Liu Liang, Tian Changfu, Wang Miaoxiao, Luo Ying, Huang Yaru, Jiang Tingting, Zhao Hongwen, Yu Qijun, Wang Entao, Yang Jinshui, Yuan Hongli
Department of Microbiology and Immunology, State Key Laboratory of Animal Biotech Breeding, and Key Laboratory of Soil Microbiology, Ministry of Agriculture, College of Biological Sciences, China Agricultural University, Beijing 100193, China.
Department of Microbiology and Immunology, State Key Laboratory of Plant Environmental Resilience, and Key Laboratory of Soil Microbiology, Ministry of Agriculture, College of Biological Sciences, China Agricultural University, Beijing 100193, China.
Proc Natl Acad Sci U S A. 2025 Jul 29;122(30):e2500664122. doi: 10.1073/pnas.2500664122. Epub 2025 Jul 21.
Natural biopolymer-degrading microbial communities drive carbon biogeochemical cycling. Within these communities, polymer degraders facilitate the growth of nondegraders by breaking down polymers through extracellular enzymes. However, the contributions of nondegraders to community dynamics, as well as the mechanisms that limit their access to degradation products, remain poorly understood. Here, we investigate EMSD5, a lignocellulose-degrading microbial community that efficiently converts corncob into isopropanol. We demonstrate that nondegraders, such as , enable the growth of degraders (e.g., sp. and ) by creating anaerobic conditions and supplying biotin. Within such expanded niches, lignocellulose degradation proceeds sequentially, and the availability of breakdown products to . is constrained by two interlinked processes. Specifically, sp. produces oligosaccharides that are largely inaccessible to . . A subset of these oligosaccharides is utilized by . to produce monosaccharides that support . growth, while glycosidase secretion by . is reduced under coculture conditions. Building on these findings, we designed a synthetic consortium by coculturing with an engineered . strain that expresses xylanase genes from an unculturable . This consortium achieved isopropanol production from hemicellulose without requiring anaerobic conditions. Our findings reveal the niche-expanding role of nondegraders and the processes that constrain their access to degradation products, offering insights into maintaining stable cooperation in biopolymer-degrading communities and designing efficient consortia for biopolymer conversion.
天然生物聚合物降解微生物群落驱动着碳的生物地球化学循环。在这些群落中，聚合物降解菌通过细胞外酶分解聚合物来促进非降解菌的生长。然而，非降解菌对群落动态的贡献以及限制它们获取降解产物的机制仍知之甚少。在这里，我们研究了EMSD5，一个能有效将玉米芯转化为异丙醇的木质纤维素降解微生物群落。我们证明，诸如 之类的非降解菌通过创造厌氧条件和供应生物素，使降解菌（如 菌属和 菌属）得以生长。在这种扩展的生态位中，木质纤维素的降解是依次进行的，并且降解产物对 的可用性受到两个相互关联的过程的限制。具体而言， 菌属产生的低聚糖 基本上无法被 利用。这些低聚糖中的一部分被 利用来产生支持 生长的单糖，而在共培养条件下， 分泌糖苷酶的能力会降低。基于这些发现，我们通过将 与一株经过基因工程改造的 菌株共培养，设计了一个合成菌群，该菌株表达了一种不可培养的 菌的木聚糖酶基因。这个菌群在不需要厌氧条件的情况下，从半纤维素中实现了异丙醇的生产。我们的研究结果揭示了非降解菌在扩展生态位方面的作用以及限制它们获取降解产物的过程，为维持生物聚合物降解群落中的稳定合作以及设计高效的生物聚合物转化菌群提供了见解。
