基于磁性纳米颗粒分选的土壤活性纤维素降解微生物富集研究

磁性纳米粒子介导分离（magnetic nanoparticle-mediated isolation, MMI）技术是从复杂微生物群落中鉴定分离具有特定代谢功能活性物种的有力工具。针对我国江西鹰潭水稻土三种不同施肥模式（不施肥CK、化肥NPK和有机肥OM），利用MMI技术定向富集活性纤维素降解细菌。结果表明，与不施肥相比，施肥可提高微生物数量和活性，增加拟杆菌门与厚壁菌门（特别是紫单胞菌科与类芽孢杆菌科）等活性纤维素降解细菌的占比，同时降低活性微生物种间依赖性，进而加速羧甲基纤维素钠的降解；此外，有机肥还增加了微生物生态网络中的潜在生态功能模块数量，因而效果好于化肥。以上结论与基于DNA稳定性同位素核酸探针（DNA-based stable isotope probing，DNA-SIP ）技术的结论一致，进而证明了MMI技术用于鉴定分离活性纤维素降解菌的可行性，同时本结果也为农田秸秆的资源化管理提供理论依据和实际指导。

The Responses of Active Cellulose-degrading Bacterial Community to Different Fertilization in Paddy Soils as Revealed by Magnetic Nanoparticle-mediated Isolation Method

Magnetic nanoparticle-mediated isolation(MMI)method is a promising technology for separating functional microbes from complex microbiota. In this study, we employed the MMI method to recover metabolically active cellulose decomposers from paddy soils with a 28-year history of different fertilization regimes(chemical fertilizers; termed NPK afterwards), organic amendments(OM), and without fertilization(CK)). Our findings suggest that compared to no fertilization, fertilization increased the number and activity of microorganisms, thereby facilitating cellulose degradation. These active cellulose-degrading bacterial phylotypes mainly belong to Bacteroides and Firmicutes at the phylum level, and further to Porphyromonadaceae and Paenibacillaceae at the family level. Also, we found that fertilization increased community stability, partly by decreasing interspecies dependency. Furthermore, OM fertilization increased the numbers of potential ecological function, which makes it more effective than NPK fertilization. These results were consistent with our previous conclusions based on DNA-SIP technology, suggesting that MMI is a powerful approach to recover active cellulose decomposers from a complex microbial community. Above all, these results would deepen our understanding of keystone straw decomposers in paddy soils and their shifts in response to different fertilizations.