Abstract: Straw returning can improve soil fertility, protect ecological environment and promote sustainable agricultural development. Soil microorganisms, especially those associated with cellulose degradation play an important role during the process of straw returning. The plate dilution method on carboxymethyl cellulose solid medium and enrichment method on Hutcherson filter paper strip liquid medium were used for cellulose-decomposing bacteria separation from soils long-term piled up with agricultural straw. The high efficiency cellulose decomposing bacteria were screened by Congo red staining and CMC enzyme activity assay. The culture characteristics, morphological characteristics and molecular biological methods were used to identify the bacteria strains. The weight loss rate of corn stalks, the content and degradation rate of cellulose, hemicellulose and lignin were determined to study the effect of cellulose-decomposing bacteria on degradation of corn stalks. And the effect of corn stalks powder treated by the strains on the growth of Perilla frutescens and Brassica napus was determined by pot experiments. The results showed that high-efficiency cellulose decomposition bacteria strains HLF4 and YDL3 were selected from the 16 isolated cellulose decomposition bacteria. The strain of YDL3 and HLF4 were identified as Bacillus subtilis and Streptomyces badius. The degradation powder of corn straw treated with single HLF4 and YDL3 strains and mixed strains were all better than the control. The weight loss rate, hemicellulose degradation rate, cellulose degradation rate and lignin degradation rate treated with mixed HLF4 and YDL3 strains were the highest, and were higher than the control by 52.00%, 46.65%, 42.11% and 31.19%, respectively. The enzymatic activities of SOD (superoxide dismutase), POD (peroxidase), and CAT (hydrogen peroxidase), as well as chlorophyll content and growth indexes of P. frutescens and B. napus treated by returning straw degraded with the cellulose decomposition bacteria were significantly higher than those of the control, the mixed treatment were the best one. Above all, HLF4 and YDL3 bacteria strains screened in present research had strong ability to decompose cellulose, and their mixed composition had the highest ability, which could be used as high-efficient cellulose decomposing bacteria in field planting.

Key words: cellulose decomposition bacteria, separation and identification, straw degradation, biological effects

摘要： 秸秆还田可以改善土壤肥力、保护生态环境、促进农业可持续发展，土壤微生物特别是与纤维素降解有关的微生物在秸秆还田过程中起关键性作用。从长期堆放农业秸秆的土壤中采用羧甲基纤维素固体培养基平板稀释法和赫奇逊滤纸条液体培养基富集法分离纤维素分解菌；刚果红染色法和CMC酶活力测定法筛选高效纤维素分解菌；采用培养特性、形态特征和分子生物学方法对菌种进行鉴定；通过测定秸秆失重率和纤维素、半纤维素和木质素的含量及降解率研究其降解玉米秸秆的效果；并测定其处理的玉米秸秆粉末对紫苏和油菜生长的影响。结果在分离到的16种纤维素分解菌中筛选出高效纤维素分解菌菌株HLF4和YDL3。HLF4和YDL3菌株分别鉴定为栗褐链霉菌（Streptomyces badius）和枯草芽孢杆菌(Bacillus subtilis)。HLF4和YDL3及混合菌株处理的玉米秸秆分解能力与对照相比均显著提高；其中HLF4+YDL3混合菌株处理效果优于单菌株，其玉米秸秆失重率、半纤维素降解率、纤维素降解率以及木质素降解率分别比对照高52.00％、46.65％、42.11％和31.19％。用纤维素分解菌酵解的秸秆还田处理的紫苏和油菜叶片的超氧化物歧化酶（superoxide dismutase，SOD）、过氧化物酶（peroxidase，POD）、过氧化氢酶（hydrogen peroxidase，CAT）活性和叶绿素含量以及生长指标均显著高于对照；特别是用HLF4+YDL3混合菌株处理的各项指标显著高于单菌株处理。筛选的HLF4和YDL3菌株分解纤维素能力较强，且其混合菌株的分解纤维素能力更强，可作为高效纤维素分解菌用于田间种植。

关键词: 纤维素分解菌, 分离鉴定, 秸秆降解, 生物效应