产多糖耐镉芽孢杆菌的筛选及其胞外聚合物的组成
时间:2018-11-01 17:55 来源:毕业论文 作者:毕业论文 点击:次
| 摘要：目前，土壤重金属污染尤其是镉（Cd）的污染日益严重，而在重金属污染的土壤中存在着多种耐重金属的真菌或细菌。利用微生物修复土壤镉（Cd）污染效果好，成本低，因此受到越来越多关注，而芽孢杆菌对环境适应性较强，能够高效地吸附镉，因此深入研究芽孢杆菌对土壤 Cd 污染修复具有重要的意义。本项目通过从重金属污染较严重的矿区土壤中筛选出三株耐镉芽孢杆菌，分别命名为B1、B2、B3，研究不同镉浓度下的细菌生长曲线及其胞外聚合物含量的变化，结果表明三株菌中，菌株B1与B3在120 mg/L Cd2+下仍能保持较高生长量，但菌株B2在高浓度镉离子下无法生长，50 mg/L Cd2+下能够正常生长；对比不同镉离子浓度处理下菌株胞外聚合物含量变化，发现细菌胞外多糖及胞外蛋白与镉离子浓度呈正相关趋势，该结果为高重金属抗性菌株的选择及修复重金属污染的土壤提供科学的理论依据。29876 毕业论文关键词：镉污染；重金属胁迫；芽孢杆菌；胞外聚合物；微生物修复 Screening of cadmium resistant Bacillus producing polysaccharide and its composition of extracellular polymeric substances Abstract：At present, the soil heavy metal pollution especially cadmium (Cd) pollution is becoming increasingly serious, people have pay more and more attention to it. In the soil contaminated by heavy metals, there are many kinds of fungi or bacteria that are resistant to heavy metals. Microbial remediation of soil cadmium (Cd) pollution has good effect, low cost, and has attracted more and more attention. Bacillus is more adaptable to environment and can absorb cadmium efficiently, so it is of great significance to study further about the effect of Bacillus on remediation of cadmium pollution in soil. Three cadmium tolerant Bacillus strains were isolated from the soil polluted by heavy metals, named B1, B2 and B3 respectively. The growth curve of three strains under cadmium ions exposure and the content of extracellular polymeric substances were studied. The results showed that among the three strains, B1 and B3 strains in 120 mg/L Cd2+ solution can still maintain a high growth rate, but the strain B2 can not grow in high concentrations of cadmium ions, and had the normal growth of 50 mg/L Cd2+ solution. Compared with the variation of extracellular polymeric substances under different cadmium ion concentrations, it was found that the extracellular polysaccharide and extracellular protein of bacteria were positively correlated with the concentration of cadmium ion, and the results provided a scientific basis for the selection of high heavy metal resistant strains and for the remediation of soil contaminated by heavy metals. Key words: Cadmium pollution; heavy metal stress; Bacillus; extracellular polymeric substances; microbial remediation 目 录 摘要1 关键词1 Abstract1 Key words1 引言1 1.1 实验材料 2 1.1.1 土样2 1.1.2 培养基2 1.1.3 主要试剂与溶液2 1.1.4 主要仪器设备3 1.2 实验方法 3 1.2.1 产多糖芽孢杆菌筛选3 1.2.2 菌株的菌落和菌落形态特征3 1.2.3 菌株革兰氏染色3 1.2.4 生长曲线的测定3 1.2.5 胞外聚合物(EPS)的提取及组成测定4 1.2.6 细菌基因组DNA的提取5 1.2.7 菌株种属鉴定6 2 结果与分析6 2.1 筛选产多糖芽孢杆菌6 2.2 不同镉浓度下对菌生长的影响7 2.3 胞外多糖含量的测定结果9 2.4 胞外蛋白质含量的测定结果9 2.5 系统发育树的构建10 3 讨论 12 4 结论 12 致谢13 参考文献13 产多糖耐镉芽孢杆菌的筛选及其胞外聚合物的组成 随着人类对于矿产资源的不断开发利用，大量有毒有害重金属被排放到土壤之中，重金属在土壤中含量超负荷，从而导致了土壤中重金属污染。目前，在重金属污染的土壤之中往往有铬（Cr）、镉（Cd）、铅（Pb）、汞（Hg）、砷（As）等重金属含量超标[1]。重金属产生后一旦进入到土壤之中，土壤中重金属超标会使得作物中的重金属含量增高，难以被生物降解，并且会通过食物链或者其他途径在不同程度上直接或间接地危害着人类的健康与生命，可能会造成难以弥补的后果。因此，目前在农业环境中亟需解决的一个重要问题就是治理土壤中重金属污染带来的各种问题。 (责任编辑：qin) |