【作者】 张磊；

【导师】 曲东；

【作者基本信息】 西北农林科技大学 ， 农业环境保护与食品安全， 2008， 硕士

【摘要】 本试验通过来源于不同水稻土微生物群落厌氧培养试验,以Fe(OH)3作为唯一电子受体研究了以纤维素粉作为电子供体时对氧化铁还原的影响。通过比较电子供体浓度与氧化铁还原能力的关系,以期明确不同来源的铁还原微生物对纤维素作为碳源时的利用特征。采用纯培养实验,进一步探讨一些分离纯化的铁还原菌株对纤维素粉的利用潜力。以土壤泥浆培养试验,研究了不同来源的纤维素在淹水条件下对土壤中微生物铁还原的影响,比较了对不同来源的有机物料在厌氧铁还原过程中的差异。对进一步阐明稻田生态系统中有机物代谢及其与微生物铁还原过程的关系提供了必要的理论依据。研究得出以下主要结论:(1)不同水稻土微生物群落利用纤维素的微生物铁还原能力具有显著的差异。由总体变化趋势来看,不同来源微生物群落利用纤维素的铁还原程度与设置纤维素浓度的大小成正比,Fe(II)的最终累积量表现为20 g/L处理>10 g/L处理>2 g/L处理,除TJ外的其余3种微生物群落利用浓度为20g/L的纤维素的Fe(II)浓度均可达到500 mg/L左右,接近添加的Fe(III)总量。随着添加纤维素浓度的增大,Fe(III)最大还原速率(Vmax)也表现出增大的趋势。从达到最大反应速率的时间来看,吉林和湖南水稻土微生物群落都随着添加纤维素浓度的增加,TVmax则由大变小。添加纤维素的浓度越高其到达最大反应速率的时间越早。在四川水稻土微生物群落中,不同浓度的纤维素处理到达最大反应速率的时间基本接近。(2)不同铁还原菌株利用纤维素的异化铁还原能力具有一定区别。菌株JX-a06、SC-a04、SC-a16和SC-a20在以纤维素为唯一碳源时其a较大,分别达到了71.82、76.68、79.92及71.07mg/L,Fe(III)还原率较高,分别达到21.16%、22.59%、23.55%和20.94%,菌株JX-a12、JX-a17、SC-a09、SC-a11、SC-a14和SC-a24的铁还原能力居中,分别达到16.17%~19.94%,而菌株JX-a03和JX-a08的铁还原反应活性较差,其Fe(III)还原率显著地低于其他菌株,仅为9.64%和9.66%。最大反应速率(Vmax)变化与其Fe(III)还原率变化趋势一致。12个菌株的TVmax分布在3.8d~5.7d,说明长期的纯培养过程对纤维素分解的促进作用并不明显。与接种不同水稻土微生物群落的铁还原过程相比,其Fe(II)累积量明显较低,说明试验中使用的12株具有铁还原能力的菌株直接利用纤维素碳源的能力是有限的,而纤维素的分解利用可能需要共代谢过程来加强,所以在水稻土微生物群落的铁还原过程中具有较高的铁还原效率。(3)从铁还原的程度比较,利用4种不同来源纤维素的能力表现为:三叶草﹥玉米芯﹥玉米秸杆﹥小麦秸杆。不同土壤微生物群落处理之间在玉米芯和小麦秸杆处理中有一定的差异,而在三叶草和玉米秸杆处理中其Fe(II)累积量基本相同。4种水稻土微生物群落利用不同来源纤维素时的Fe(III)还原率表现为:利用小麦秸杆时平均为35.28±8.05%,三叶草处理为76.38±3.32%,玉米芯处理为65.39±9.28%,玉米秸秆处理为48.64±7.58%,其变异系数(CV%)分别为22.83%、4.34%、14.19%和15.59%。由变异系数的变化说明,三叶草对4种水稻土微生物群落来说均属于易利用的碳源。4种水稻土微生物群落对小麦秸杆的利用率总体上说比较小,但不同水稻土微生物群落间相差较大;玉米秸秆和玉米芯作为碳源时,尽管Fe(III)还原率达到48.64%和65.39%,对碳源的利用率较高,但不同微生物群落间的变异系数亦达到15.59%和14.19%,利用率的差异比较明显。(4)添加Fe(OH)3及不同有机物料处理后对TJ水稻土的影响明显大于对SC水稻土的影响,反映了不同水稻土微生物铁还原过程的内在特征。四川水稻土中添加不同来源的纤维素的不同处理之间变化并不明显。CK的a值为6.130 mg/g,添加Fe(OH)3处理为6.513 mg/g,添加有机物料处理平均为6.233±0.215 mg/g,添加Fe(OH)3及不同有机物料处理为6.450±0.066 mg/g,总体上较CK有一定的增加,但变化并不明显。由Vmax变化看出,不同处理均较CK有明显增加,同时,TVmax在添加Fe(OH)3及不同有机物后都较之CK缩短。在TJ水稻土中,添加不同秸秆的处理,均表现为在前10天Fe(II)浓度增加迅速,随后变化缓慢,其中添加Fe(OH)3处理的Fe(II)产生量明显大于CK(自然土壤);秸秆加入可显著提高土壤中Fe(II)的累积量和生成速率,对土壤中的微生物铁还原具有明显的促进作用。TJ水稻土中添加Fe(OH)3处理的Fe(II)累积量(a)由CK的5.631 mg/g增加到5.905 mg/g,表明加入的Fe(OH)3能够迅速地被还原,其Vmax也由0.137 mg/(g·d)增加到0.245 mg/(g·d)。添加小麦秸杆、三叶草、玉米芯及玉米秸杆后,a值分别变化到6.046,6.209,6.461及6.467 mg/g,其增加量较添加Fe(OH)3处理高,表明有机物对TJ水稻土中铁还原的促进作用明显。对同时添加秸杆及Fe(OH)3处理,同样既增加了Fe(II)累积量(6.701~7.0 mg/g),又增加了Vmax(0.595~1.048 mg/g·d)。本研究通过厌氧泥浆培养、不同微生物群落混合培养和纯培养系统的研究了纤维素以及不同来源的纤维素对水稻土异化铁还原过程的影响。获得的主要结果为更全面的理解水稻土中异化铁还原过程提供了必要的理论依据。更多还原

【Abstract】 Microbial communities from different paddy soil are tested with anaerobic cultivations, and researches on the effect when using Fe (OH) 3 as the sole electron acceptor, the use of cellulose as the electron donor have on the iron reduction. By comparing the relationship of the electron donor concentration and iron reducibility, and try to clarify the utilization characteristics of different sources of iron reducing microbial when cellulose are used as the carbon source. Pure cultivation experiments are operated to further explore some of the isolation and purification of iron reducing strain on the potential for the use of cellulose powder. Test soil mud cultivation, study the impacts that cellulose from different sources under the condition of flooding have on the iron reduction of soil microbial, and compare the