【作者】 贺江舟；

【导师】 曲东；

【作者基本信息】 西北农林科技大学 ， 土壤学， 2005， 硕士

【摘要】 Fe 在地壳中含量丰富,通常以各种Fe(III)氧化物的形式存在。厌氧条件下环境中的Fe(III)氧化物发生还原,并且这一过程主要是微生物介导的异化还原,即微生物以Fe(III)氧化物为最终电子受体的厌氧呼吸过程。异化Fe(III)还原具有重要的地学和环境学意义。含Fe(III)矿物的还原可促进Si、P等元素的释放,提高这些营养元素的有效性。异化Fe(III)还原微生物具有强大的代谢功能,它们可利用除Fe(III)以外的许多其它电子受体包括许多有毒重金属和类金属,如Mn(Ⅳ)、Cr(Ⅵ)、Co(III)、As(Ⅴ)、Se(Ⅴ)等以及放射性元素U(Ⅵ)、Tc(VII)、V(Ⅴ)等,从而对这些有毒重金属起到还原解毒或还原固定的作用。异化Fe(III)还原微生物在Fe(III)及金属氧化物的还原过程中可促进一些有机污染物,如芳香烃、卤代芳烃化合物、一些染料化合物及长链脂肪酸的降解。异化Fe(III)还原过程可有效的竞争厌氧环境中电子向产甲烷菌的流动,从而抑制甲烷气体的产生。一些异化Fe(III)还原微生物还可将电子传递向电极,产生电流,在清洁能源的生产上表现出了巨大的潜力。本文通过对采自四川、江西、吉林三个水稻土样土壤溶液的厌氧培养,初步探讨了不同基质对Fe(III)还原的影响,利用葡萄糖及不同有机酸时的Fe(III)还原,以及利用有机酸时温度对Fe(III)还原的影响,主要得到了以下结论: (1)添加适当浓度的NH4Cl、磷酸盐、KCl 对异化Fe(III)还原都具有不同程度的促进作用,加快Fe(III)还原,但对最终稳定状态的Fe(II)累积量影响不大。高浓度的磷酸盐对异化Fe(III)还原具有抑制作用,当磷酸盐的添加浓度达到44 mmol/L时,稳定状态时Fe(III)还原只有不添加处理Fe(III)还原的80%。添加较高浓度的NH4Cl和KCl时N、K 营养对异化Fe(III)还原的促进作用降低,推测Cl-对Fe(III)还原过程中的微生物及其活性有抑制作用。(2)NaCl对利用葡萄糖的异化Fe(III)还原有抑制作用。利用葡萄糖进行的发酵产酸过程比利用有机酸进行的异化Fe(III)还原过程对NaCl更敏感。当NaCl小于10.0 g/L时,它主要抑制的是葡萄糖的发酵过程。NaCl对利用葡萄糖的异化Fe(III)还原的抑制,可能主要是通过Cl-起作用。(3)在以葡萄糖、柠檬酸盐、琥珀酸盐、丙酮酸盐、丙酸盐、乙酸盐、甲酸盐为唯一碳源进行混合培养时,不同来源的微生物Fe(III)还原表现不同。Fe(III)还原时,四川水稻土的微生物对以上碳源物质都能迅速做出反应(表现为反应速率常数大,最大反更多还原

