수종의 두과작물과 수도에서 분리한 Rhizobium 및 Azospirillum들의 내염성을 조사하고 salt stress에 의하여 유도되는 균주의 생리적 특성 및 식물이나 미생물에서 osmoprotectant 로 작용하는 proline, glycine betaine 및 glutamate가 질소고정균의 생육이나 질소고정력에 미치는 영향을 연구하였다. 분리된 대부분의 질소고정균들은 0.6 M NaCl 농도에서 생육이 현저히 감소되었지만 Acacia rhizobia sp86 은 1.4 M NaCl 농도에서도 생육이 가능하였다. Osmotic stress에 의하여 증가되는 intracellular 유리아미노산은 Rhizobium 및 Azospirillum에서 glutamate 였으며, 특히 Acacia rhizobia sp86은 salt stress에 의하여 5배정도 glutamate를 축적하였다. Osmoprotectant (proline, glycine betaine, glutamate)를 배지내에 1 mM 첨가함으로서 salt stress에 의하여 감소되는 질소고정균의 생육과 질소고정력을 방지하였으며, glycine betaine이 가장 효과적이었다.
The Rhizobium and Azospirillum spp. were isolated from the root nodules of several leguminous plants and rhizosphere of various paddy rice varieties. The growth of the nitrogen-fixing strains isolated was largely inhibited in yeast extract-mannitol medium (AMA) containing 0.6 M NaCl. In response to osmotic stress, the nitrogen-fixing strains accumulate intracellular free glutamate. The growth and nitrogenase activity of Rhizobium and Azospirillum were increased by addition of osmoprotectants such as proline, glycine betaine, and glutamate during salt stress. Glycine betaine was the most effective among exogenous osmoprotectants tested. In the absence of sodium chloride, nitrogenase activity seem to be slightly decreased by the presence of the proline or glycine betaine. These results revealed that nitrogenase activity was repressed by fixed nitrogens such as proline or glycine betaine.
