Effects of Oxygen Concentration and Leghemoglobin on Organic Acid Degradation by Isolated Soybean Nodule Bacteriods |
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Authors: | Shigeyuki Tajima Hiroyuki Sasahara Hiroshi Kouchi Tadakatsu Yoneyama Junji Ishizuka |
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Institution: | 1. Department of Agricultural Chemistry, Kagawa University, Miki-cho, Kita-gun, Kagawa 761-07, Japan;2. The Kagawa Prefectural Fermentation &3. Foods Experimental Station Takamatsu Branch, Goutou-cho, Takamatsu 761, Japan;4. Department of Applied Physiology, National Institute of Agrobiological Resources, Kannondai, Tsukuba, Ibaraki 305, Japan |
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Abstract: | Bacteroids retaining high acetylene reduction activity (nitrogenase activity) were prepared anaerobically from soybean nodules. Addition of succinate (or of both leghemoglobin and succinate) to the acetylene reduction assay system greatly increased the activity of the isolated bacteroids.When various organic acids were incubated with the bacteroids at 2% oxygen concentration, an optimum condition for bacteroid acetylene reduction, the organic acid degradation by bacteroids was very slow, and both lactate and acetate were accumulated in the incubation system, suggesting the operation of fermentative pathway in bacteroids under such low oxygen conditions.With 20% oxygen, the added organic acids were degraded rapidly by bacteroids without addition of leghemoglobin to the incubation system.With leghemoglobin in the incubation system, the organic acid degradation by bacteroids was accelerated extensively even at 2% oxygen, and the formation of lactate and acetate were negligible. No significant difference in the organic acid degradation rate was observed between the 2% and 20% oxygen concentrations when the leghemoglobin was present in the incubation system. Addition of acetylene to the assay system slightly inhibited the organic acid degradation.This data suggests that bacteroids are unable to oxidize organic acid in low oxygen concentration and that the leghemoglobin allows the rapid organic acid dagradation by bacteroids even in such low oxygen concentrations. |
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Keywords: | nitrogen fixation nodule bacteroids leghemoglobin organic acid metabolism soybean |
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