奶牛瘤胃埃氏巨型球菌的分离鉴定及对乳酸发酵的影响

Isolation and identification of Megasphaera elsdenii in cow rumen and effect on lactic fermentation

采取健康奶牛瘤胃液,通过韦荣球菌科的特异性培养基分离得到了瘤胃厌氧菌株。该菌株是革兰氏阴性球菌,不能发酵大多数的碳水化合物和多元醇,但能发酵葡萄糖和果糖,不液化明胶,亦不能从硝酸盐生成亚硝酸盐,但能从半胱氨酸产生H2S,经形态学和生化反应特性分析初步鉴定为埃氏巨型球菌。通过细菌遗传学鉴定法16SrDNA PCR法,获得了527 bp的基因片段,测序分析证明与已报道的埃氏巨型球菌16S rDNA核苷酸序列的同源性可达98%;进一步确定所分离到的菌株为埃氏巨型球菌。同时观测了埃氏巨型球菌在体内、体外环境下对乳酸降解和挥发性脂肪酸生成的影响,结果表明,其能显著降低瘤胃液内乳酸的浓度,同时提高乙酸、丙酸、丁酸的浓度,且在一定时间范围内降低了乙酸与丙酸的物质的量比。上述结果为进一步研究瘤胃乳酸发酵调控提供了理论和实验基础。

In this test,a strain was isolated from ruminal fluids by using the VS blood agar plate which was specific for Veillonellaceae and the nutritive medium of Megasphaera elsdenii. And then the biochemistry and inherited characteristic of the isolated strain were identified using the biochemical event, the 16S rDNA gene technology and morphology. The results showed the isolated strain was Megasphaera elsdenii. In addition, by using the micro-ecosystem theory and utilizing the ability of the Megasphaera elsdenii that it could ferment lactic acid to propionic acid, impact of it on VFAs in culture solution and rumen fluids were observed both in vivo and in vitro fermentation experiments ,and the result provided the theory and experiment fundament for regulating lactic fermentation of rumen.