Mangrove soil is a reliable source for screening cellulose-degrading bacteria due to the high diversity of microbes. To effectively utilize crop straw resources, a cellulolytic bacterium, Paenibacillus silvae strain CH2 was isolated from mangrove soil. We determined the carboxymethyl cellulose (CMC) and filter paper assay (FPA) activities of CH2 at different incubation times, NaCl concentrations, pH and temperatures, estimated the degradation efficiencies of rice and maize straw by CH2, sequenced and analyzed the whole genome of CH2. The results showed that along with the increases of incubation time, NaCl concentration, pH and temperature, the CMC and FPA activities increased first and then decreased . The highest CMC and FPA activities were observed at incubation time of 72-84 h, NaCl concentration of 6.0 g·L-1, pH of 7 and temperature of 36 ℃. Degradation of straw assays revealed that CH2 could effectively degrade rice and maize straw. At 0 g·L-1 NaCl (the control), the 10-day degradation rates of rice and maize straw were 30.4% and 47.0%, respectively. In the presence of 15 g·L-1 NaCl, the degradation rates were not significantly different from the control, indicating that CH2 had a high tolerance to salts. The whole genome of P. silvae CH2 was 6797325 bp, containing 6312 coding genes. P. silvae CH2 contained multiple genes encoding cellulose and hemicellulose degrading enzymes. These enzymes mainly belonged to the GH family, including endo-1,4-β-xylanase, Xylan 1,4-β-xylosidase, β-glucosidase, and endoglucanase. The results indicated that the bacterium had the potential to be used in crop straw degradation.
红树林土壤微生物种类丰富,是筛选纤维素降解菌的可靠来源。为了有效利用农作物秸秆资源,本研究从红树林土壤中筛选出一株具有纤维素降解能力的类芽孢杆菌CH2,研究不同培养时间、NaCl浓度、pH值和温度下羧甲基纤维素酶(CMC)和滤纸分解酶(FPA)活性,测试其对水稻和玉米秸秆的降解能力,并对CH2进行基因组测序和分析。结果表明: 随着培养时间、NaCl浓度、pH值和温度的提高,CMC和FPA活性均呈先上升后下降的趋势。培养时间72～84 h、NaCl浓度6.0 g·L-1、pH 7及36 ℃条件下,CMC和FPA活性均最高。对水稻和玉米秸秆的降解试验显示,CH2可有效降解水稻和玉米秸秆,在0 g·L-1 NaCl(对照)条件下,10 d降解率分别为30.4%和47.0%,且在15 g·L-1 NaCl条件下,降解率与对照组无显著差异,表明菌株CH2具有良好的耐盐性。基因组测序显示,CH2基因组为6797325 bp,包含6312个编码基因。基因组注释结果显示,CH2含有多个纤维素和半纤维素降解酶基因,这些酶主要隶属于GH家族,包括内切-1,4-β-木聚糖酶、木聚糖1, 4-β-木糖苷酶、β-葡萄糖苷酶和内切葡聚糖酶。该菌具有应用于农作物秸秆降解的潜力。.
Keywords: lignocellulose; mangrove forest; salt tolerance; straw; whole genome.