一株秸秆促腐枯草芽孢杆菌的筛选鉴定及全基因组分析

Screening, identification, and genome-wide analysis of a straw-degrading strain of Bacillus subtilis

摘要:

【背景】 提高秸秆腐解效率是改善土壤质量、阻止土壤退化的重要途径。【目的】 拟筛选抗逆性强秸秆腐解效率高的微生物，优化其培养条件，并分析功能基因。【方法】 首先从北方低温干旱区获得土样，利用水解圈法、相对细胞密度法和酶活测定法等筛选秸秆促腐菌，表征其生物学特性，开展田间腐解试验，基因组测序分析功能基因。【结果】 筛选分离出抗逆性好的堆肥芽孢杆菌(Bacillus stercoris) HS6-2，大田腐解试验表明该菌对秸秆30 d和180 d的腐解率达55.74%和84.77%，较对照组提高了25.2%和11.99%；最优条件下该菌内切纤维素酶、外切纤维素酶和滤纸酶活分别可达到3.63、12.27和3.48 U/mL；全基因组测序分析表明，CAZy家族基因由189个基因编码，包括71个糖苷水解酶，涉及多种木质纤维素降解的酶基因。【结论】 菌株HS6-2具有轻度嗜盐、嗜碱、耐干旱、耐低温特性，在腐解秸秆方面具有很好的应用潜力，为秸秆还田菌剂的研发提供了重要的技术支持。

关键词:秸秆促腐菌;枯草芽孢杆菌;抗逆性;发酵优化;全基因组

Abstract:

[Background] Increasing the straw degradation efficiency is a key path to improve soil quality and curbing soil degradation. [Objective] To screen out the strains with strong degradation effect on straw, optimize the culture conditions and mine the functional genes of the strain. [Methods] Soil samples were collected from a low-temperature and arid area in northern China. The hydrolysis circle assay, cell density assay, and enzyme activity measurement were employed to screen the isolates and characterize the strain screened out. Field degradation experiments were carried out, and functional genes of the strain were mined by whole genome sequencing. [Results] Bacillus stercoris HS6-2 with strong stress tolerance was isolated. In the field, this strain showed the straw degradation rates of 55.74% and 84.77% after rooting for 30 and 180 days, respectively, which were 25.2% and 11.99% higher than those in the control. Under the optimized conditions, the strain showed the endo-cellulase, exo-cellulase, and filter paper enzyme activities of 3.63, 12.27, and 3.48 U/mL, respectively. The results of whole genome sequencing showed that the CAZy family members were encoded by 189 genes, including 71 glycoside hydrolases, some of which were involved in lignocellulose degradation. [Conclusion] HS6-2 as a mildly halophilic and basophilic strain with tolerance to drought and low temperatures demonstrates good application potential in straw degradation, which provides technical support for the research and development of microbial agents serving straw returning.

Key words:straw-degrading microorganisms;Bacillus subtilis;stress tolerance;fermentation optimization;whole genome