L. marina and microbes

Nematodes are the most abundant metazoans in marine sediments, many of which are bacterivores, however how habitat bacteria affect physiological outcomes in marine nematodes remains largely unknown. Here, we used a <i>Litoditis marina</i> inbred line to assess how native bacteria modulate host nematode physiology. We characterized seasonal dynamic bacterial compositions in <i>L. marina</i> habitats, and examined the impacts of 448 habitat bacteria isolates on <i>L. marina</i> development, then focused on HQbiome with 73 native bacteria, of which we generated 72 whole genomes sequences. Unexpectedly, we found that the effects of marine native bacteria on the development of <i>L. marina</i> and its terrestrial relative<i>Caenorhabditis</i><i> </i><i>elegans</i> were significantly positively correlated. Next, we reconstructed bacterial metabolic networks and identifiedseveral bacterial metabolic pathways positively correlated with <i>L. marina</i> development (e.g., ubiquinol and heme <i>b</i> biosynthesis), while pyridoxal 5’-phosphate biosynthesis pathway was negatively associated. Through single metabolite supplementation, we verified CoQ₁₀, heme <i>b</i>, acetyl-CoA, and acetaldehyde promoted <i>L. marina</i> development, while vitamin B6 attenuated growth. Notably, we found that only four development correlated metabolic pathways were shared between <i>L. marina</i> and <i>C. elegans</i>.Furthermore, we identified two bacterial metabolic pathways correlated with <i>L. marina</i> lifespan, while a distinct one in <i>C. elegans</i>. Strikingly, we found that glycerol supplementation significantly extended <i>L. marina</i> but not <i>C. elegans</i> longevity. Moreover, we comparatively demonstrated the distinct gut microbiota characteristics and their effects on <i>L. marina</i> and <i>C</i><i>.</i><i> </i><i>elegans</i><i> </i>physiology. Given that both bacteria and marine nematodes are dominant taxa in sedimentary ecosystems, the resource presented here will provide novel insights to identify mechanisms underpinning how habitat bacteria affect nematode biology in a more natural context. Our integrative approach will provide a microbe–nematodes framework for microbiome mediated effects on host animal fitness.