Wong Mabel T, Wang Weijun, Lacourt Michael, Couturier Marie, Edwards Elizabeth A, Master Emma R
Department of Chemical Engineering and Applied Chemistry, University of Toronto, Toronto ON, Canada.
Front Microbiol. 2016 Jun 21;7:961. doi: 10.3389/fmicb.2016.00961. eCollection 2016.
Strategic enrichment of microcosms derived from wood foragers can facilitate the discovery of key microbes that produce enzymes for the bioconversion of plant fiber (i.e., lignocellulose) into valuable chemicals and energy. In this study, lignocellulose-degrading microorganisms from the digestive systems of Canadian beaver (Castor canadensis) and North American moose (Alces americanus) were enriched under methanogenic conditions for over 3 years using various wood-derived substrates, including (i) cellulose (C), (ii) cellulose + lignosulphonate (CL), (iii) cellulose + tannic acid (CT), and (iv) poplar hydrolysate (PH). Substantial improvement in the conversion of amended organic substrates into biogas was observed in both beaver dropping and moose rumen enrichment cultures over the enrichment phases (up to 0.36-0.68 ml biogas/mg COD added), except for enrichments amended with tannic acid where conversion was approximately 0.15 ml biogas/mg COD added. Multiplex-pyrosequencing of 16S rRNA genes revealed systematic shifts in the population of Firmicutes, Bacteroidetes, Chlorobi, Spirochaetes, Chloroflexi, and Elusimicrobia in response to the enrichment. These shifts were predominantly substrate driven, not inoculum driven, as revealed by both UPGMA clustering pattern and OTU distribution. Additionally, the relative abundance of multiple OTUs from poorly defined taxonomic lineages increased from less than 1% to 25-50% in microcosms amended with lignocellulosic substrates, including OTUs from classes SJA-28, Endomicrobia, orders Bacteroidales, OPB54, and family Lachnospiraceae. This study provides the first direct comparison of shifts in microbial communities that occurred in different environmental samples in response to multiple relevant lignocellulosic carbon sources, and demonstrates the potential of enrichment to increase the abundance of key lignocellulolytic microorganisms and encoded activities.
对源自食木动物的微观生态系统进行策略性富集，有助于发现关键微生物，这些微生物可产生将植物纤维（即木质纤维素）转化为有价值化学品和能源的酶。在本研究中，利用各种源自木材的底物，在产甲烷条件下对来自加拿大海狸（Castor canadensis）和北美驼鹿（Alces americanus）消化系统的木质纤维素降解微生物进行了3年多的富集培养，这些底物包括：（i）纤维素（C）、（ii）纤维素+木质素磺酸盐（CL）、（iii）纤维素+单宁酸（CT）和（iv）杨树水解物（PH）。在富集阶段，海狸粪便和驼鹿瘤胃富集培养物中，除了用单宁酸改良的富集培养物（其转化量约为0.15 ml沼气/mg添加的化学需氧量）外，用改良有机底物转化为沼气的效率均有显著提高（高达0.36 - 0.68 ml沼气/mg添加的化学需氧量）。对16S rRNA基因进行多重焦磷酸测序，结果显示厚壁菌门、拟杆菌门、绿弯菌门、螺旋体门、绿菌门和迷踪菌门的菌群随着富集过程发生了系统性变化。这些变化主要由底物驱动，而非接种物驱动，这一点通过UPGMA聚类模式和OTU分布得以揭示。此外，在用木质纤维素底物改良的微观生态系统中，多个分类谱系不明确的OTU的相对丰度从不到1%增加到了25 - 50%，包括来自SJA - 28纲、内共生菌纲、拟杆菌目、OPB54目和毛螺菌科的OTU。本研究首次直接比较了不同环境样本中微生物群落因多种相关木质纤维素碳源而发生的变化，并证明了富集培养在增加关键木质纤维素分解微生物及其编码活性丰度方面的潜力。