difference of organics of different resources during the iron reduction process which offer the necessary theoretical basis to further clarify the organic metabolism in the rice ecosystem and its relationship with microbial iron reduction. Main conclusions are drawn as follows:1. There are notable differences between microbial iron irreducibilities of different paddy soil microbial communities when use cellulose. Seen from the overall trend, the use of cellulose by different sources of microbial communities is proportional to the cellulose concentration, the performance of the final cumulant of Fe (II) are: treatment 20 g / L>treatment 10 g / L> treatment 2 g / L, with the exception of TJ, the remaining three kinds of microbial communities use concentration of 20 g / L starch Fe (II) concentration can be reached 500 mg / L, nearly added total Fe (III). With the addition of increasing concentrations of cellulose, Fe (III) reduction maximum rate (Vmax) also showed increasing trend. From the maximum rate of reaction time, Jilin and Hunan paddy soil microbial community, with the addition of increasing concentrations of cellulose, showed a turnaround from TVmax. The higher the adding cellulose concentration is the sooner it reaches its maximum rate. Microbial communities from Sichuan paddy soil took almost equal time to reach the maximum rate in dealing with different concentrations of cellulose.2. The reducibility of different iron reduction strains of using showed certain distinctions. When using cellulose as the sole carbon source, strain JX-a06、SC-a04、SC-a16 and SC-a20 all have large value of a, which respectively reached 71.82,76.68,79.92 and 71.07 mg / L, Fe (III) reduction is also high with the rate of respectively 21.16%, 22.59%, 23.55% and 20.94%, the iron of the strains JX-a12, JX-a17, SC -a09, SC-a11, SC-a14 and SC-a24 are among the middle, which respectively reached 16.17 percent to 19.94 percent, and strains JX-a03 and a08 JX-iron suffered with poor iron reducibility, among which the Fe (III) reduction rate was significantly lower than the other strains, with only 9.64 percent and 9.66 percent. The changes of maximum rate (Vmax) and the change rate of Fe (III) reduction are identical. TVmax of 12 strains are distributed between 3.8 d~ 5.7d, and which showed the role the long-term process of pure cultivation play in promoting cellulose decomposition is not obvious. Compared to the iron reduction which are inoculated with different soil microbial community from paddy soil, Fe (II) accumulation was significantly lower, which implies the capability of the 12 strains with iron reducing ability have limit direct use of cellulose carbon source, and the decomposition of cellulose may need the process of metabolism to strengthen, so in the paddy soil microbial community in the process of reduction of iron is with high iron reduction efficiency.3. Compare the extent of iron reduction, the abilities of using four different kinds of cellulose sources are: clover> corncob> corn straw> wheat straw. Between different treatments of soil microbial community in dealing with wheat straw and corn-cob are of some differences, and clover and corn straw in its handling of Fe (II) accumulation are basically the same. Four