富集培养下的若尔盖高原湿地低温纤维素降解细菌群落结构

Community structures of the cold-adapted cellulose-degrading bacteria in the Zoigê plateau wetland under enrichment culture conditions

若尔盖高原湿地常年低温,泥炭沼泽土分布广泛,为了解该特殊生境中的低温纤维素降解菌群落结构,将采自3个乡(阿西茸、黑河、达扎寺)的泥炭沼泽土样品于10℃条件下富集培养于羧甲基纤维素钠(CMC-Na)液体培养基中,用3,5-二硝基水杨酸(DNS)法测定纤维素酶活性,并利用变性梯度凝胶电泳技术(Denaturing gradient gel electrophoresis,DGGE)分析原始土壤样品和富集培养系中的细菌群结构.酶活测定结果表明,低温富集传代过程中,3个地区样品的相对酶活均随着培养代数的增加而增加,第3代的相对酶活最高,为25.5 U.DGGE分析表明:相对于原始土壤样品,富集系中的微生物菌群变简单;不同富集代数间,阿西茸乡样品细菌群落结构随传代次数增加而增加,而黑河乡和达扎寺乡样品表现为减少.对DGGE图谱条带序列的系统发育分析表明,富集培养系中的细菌属于α-变形菌纲(α-proteobacteria)、β-变形菌纲(β-proteobacteria)、γ-变形菌纲(γ-proteobacteria)、酸杆菌门(Acidobacteria)、疣微菌门(Verrucomicrobia)等类群.本研究结果揭示若尔盖高原湿地泥炭沼泽土低温纤维素降解菌种群丰富,具有潜在工业开发应用前景.(图3表2参35)

Peat swamp soil is widely distributed in the Zoig~ plateau wetland with an annual temperature below zero. Various cold-adapted cellulose-degrading bacteria developed in this low temperature ecosystem with low latitude （33°56＇N, 102°52＇E） and high altitude （3 300-3 600 m）. This study aimed to analyze the community structure of cold-adapted cellulose-degrading bacteria in this region. The peat swamp soil sample was enrichment cultured in the liquid medium with sodium salt of caboxy methyl cellulose （CMC-Na） at 10 ℃, and the cellulose activities of the enrichment culture was detected by 3,5-dinitrosalicylic acid （DNS） method. Denaturing gradient gel electrophoresis （DGGE） molecular technique was used to analyze the bacteria communities in the original soils and enrichment culture. The results showed an increase in the relative cellulose activities in all three peat swamp soils isolated from the Zoig6 Plateau wetland During the enrichment culture process. The cellulose activities of the enrichment culture reached the peak （25.5 U） at the third generation. The DGGE results showed lower diversity of the bacteria communities in the three different enrichment generations than in the original soil. Among the three generations, the bacteria communities＇ diversity in the A＇xi soil increased with the enrichment while the other two decreased. Phylogeny analysis based on the 16S rRNA sequences retrieved from the DGGE band showed that the bacteria species in the enrichment culture were closely related to bacteria affiliated to α-proteobacteria, β-proteobacteria, γ-proteobacteria, Acidobacteria and Verrucomicrobia, etc. Taken together, the present study suggested that cold-adapted cellulose-degrading bacteria abound in the peat swamp soil of the Zoig~ Plateau wetland, and these bacteria have potential prospect of industry application.