不同铁、氮转化功能微生物对Fe(II)化学氧化的响应

Responses of Different Iron and Nitrogen Transformation Functional Microorganisms to Fe(Ⅱ) Chemical Oxidation

在地下水位波动带、地表水-地下水交互带等氧化还原变化区域,O_(2)会与Fe(Ⅱ)发生反应产生活性氧,如·OH、·O_(2)^(-)、H_(2)O_(2)等.这些活性氧具有生物毒性,可能对微生物的存活产生影响,而不同的功能微生物对Fe(Ⅱ)化学氧化产生活性氧的响应可能不同.为了验证这一科学假设,选取了一种Fe(Ⅱ)氧化菌Pseudogulbenkiania sp. strain 2002(strain 2002)和两种氨氧化细菌Rhodococcus sp.(A1)和Arthrobacter oxydans(A2)作为模式菌种,并与铁还原菌Shewanella oneidensis strain MR-1(MR-1)对比,研究了Fe(Ⅱ)化学氧化过程中微生物数量、细胞结构的变化,通过淬灭实验探究了活性氧的贡献.结果表明,不同功能微生物对Fe(Ⅱ)化学氧化的响应截然不同.0.2 mmol/L Fe(Ⅱ)氧化60 min后,MR-1数量下降了1.61个数量级,A1和A2分别下降了0.74和1.37个数量级,而strain 2002的存活几乎不受Fe(Ⅱ)氧化的影响.透射电镜观察结果显示,MR-1、A1和A2菌细胞的外膜受到了不同程度的破坏,而strain 2002完好无损.淬灭实验结果表明,溶液中和胞内生成的活性氧是造成功能微生物死亡的原因,但是不同微生物由于对Fe(Ⅱ)的吸附性能和对活性氧的抵御能力不同,因而对活性氧的响应机制不同.该研究结果对于诠释现代环境氧化还原变化区域微生物群落演化及地球史上氧气大爆发事件的生物地球化学过程具有重要的借鉴意义.

In redox fluctuation areas such as groundwater level fluctuation zone, surface water-groundwater interaction zone, O_(2) reacts with Fe(Ⅱ) to produce reactive oxygen species(ROSs), such as ·OH,·O_(2)^(-), H_(2)O_(2), etc. These ROSs are of biological toxicity and may have impact on the survival of microorganisms, and different functional microorganisms may respond differently to ROSs produced by Fe(Ⅱ) chemical oxidation. To validate this scientific hypothesis, a Fe(Ⅱ) oxidizing bacteria Pseudogulbenkiania sp. strain 2002(strain 2002), two ammonia oxidation bacteria Rhodococcus sp.(A1) and Arthrobacter oxydans(A2) were selected as model strains, and contrasted with the iron reducing bacteria Shewanella oneidensis strain MR-1(MR-1).The numbers of microorganisms, changes of cell structures, and the contribution of ROS were studied. The results show that different functional microorganisms respond differently to Fe(Ⅱ) chemical oxidation. After oxidation of 0.2 mmol/L Fe(Ⅱ) for60 min, the MR-1 numbers decreased by 1.61 orders of magnitude, A1 and A2 decreased by 0.74 and 1.37 orders of magnitude,respectively, while the survival of strain 2002 was virtually unaffected by Fe(Ⅱ) oxidation. It was observed through transmission electron microscope that the outer membranes of MR-1, A1 and A2 bacteria cells were damaged to varying degrees, while strain2002 was intact. The results of quenching test show that ROS produced in solution and in the cell caused death of functional microorganisms, but different microorganisms had different response mechanisms to ROS due to their adsorption ability to Fe(Ⅱ)and their resistance to ROS. The results of this study are of great significance for interpreting the microbial community evolution in the redox fluctuation region and the biogeochemical processes in the Great Oxygen Explosion in the history of the earth.