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

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Root nodules of legumes have intracellular bacteria that can fix nitrogen gas into a form of nitrogen that the plant can use. Hydrogen gas is a byproduct of the nitrogen reaction, claiming about 33% of the energy that flows to the enzyme. 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. This hydrogen gas production can use up to 6% of the net 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. 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. The purposes of this study are to 1) analyze the soil bacterial community structure changes in these soil communities by T-RFLP, and characterize the "unculturable" nodule/H2-enhanced bacterial populations by screen PCR library according to the T-RFLP results; 2) culture hydrogen oxidizing bacteria from hydrogen-treated soil and the rhizosphere of HUP- nodules; 3) assay these microbes (and previously isolated microbes) for a multitude of growth-promoting traits under controlled greenhouse conditions, and finally 4) inoculate cereal crop seeds with promising bacterial strains, and assay for beneficial effects under field conditions. 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.