As^(3+)胁迫下Bacillus sp.ZJS3菌株的生理生化响应特性

Physiological and Biochemical Response Characteristics of Bacillus sp. ZJS3 Under As^(3+) Stress

研究菌株Bacillus sp.ZJS3在适宜生长条件下对As^(3+)胁迫的响应机制。本研究通过菌株Bacillus sp.ZJS3在固体培养基的长势确定耐受范围。在不同砷浓度影响条件下测定该菌株抗氧化酶活、丙二醛(malondialdehyde,MDA)含量及胞外聚合物(extracellular polymeric substances,EPS)中蛋白质和多糖含量。通过拍摄生物扫描电镜(scanning electron microscope,SEM),测定菌株的吸附率和氧化还原性以及检测耐受基因来研究菌株耐受机制。本研究确定了菌株Bacillus sp.ZJS3砷的耐受范围为100-300 mg/L。根据单因素实验结果,比较适宜培养条件pH为7.0、转速为200 r/min、温度为30℃。通过硝酸银染色实验和砷钼蓝法,检测到菌株能将As^(^(3+))氧化成As^(^(5+))。不同砷浓度胁迫下,过氧化物酶(peroxidase,POD)、过氧化氢酶(catalase,CAT)、超氧化物歧化酶(superoxide dismutase,SOD)和MDA含量明显升高且EPS内多糖含量持续升高,而蛋白质是先升高后降低。通过SEM观察到砷暴露后菌体形态逐渐变长且表面出现颗粒状的物质。在24 h内,该菌株对砷的最高吸附率为25.00%,吸附量为3.23 mg/g。Bacillus sp.ZJS3可将高毒性的As^(3+)氧化为低毒性的As^(5+),且对砷具有吸附作用,其抗氧化酶和胞外聚合物在砷胁迫过程发挥着重要作用。

We aim to investigate the response mechanism of strain Bacillus sp.ZJS3 to As^(^(3+))stress under optimal growth conditions.The tolerance range was determined by the growth of the strain Bacillus sp.ZJS3 in solid medium.The activities of antioxidant enzymes,the content of malondialdehyde(MDA)and the contents of protein and polysaccharide in extracellular polymeric substances(EPS)were determined under the influence of different arsenic concentrations.The mechanism of tolerance of Bacillus sp.ZJS3 was studied by photographing biological scanning electron microscope(SEM),measuring the adsorption rate and redox activity,detecting tolerance genes.The tolerance range of Bacillus sp.ZJS3 to As^(3+)was 100-300 mg/L.According to the single factor experiments,the suitable culture conditions were pH 7.0,rotation speed 200 r/min,and temperature 30℃.Through silver nitrate staining and arsenic molybdenum blue method,it was detected that Bacillus sp.ZJS3 oxidized As^(3+)to As^(5+).Under different arsenic concentration stress,the contents of peroxidase(POD),catalase(CAT),superoxide dismutase(SOD)and MDA increased significantly,and the polysaccharide content in EPS increased continuously,while the protein increased first and then decreased.It was observed by SEM that the cell morphology gradually lengthened and granular substances appeared on the surface after arsenic pollution.Within 24 h,the maximum adsorption rate of arsenic by the strain was 25.00%and the adsorption capacity was 3.23 mg/g.In conclusion,Bacillus sp.ZJS3 can oxidize high toxic As^(3+)to low toxic As^(5+),and has adsorption effect on arsenic.Its antioxidant enzymes and extracellular polymers play an important role in the process of arsenic stress.