锑和砷对固氮菌的毒性效应及其机制研究

锑作为一种具有毒性和致癌性的类金属,其不合理的开发造成了严重的生态环境污染,尤其是土壤中高浓度锑和砷污染导致了环境中多种营养元素的缺乏。其中,氮素的缺乏严重阻碍了环境的恢复。然而,固氮微生物不仅能为氮素匮乏环境提供稳定的氮素来源,而且其固氮潜能可以作为监测土壤金属污染的敏感指标。为此,该文通过乙炔还原法(ARA)微宇宙培养试验手段,研究了不同价态锑和砷(三价及五价)在不同质量浓度(100、200、500、1 000、2 500、5 000 mg·L^-1)水平下对棕色固氮菌固氮潜能的影响,同时进一步探究了土壤固氮菌群落固氮潜能对土壤中主要锑和砷价态Sb(Ⅴ)和As(Ⅴ)]的响应机制。结果表明,锑和砷浓度与棕色固氮菌和土壤固氮微生物的固氮潜能均呈显著负相关,验证了以固氮微生物固氮潜能作为生物指示物的可行性。此外,Sb(Ⅴ)对土壤固氮微生物的毒性显著小于As(Ⅴ)。三价锑和砷污染对固氮菌固氮潜能的毒性高于五价As(Ⅲ)>Sb(Ⅲ)>As(Ⅴ)>Sb(Ⅴ)],这可能是由于Sb(Ⅲ)和As(Ⅲ)对细胞的致裂性强于Sb(Ⅴ)和As(Ⅴ)。相较于Sb(Ⅴ)和As(Ⅴ)对于棕色固氮菌固氮潜能的抑制作用,其对土壤固氮菌群落的固氮潜能的影响相对较弱。这一差异可能是由于土壤复杂的理化性质以及微生物群落和功能多样性而导致的。

Toxicity and Mechanism of Antimony and Arsenic on Azotobacter

As a toxic and carcinogenic metal, antimony has caused serious ecological pollution due to its extensive exploitation. The high concentrations of As and Sb also cause the lack of nutrients. Among them, the lack of nitrogen hinders the progress of environmental restoration. Nitrogen fixing microorganisms may provide organic nitrogen sources to these nitrogen-deficient environments. On the other side, these nitrogen fixing microorganisms may also be used as sensitive indicators to monitor soil metal pollution. In this study, the effects of different valence states(trivalent and pentavalent) and concentrations(100, 200, 500, 1 000, 2 500, and 5 000 mg·L^-1) of arsenic and antimony on the nitrogen fixation potential were examined by the acetylene reduction(ARA) test on Azotobacter vinelandii. Furthermore, the mechanism of the nitrogen fixation potential of the soil nitrogen-fixing microorganisms to the main antimony and arsenic species Sb(Ⅴ) and As(Ⅴ) ] in the soil was further examined. The results showed that the concentrations of antimony and arsenic were negatively correlated with the nitrogen fixation potential of Azotobacter vinelandii and nitrogen-fixing microorganisms in the soil, suggesting the feasibility of using nitrogen-fixing microorganisms as a biological indicator. In addition, Sb(Ⅴ) was less toxic to the soil nitrogen-fixing microorganisms than As(Ⅴ) . Sb(Ⅲ) and As(Ⅲ) was more toxic than Sb(Ⅴ) and As(Ⅴ) on Azotobacter vinelandii. This observation may attribute to the stronger cell cleavability of Sb(Ⅲ) and As(Ⅲ) than Sb(Ⅴ) and As(Ⅴ) . Overall, the toxicity of As and Sb species on nitrogen fixation can be ranked as As(Ⅲ)>Sb(Ⅲ)>As(Ⅴ) >Sb(Ⅴ) . The inhibition of As and Sb species is weaker on the soil nitrogen fixing microorganisms than those on Azotobacter vinelandii. This may be due to the complicated physiochemical properties and the diverse microbial communities in the soils.