极端嗜热厌氧纤维素菌的分离鉴定、系统发育分析及其酶学性质的研究

ISOLATION OF A THERMOPHILIC CELLULOLYTIC ANAEROBIC BACTERIUM AND ITS BIOLOGICAL CHARACTERISTICS

从云南高温温泉、油井等热源地区采集的大量样品中,获得了一株特殊的极端嗜热厌氧纤维素分解菌B2.分离菌株直杆,革兰氏阴性(G-),未观察到孢子,细胞单个或成对出现.菌体大小为0.4μm×(2-4)μm,严格厌氧,生长温度范围50-70℃,最适生长温度65℃.pH范围4-8,最适pH 7.0.在纤维素粉琼脂上菌落直径2-4 mm,乳白色.分离菌株能利用纤维二糖、葡萄糖、蔗糖、松子糖、淀粉、覃糖等作为碳源,分离菌株还可利用纤维素滤纸、纤维素粉、微晶纤维素、纤维素粉MN300和甘蔗渣、水稻秸杆.发酵纤维素产生乙醇、乙酸.在菌株B2的纤维素酶系中,C1酶、Cx酶和β-葡萄糖苷酶的最适温度分别为80℃、80℃和70℃,其比值为1:9:10,同时发现Cx酶具有较高的热稳定性.部分长度的16S rDNA序列分析表明,分离菌株B2与Thermoanaerobacter ethanalicus具有99.8％相似性.分离菌株B2为Thermoanaerobacter属.

Through selective enrichment culture, thermophlic cellulolytic anaerobic bacterium, strain B2 was isolated from hot pool in Yunnan, China. Its cells are straight with a size of rods 0. 4 μm×2-4μm, occurring both singly and in pairs. Gram staining reaction was negative. Endospores were never observed. It is strictly anaerobic and occurs over the temperature range between 50-70℃ with an optimum of 65℃. The pH ranges between 4-8 and the optimum is 7.0. On cellulose agar colonies of creamy colour are 2-4 mm in diameter. It uses monosaccharides,disacchrides and polysaccharides as carbon sources. The main fermentation end products on cellose medium are actate and lactate, and ethanol is also detected. The results show that the ratio a-mong C1 ,Cx and β-glucosidase is 1:9:10,the optimum temperature is 80℃, 80℃ and 70℃ ,respectively. Cx is found with high thermal stability. The phylogenetic analysis based on 16S rDNA suggests that strain B2 is closely related to Thermoanaerobact-er ethanalicus with 99.8% sequence similarity. Strain B2 is, therefore, a species Thermoanaerobacter. Fig 5, Tab 3 , Ref 21