Microbial Systems Ecology Group, Department of Environmental Systems Sciences, Institute of Biogeochemistry and Pollutant Dynamics, ETH-Zurich, Zurich 8006, Switzerland.
Department of Environmental Microbiology, Eawag: Swiss Federal Institute of Aquatic Sciences, Duebendorf 8600, Switzerland.
Proc Natl Acad Sci U S A. 2023 Oct 31;120(44):e2305198120. doi: 10.1073/pnas.2305198120. Epub 2023 Oct 25.
Microbial communities perform essential ecosystem functions such as the remineralization of organic carbon that exists as biopolymers. The first step in mineralization is performed by biopolymer degraders, which harbor enzymes that can break down polymers into constituent oligo- or monomeric forms. The released nutrients not only allow degraders to grow, but also promote growth of cells that either consume the degradation products, i.e., exploiters, or consume metabolites released by the degraders or exploiters, i.e., scavengers. It is currently not clear how such remineralizing communities assemble at the microscale-how interactions between the different guilds influence their growth and spatial distribution, and hence the development and dynamics of the community. Here, we address this knowledge gap by studying marine microbial communities that grow on the abundant marine biopolymer alginate. We used batch growth assays and microfluidics coupled to time-lapse microscopy to quantitatively investigate growth and spatial distribution of single cells. We found that the presence of exploiters or scavengers alters the spatial distribution of degrader cells. In general, exploiters and scavengers-which we collectively refer to as cross-feeder cells-slowed down the growth of degrader cells. In addition, coexistence with cross-feeders altered the production of the extracellular enzymes that break down polymers by degrader cells. Our findings reveal that ecological interactions by nondegrading community members have a profound impact on the functions of microbial communities that remineralize carbon biopolymers in nature.
微生物群落执行着重要的生态系统功能，如将存在于生物聚合物中的有机碳进行再矿化。矿化的第一步是由生物聚合物降解菌完成的，这些菌携带能够将聚合物分解为寡聚或单体形式的酶。释放的营养物质不仅允许降解菌生长，还促进了消耗降解产物的细胞的生长，即利用者，或消耗降解菌或利用者释放的代谢物的细胞，即清道夫。目前尚不清楚这些再矿化群落如何在微观尺度上组装——不同类群之间的相互作用如何影响它们的生长和空间分布，从而影响群落的发展和动态。在这里，我们通过研究在丰富的海洋生物聚合物海藻酸盐上生长的海洋微生物群落来解决这一知识空白。我们使用批量生长测定和微流控技术结合延时显微镜来定量研究单细胞的生长和空间分布。我们发现，利用者或清道夫的存在会改变降解菌细胞的空间分布。一般来说，利用者和清道夫——我们统称为交叉喂养细胞——会减缓降解菌细胞的生长速度。此外，与交叉喂养细胞共存会改变降解菌细胞产生的分解聚合物的胞外酶。我们的发现表明，非降解群落成员的生态相互作用对微生物群落在自然中再矿化碳生物聚合物的功能有着深远的影响。
