NAD-malic enzyme affects nitrogen fixing activity of Bradyrhizobium Japonicum USDA 110 bacteroids in soybean nodules

Tan Van Dao, Mika Nomura, Rie Hamaguchi, Kensuke Kato, Manabu Itakura, Kiwamu Minamisawa, Suphawat Sinsuwongwat, Hoa Thi Phuong Le, Takakazu Kaneko, Satoshi Tabata, Shigeyuki Tajima

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14 Citations (Scopus)


The NAD+-dependent malic enzyme (DME) has been reported to play a key role supporting nitrogenase activity in bacteroids of Sinorhizobium meliloti. Genetic evidence for a similar role in Bradyrhizobium japonicum USDA110 was obtained by constructing a dme mutant. Soybean plants inoculated with a dme mutant did not show delayed nodulation, but formed small root nodules and exhibited significant nitrogen-deficiency symptoms. Nodule numbers and the acetylene reducting activity per nodule as a dry weight value 14 and 28 days after inoculation with the dme mutant were comparable to those of plants inoculated with wild-type B. japonicum. However, shoot dry weight and acetylene reducting activity per nodule decreased to ca. 30% of the values in plants with wild-type B. japonicum. The sucrose and organic acid (malate, succinate, acetate, a-ketoglutarate and lactate) contents of the nodules were investigated. Amounts of sucrose, malate and a-ketoglutarate increased on inoculation with the dme mutant, suggesting that the decreased DME and nitrogenase activities in the bacteroids resulted in a reduction in the consumption of these respiratory metabolites by the nodules. The data suggest that the DME activity of B. japonicum bacteroids plays a role in nodule metabolism and supports nitrogen fixation.

Original languageEnglish
Pages (from-to)215-220
Number of pages6
JournalMicrobes and Environments
Issue number3
Publication statusPublished - 2008


  • Bradyrhizobium japonicum
  • NAD-malic enzyme
  • Soybean nodules
  • Symbiotic nitrogen fixation


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