Rotation benefit and population changes of soil hydrogen oxidizing bacteria in legume crop fields

豆科植物(如大豆、紫花苜蓿等)的根瘤细胞内的细菌可以将氮气固定成一种形式的氮，植物可以用这种形式来制造蛋白质和核酸。氢气是固氮酶固氮酶的副产品，占流向该酶的能量的33%(另外67%用于还原氮气)。豆科植物根瘤会产生大量的氢气，并将其释放到土壤中。例如，仅在加拿大的紫花苜蓿作物中，我们估计每年可能有多达24亿升氢气释放到加拿大农业土壤中。如果考虑其他豆类作物，全国的氢气产生率可能会高出一倍。这种氢气生产可以使用整个工厂光合作用产生的能量每天净增加的6%。我们不明白为什么进化过程、农作物的植物育种或最佳固氮菌的选择不能减少所有豆类的能量损失。豆类是与其他作物(特别是谷类作物)轮作的理想作物，可显著提高后一种作物的生长和产量。研究人员还无法确定这种增产的基础。只有大约25%的非豆科作物的生长增长可以归因于氮素营养的改善。其余75%的影响无法解释。我们提出，根瘤释放的氢刺激和支持某些土壤氢氧化菌的生长。这些细菌反过来促进植物生长。土壤的这种氢肥可能解释了豆类对非豆类生长的有利影响。本研究的目的是1)分析土壤根瘤附近土壤细菌群落结构的变化，2)鉴定和鉴定土壤中的氢氧化菌，3)了解土壤中氢氧化菌与土壤肥力的关系。本研究的长期目标是了解植物根系与土壤微生物的关系，特别是那些促进非豆科作物生长的微生物，为农业生产提供实用的方案或接种剂。

Root nodules of legumes (e.g. soybeans, alfalfa, etc.) have intracellular bacteria that can fix nitrogen gas into a form of nitrogen that the plant can use to make protein and nuclei acids. Hydrogen gas is a byproduct of the nitrogen fixing enzyme, nitrogenase, claiming about 33% of the energy that flows to the enzyme (the other 67% is used to reduce nitrogen gas). Legume nodules produce a large quantity of hydrogen gas, and release this into soils. For example, in Canadian alfalfa crop alone, we have estimated that there may be as much as 2.4 thousand million liters of hydrogen gas released to Canadian agricultural soils every year. If other legume crops are considered, the national hydrogen gas production rate may be twice as high. This hydrogen gas production can use up to 6% of the net daily gain of photosynthetically derived energy of the entire plant. We do not understand why evolutionary processes, plant breeding of agricultural crops, or selection of optimal nitrogen fixing bacteria has not reduced this energy loss in all legumes. Legumes are ideal crops to use in rotation with other crops (especially cereal crops), resulting in a significant increase in the growth and yield of the subsequent crop. Researchers have not been able to determine the basis for this yield enhancement. Only about 25% of the increase in the growth of the non-legume crop can be attributed to improved nitrogen nutrition. The remaining 75% of the effect have eluded explanation. We are proposing that the hydrogen released by nodules stimulates and support growth of certain soil hydrogen oxidizing bacteria.  These bacteria in return promote plant growth.  This hydrogen fertilization of soils may account for the beneficial effects of legumes on non-legume growth. The purposes of this study are to 1) analyze the soil bacterial community structure changes adjacent to nodules, 2) identify and characterize the hydrogen oxidizing bacteria in soil, 3) understanding the relationship between the hydrogen oxidizing bacteria in soils and soil fertility. The long-term goal of my research is to understand the relationship between the plant roots and soil microorganisms, especially the ones promoting the non-legume crop plants, to provide the practical protocols or inoculants for agriculture.