Significance of newly discovered nitrogen metabolic processes in terrestrial environments

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The objective of this project was to clarify the occurrence and the mechanisms of newly discovered nitrogen metabolic processes such as ANAMMOX in terrestrial environments.1. Anaerobic ammonia oxidation (ANAMMOX): We established a highly sensitive and reproducible analytirAl method for ANAMMOX activity. The activity was found in not normal paddy soils but in a YATSU paddy soil affected by ground water rich in nitrogen. In a spring of ground water rich in nitrogen, the activity was detected. This is the first report on the occurrence of ANAMMOX in terrestrial environments.2. Anaerobic N20 production not through denitrifying process: N20 was simultaneously produced from nitrate in soil when upland soils were kept anaerobic. Soft rot bacteria may be involved in this process. We developed a method for 15N and 180-NO3 isotope concentration in water samples, nitrate of which was converted into N20 by a denitrifying bacterium, Psudomonas chlororaphos, deficit of N20 reductase, and the isotopes in N20 were measured by mass spectroscopy. By applying this method, we conducted 2-dimensional mapping of 15N-180 in nitrate in ground water and tried to clarify the origin of the nitrate.3. Nitrogen absorption by root symbiotic fungi: Root endophytic fungi, Penicillium sp. EU0013 was found to promote the growth of cabbage. The effect of growth promotion was not affected by types and amounts of nitrogen fertilization. Nitrogen transfer by arbuscular mycorrhizal (AM) fungi was examined using a newly developed root box. Under nitrogen deficit conditions, plant growth was promoted by supplying nitrogen through AM fungal hyphae. This is the first evidence that AM fungi can promote plant growth by supplying nitrogen.