海子水牛瘤胃微生物的宏基因组学分析

摘要

为系统探讨海子水牛瘤胃内的微生物组成及木质纤维素降解酶系,本试验利用基于高通量测序的宏基因组学技术对海子水牛(2.5岁左右,平均体重为493 kg)瘤胃液样本进行组学分析.结果表明,共获得了77283638条reads,并拼接出744712个scaffold.经prodigal分析后,共预测出827044个基因.通过基因注释发现海子水牛瘤胃中含有多种木质纤维素降解微生物,如生黄瘤胃球菌(Ruminococcus flavefaciens)、白色瘤胃球菌(Ruminococcus albus)、产琥珀酸丝状杆菌(Fibrobacter succinogenes)及栖瘤胃普雷沃氏菌(Prevotella ruminicola).此外,还发现有38011个基因编码蛋白质具有木质纤维素降解酶活性,其中糖苷水解酶(GH)基因数量最多(17877个),糖基转移酶(GT)(8637个)、碳水化合物结合模块(CBM)(4693个)和碳水化合物酯酶(CE)基因(4214个)数量次之,多糖裂合酶(PL)(1296个)和辅助氧化还原酶(AA)基因(934个)数量较少.在GH基因中,归属于GH2、GH43、GH97、GH3家族的基因较多,且编码蛋白质具有寡糖降解酶活性的基因数量最多.此外还发现了少量的纤维小体组分蛋白基因.结合其他物种肠胃宏基因组中GH基因比对分析,发现海子水牛瘤胃中的纤维素酶、半纤维素酶和分支降解酶比例与奶牛瘤胃较为接近.由此可见,海子水牛瘤胃内含有丰富的木质纤维素降解微生物及酶系,这将为筛选具有工业应用潜力的酶基因奠定理论基础.%In order to investigate microorganism composition and lignocellulolytic enzymes in rumen of Haizi buffalo, rumen fluid sample of Haizi buffalo ( about 2.5 years of age, average body weight was 493 kg) was surveyed using metagenomic high-throughput sequencing. The results showed as follws: a total of 77283638 reads were obtained, which were assembled into 744712 scaffolds. And then, a total of 827044 genes were predicted by prodigal analysis. Many microorganisms involved in lignocellulose degradation were identified by gene annotation, such as Ruminococcus flavefaciens, Ruminococcus albus, Fibrobacter succinogenes and Pre-votella ruminicola. We identified potential 38011 genes encoding lignocellulolytic enzymes including glycoside hydrolase (GH) (17877 genes), glycosyl transferase (GT) (8637 genes), carbohydrate binding module (CBM) (4693 genes), carbohydrate esterase (CE) (4214 genes), polysaccharide lyase (PE) (1296 genes), and auxiliary activity (AA) (934 genes). Among GH genes, most genes belonged to GH2, GH43, GH97 and GH3 families, and a higher abundance of oligosaccharide degrading enzymes in buffalo rumen met-agenome was identified. Besides that, we also predicted that some genes could encode the cellulosome compo-nent. Compared with GH genes in the gastrointestinal metagenome of other species, the proportions of cellu-lose, hemicellulase and debranching enzyme were similar between Haizi buffalo and dairy cow. These results demonstrate that buffalo rumen is considerably enriched in functional microorganisms and enzymes involved in lignocellulose degradation with great prospects to obtain enzyme genes that may be applied in the industry.