kinds of microbial communities from paddy soil, when use different sources of cellulose, Fe (III) reduction rates are as follows: The use of wheat straw are at an average of 35.28±8.05%, clover treatment are 76.38±3.32%, corn-cob treatment are 65.39±9.28%, and corn stalks treatment are 48.64±7.58%, the coefficient of variation (CV%) were 22.83%, 4.34%, 14.19% and 15.59% respectively. From the changes of the coefficient of variation, clover is a more easily used carbon source among four kinds of paddy soil microbial communities. The utilization of wheat straw for four kinds of paddy soil microbial community is relatively small, but among different paddy soil microbial communities, large difference are shown. When use maize stalks and corn-cob as carbon source, although Fe (III) reduction rate are of 48.64% and 65.39%, with high utilization of carbon sources, between different microbial communities, coefficient of variation also reached 15.59% and 14.19%, and the difference of utilization is more obvious.4. The impact of the addition of Fe (OH) 3 and different organic materials is significantly greater on TJ paddy soil than the impact on the soil of SC paddy soil; which reflect the intrinsic characteristics of different iron paddy soil microbial reduction. Changes of treatments with different sources of cellulose of Sichuan paddy soil are not significant. A value of CK is 6.130 mg / g, with Fe (OH) 3 adding in is 6.513 mg / g, treatment with organic material adding in are of an average of 6.233±0.215 mg / g, with Fe (OH) 3 and different organic materials adding in are 6.450±0.066 mg / g, on the whole, CK increases, but the change is not apparent. Seen from the changes of Vmax, different treatments all increased significantly than CK, while TVmax, after adding Fe (OH) 3 and different organic compounds all shortened than CK. For TJ paddy soil, treatments with different straws adding in, all appear increasing of the previous 10 days of Fe (II) concentrations, and then slow to change, addition of Fe (OH) 3 with Fe (II) produced significantly greater than in CK (natural soil); with straw added in can significantly enhance the cumulative production and producing rate of Fe (II), which played great role in improving rate of iron microbial reduction. TJ paddy soil added Fe (OH) 3 is with Fe (II) accumulation (a) from the CK 5.631 mg / g to 5.905 mg / g, that the accession of Fe (OH) 3 can be restored quickly, Vmax increased from 0.137 mg / (g ? d) to 0.245 mg / (g ? d). After adding wheat straw, clover, corn cob and corn straw, a value change to 6.046,6.209,6.461 and 6.467 mg / g, which show more increase than adding Fe (OH) 3, demonstrates the organic have great impacts on promoting Iron reduction in TJ paddy soil. Adding straw and Fe (OH) 3 at the same time, there is same increase in both the Fe (II) accumulation (6.701 to 7.0 mg / g), and Vmax (0.595 ~ 1.048 mg / g ? d).Through anaerobic mud test, mixed culture of different microbial community and the pure culture system, we study the different sources of cellulose, and the impact different sources cellulose have on paddy soil iron reduction. The main results of the study provided the necessary theoretical basis in understanding iron reduction in paddy soil.更多还原