Department of Marine Sciences, University of Georgia, Athens, GA 30602.
Complex Carbohydrate Research Center, University of Georgia, Athens, GA 30602.
Proc Natl Acad Sci U S A. 2020 Feb 18;117(7):3656-3662. doi: 10.1073/pnas.1917265117. Epub 2020 Feb 3.
In the nutrient-rich region surrounding marine phytoplankton cells, heterotrophic bacterioplankton transform a major fraction of recently fixed carbon through the uptake and catabolism of phytoplankton metabolites. We sought to understand the rules by which marine bacterial communities assemble in these nutrient-enhanced phycospheres, specifically addressing the role of host resources in driving community coalescence. Synthetic systems with varying combinations of known exometabolites of marine phytoplankton were inoculated with seawater bacterial assemblages, and communities were transferred daily to mimic the average duration of natural phycospheres. We found that bacterial community assembly was predictable from linear combinations of the taxa maintained on each individual metabolite in the mixture, weighted for the growth each supported. Deviations from this simple additive resource model were observed but also attributed to resource-based factors via enhanced bacterial growth when host metabolites were available concurrently. The ability of photosynthetic hosts to shape bacterial associates through excreted metabolites represents a mechanism by which microbiomes with beneficial effects on host growth could be recruited. In the surface ocean, resource-based assembly of host-associated communities may underpin the evolution and maintenance of microbial interactions and determine the fate of a substantial portion of Earth's primary production.
在富含营养的海洋浮游植物细胞周围区域，异养细菌通过吸收和分解浮游植物代谢物转化大量最近固定的碳。我们试图了解海洋细菌群落在这些营养增强的菌席中组装的规则，特别是要解决宿主资源在驱动群落聚集中的作用。用已知的海洋浮游植物外代谢物的不同组合接种海水细菌群落的合成系统，并每天转移群落，以模拟自然菌席的平均持续时间。我们发现，细菌群落的组装可以通过对混合物中每种单一代谢物上维持的分类群进行线性组合来预测，其权重是根据每种代谢物支持的生长情况确定的。尽管观察到了偏离这种简单的附加资源模型的情况，但当宿主代谢物同时存在时，通过增强细菌生长，也归因于基于资源的因素。光合作用宿主通过排泄代谢物来塑造细菌伴生物的能力代表了一种机制，通过这种机制，可以招募对宿主生长有益的微生物组。在海洋表面，基于资源的宿主相关群落的组装可能是微生物相互作用进化和维持的基础，并决定了地球大部分初级生产力的命运。
