古尔班通古特沙漠地衣结皮中可培养细菌多样性初探

为了解古尔班通古特沙漠优势结皮类型--地衣结皮中可培养细菌的多样性，利用3种培养基经稀释涂布和划线分离得到18株纯培养菌株。对分离的所有菌株提取基因组DNA，利用细菌通用引物扩增得到16S rDNA的序列并测序。结果表明：（1）基于Ribosomal Database Project (RDP)在线归类分析，18株菌可初步归为3门3纲3目6科6属，未见新属，未分离到固氮菌属（Azotobacter）。其中，6株归为变形菌门(Proteobacteria)、6株属于放线菌门(Actinobacteria)、6株属于厚壁菌门 (Firmicutes); 不动杆菌属（Acinetobacter）、链霉菌属（Streptomyces）、芽孢杆菌属（Bacillus）为优势属，分别占分离菌株数的33%、28%、22%。（2）在EzTaxon-e数据库中对各菌株序列进行进一步的BLAST同源性分析表明，18株菌可进一步归为14个OTUs（Operational Taxonomic Unit），未见疑似新种（同源性均>97%），其中链霉菌属OTU比例最高（35.71%），依次为不动杆菌属和芽孢杆菌属（二者均为21.43%）。（3）古尔班通古特沙漠地衣结皮中的可培养细菌Shannon-Wiener多样性指数为2.5532，均匀度指数为0.9675。（4）上述可培养细菌在生物土壤结皮中具有固沙、加速矿化、生防等多重生态潜能。

Culture-dependent Bacteria Diversity of Lichen Crusts in the Gurbantunggut Desert

Lichen crusts is the main type biological soil crusts（BSCs） in the southern part of the Gurbantunggut Desert and served as one of the important nitrogen resource. It is also one of the sensitive biomonitors of desert ecosystem health, habitat heterogeneity and human induced disturbances. Using three different medium, 18 bacterial strains were isolated from lichen crusts. Phylogenetic analysis of partia1 16S rDNA sequences showed that: (1) These strains were clustered into 3 phyla, 3 classes, 3 orders, 6 families and 6 genera via Ribosomal Database Project (RDP) classifier. The phyla Proteobacteria, Actinobacteria and Firmicutes each owned 6 of the 18 strains. The dominant genera were Acinetobacter (33%), Streptomyces (28%) and Bacillus (22%). (2) Further classification of these strains was achieved via Basic Local Alignment Search Tool (BLAST) Homology analysis of the partial 16S rDNA against the EzTaxon-e database. BLAST results yielded 14 Operational Taxonomic Units (OTUs) and no novel species whose sequence similarity was lower than 97% compare to the species in the EzTaxon-e database.were obtained. Most of these OTUs belonged to the genus Streptomyces （35.71%）. (3) The Shannon-Wiener diversity index was 2.5532, a value lower than that of BSCs for the Hunsandake Desert. (4) These culture-dependent bacteria might play important roles in fixing sand particles, releasing plant-available nutrients from soil minerals and inhibiting the growth of plant pathogens, thereby promoting BSCs development.