【Abstract】 Iron presents in abundance as variety of Fe(III) oxides in crust. Fe(III) in environment undergoes reduction under anaerobic condition. And this process is a microbial dissimilatory reduction, namely an anaerobic respiration with Fe(III) as the terminal electron acceptor. Dissimilatory Fe(III) reduction showed important geological and environmental significances. Fe(III) minerals reduction increases the release of Si, P, which results in a high availability of these nutrient elements for plant growth. The group of dissimilatory Fe(III) reducers showed a high capacity of metabolism, and could broadly use diverse electron acceptors including many toxic heavy metals and metalloids such as Mn(Ⅳ)、Cr(Ⅵ)、Co(III)、As(Ⅴ)、Se(Ⅴ) as well as some radioactive elements U(Ⅵ)、Tc(VII)、V(Ⅴ). Thus these organisms played a key role in reductive detoxification and immobilization of these toxic metals in environments. Under Fe(III) or other metal oxides reduction, the dissimilatory Fe(III) reducers could stimulate the decomposition of some organic contaminants including aromatic compounds, halogenated aromatics, some dyes and long-chain aliphatic acids. In anoxic environment, Fe(III) reduction also effectively outcompeted the electron flow to methanogenesis and inhibited methane production. Furthermore some dissimilatory Fe(III) reducing bacterial could transfer electron to electrode to generate electricity and showed promising potentials in clean energy generation. In this paper, three paddy soil samples collected from Sichuan, Jiangxi, Jilin were used and the soil solutions were incubated under anoxic atmosphere. The effects on Fe(III) reduction of different components in culture were investigated. And Fe(III) reductions utilizing glucose and simple organic acids were also preliminarily studied. Some conclusive results were obtained as following. (1) Adding suitable concentrated NH4Cl, phosphate and KCl in culture stimulated the Fe(III) reduction to some extent and accelerated the Fe(III) reduction, but affected the stable Fe(II) accumulation slightly. Higher phosphate concentration inhibited Fe(III) reduction. When the concentration of phosphate in the culture reached 44 mmol/L, the final Fe(II) accumulation was just 80% of the no addition control. Adding higher concentration of NH4Cl and KCl in the culture, the stimulation of Fe(III) by N and K nutrients decreased suggesting a possible inhibition of microbes and its activities in Fe(III) reduction by chloridion.. (2) NaCl inhibited the Fe(III) reduction utilizing glucose as substrate. The acidogenic fermentation of glucose maybe was more sensitive to NaCl than Fe(III) reduction in use of simple fatty acids produced in fermentation of glucose. And the fermentation of glucose was almost inhibited sufficiently when the salinity less than 10.0g /L of NaCl, in which the chloridion was the putative inhibitor. (3) Fe(III) reductions were distinct in the incubations of different microbes from the three paddy soil samples with glucose, citrate, succinate, pyruvate, propionate, acetate and formate as substrate respectively. Under Fe(III) reduction, the incubation of microbes from Sichuan paddy soil responded to these substrates quickly and showed a higher activity with highest values of k (Fe(III) reduction reaction rate constant), lowest values of Tvmax (incubation time of maximal reaction rate) and highest Fe(II) accumulation in unit carbon (pyruvate and propionate excluded ). Propionate was hardly used to reduce Fe(III) in the incubation of microbes from Jiangxi paddy soil, and succinate for Fe(III) reduction in incubation of microbes from Jilin paddy soil. Pyruvate could be readily used coincidently in the incubations of three paddies microbes under Fe(III) reduction showing some similarities in substrate utilities of microbes under Fe(III) reduction. (4) Logistc and exponential models could both well represent Fe(III) reduction process. Logistic formula was more suitable for modeling Fe(III) reduction in incubations at 30℃and exponential formula got satisfied fitting results for the Fe(III) reduction at 20℃and 10℃. (5) Activation energy was not suitable to represent the energy barriers in Fe(III) reduction, but could well indicate the sensitivity of Fe(III) reduction to temperature variation. The calculated activation energy in three paddies microbe incubation uniformly showed highest values for the utilities of pyruvate, medial for formate and lowest for acetate. Fe(III) reduction in incubations of microbes from Jilin paddy soil utilizing pyruvate and microbes from Sichuan paddy soil with acetate were impacted greatly by temperature variation from 10℃to 20℃. And other incubations were more sensitive to variation from 20℃to 30℃under Fe(III) reduction. Summarily incubations of microbes from Jilin paddy was not as sensitive as the other two paddy soil microbes incubation in Fe(III) reduction.更多还原