若尔盖高原湿地的真菌群落结构及低温纤维素降解真菌特征

Characteristics of Fungus Community Structure and Cold-adapted Cellulose-degrading Strains in Zoige Plateau Wetland

以若尔盖高原湿地的泥炭沼泽土壤为样,在利用变性梯度凝胶电泳技术(Denaturing gradient gel electrophoresis,DGGE)分析该生境真菌群结构的基础上,进一步通过可培养手段进行高效低温纤维素降解菌株的筛选。DGGE结果表明:阿西茸乡土样中真菌群落结构最复杂,其次是达扎寺乡、黑河乡。基于DGGE图谱条带序列的系统发育分析表明:若尔盖高原湿地中的优势真菌分属于白布勒弹孢酵母(Bulleromyces albus),曲霉属(Aspergillus),子黑附球菌(Epicoccum nigrum),假裸囊菌属(Pseudogymnoascus)和深色有隔内生真菌(Zalerion)等类群。通过纯培养从该区域分离到低温纤维素降解真菌50余株,其中S1和S7两株菌酶活最高,分别是9.36 U m L-1和23.01 U m L-1。系统发育分析显示菌株S1为白囊耙齿菌(Irpex lacteus),S7为烟曲霉(Aspergillus fumigatus)。两株菌对水稻秸秆表现出明显的降解效果,50d内S7对半纤维素、纤维素和木质素的降解率分别为46.57%,63.37%和30.74%;而S1对各组分降解率分别为30.02%,54.55%和22.95%。研究表明,若尔盖高原湿地泥炭沼泽土真菌群落结构复杂,具潜在应用价值。

In this study, the community structure of soil fungi in the peat swamp soil of the Zoige plateau wetland was analyzed by using the denaturing gradient gel electrophoresis （DGGE） method, and cold-adapted cellulose-degrading strains were isolated by a pure culture method. The DGGE results showed that the diversity of fungal community structure in Axirong area was higher than that in Heihe and Dazhasi areas. The phylogentic analysis based on the ITS sequences retrieved from the DGGE bandsshowed that the dominant fungal species in the Zoige plateau wetland were Bulleromyces albus, Aspergillus, Epicoccum nigrum, Geomyces, and Z^gerion. About fifty cold-adapted cellulose-degrading strains were isolated via the pure culture method from the peat swamp soil in the Zoige plateau wetland. Strain $1 and $7 had the highest cellulase activities, with a peak value of 9.36 U mL-1 and 23.01 U mL-1, respectively. Strain S1 was phylogenetically affiliated to Irpex lacteus while $7 belonged to AspergiUus fumigatus. These two strains showed remarkably degrading abilities to rice straw. Within 50 days, the degradation rate of hemicellulose, fibre, and hgnin in strain $7 was 46.36%, 63.27% and 30.14%, respectively, while that in strain S1 was 29.56%, 54.72% and 23.27%, respectively. This study suggested that the complex fungal community in the peat swamp soil of the Zoige plateau wetland had relative high cold-adapted cellulase activities could beapplied in degrading crop straw potentially.