Cd胁迫下枯草芽孢杆菌B12产表面活性素及其对生物被膜形成和Cd去除的影响

Surfactin production by Bacillus subtilis B12 under Cd stress and its effect on biofilm formation and Cd removal

摘要:

【背景】枯草芽孢杆菌可通过群集的方式形成生物被膜，而生物被膜在去除重金属方面发挥着重要作用。【目的】探究枯草芽孢杆菌(Bacillus subtilis) B12缓解Cd (CdSO4)胁迫的机制。【方法】考察Cd胁迫对B12生物被膜形成的影响，用酸沉淀法、反相高效液相色谱和液质联用分析(LC-MS)对有无Cd胁迫条件下菌株B12分泌的脂肽化合物进行提取、纯化和主要成分鉴定，并探究该主要成分对枯草芽孢杆菌(Bacillus subtilis) B12、苜蓿中华根瘤菌(Sinorhizobium meliloti) Mr40、解淀粉芽孢杆菌(B. amyloliquefaciens) P29生物被膜形成和吸附Cd的影响。【结果】在含Cd浓度为0?1.0 mg/L的Msgg培养基中，B. subtilis B12生物被膜干重显著增加。Cd胁迫促进菌株B12分泌脂肽化合物，其中表面活性素(Surfactin)含量增加。在含Cd浓度为0.5 mg/L的Msgg培养基中添加Surfactin后，菌株B12、Mr40、P29生物被膜干重比未添加时显著增加84.1%?126.9%，浮游细胞数量显著下降46.9%?55.3%，3株菌株对Cd去除率显著增加23.0%?36.1%，浮游细胞吸附Cd比例显著下降，生物被膜吸附Cd比例显著增加了46.8%?68.1%。【结论】Cd胁迫下菌株B12通过分泌更多的Surfactin来调控自身以及其他菌株生物被膜的形成来吸附更多的Cd，从而缓解Cd胁迫。

Abstract:

[Background] Bacillus subtilis can form biofilm by clustering, and biofilm plays an important role in the removal of heavy metals. [Objective] The purpose of this study was to examine the interactions of Bacillus subtilis B12 biofilm and lipopeptide compounds and cadmium removal, investigating the mechanism of B. subtilis B12 in alleviating Cd (CdSO4) stress. [Methods] Firstly, the effect of Cd stress on the formation of strain B12 biofilm was investigated. The lipopeptide compounds secreted by B12 strain under Cd stress were extracted, purified and identified by acid precipitation, reversed-phase high performance liquid chromatography (RP-HPLC) and liquid mass spectrometry (LC-MS). The effects of this major component on the biofilm formation and Cd adsorption of B. subtilis B12, Sinorhizobium meliloti Mr40 and B. amyloliquefaciens P29 were investigated. [Results] When 0?1.0 mg/L CdSO4 was applied in Msgg media, the dry weight of B. subtilis B12 biofilms increased significantly. Cd stress promoted the secretion of lipid peptide compounds by strain B12, and the content of surfactin was increased. In the Msgg media with 0.5 mg/L Cd concentration, biofilms dry weight of strains B12, Mr40, P29 were increased by 84.1% to 126.9% significantly when the strains were exposed to surfactin compared to control medium, whereas the planktonic cells counts were reduced significantly from 46.9% to 55.3%. Meanwhile, Cd removal rate of three strains were significantly increased by 23.0%–36.1%, biosorption capacities of Cd onto the strains biofilms significantly increased by 46.8% to 68.1%. [Conclusion] These findings suggest that B. subtilis B12 under exposure to Cd could trigger the effect of stronger surfactin and biofilm formation, and subsequent increased Cd absorption of the biofilms, thereby protecting them from Cd stress.