lineage-associated response patterns across taxa. Although derived from monoculture experiments, these intrinsic responses provide a comparative framework for understanding how direct hormone-microbe interactions may contribute to microbiome dynamics under host stress. Overall, this study provides a quantitative cross-species dataset to inform future systems-level investigations in microbial endocrinology.