Soil-Plant Nutrient Research Unit, Agricultural Research Service, U.S. Department of Agriculture, Fort Collins, Colorado 80522.
Appl Environ Microbiol. 1987 May;53(5):1051-5. doi: 10.1128/aem.53.5.1051-1055.1987.
Bradyrhizobium japonicum mutants resistant to 5-methyltryptophan were isolated. Some of these mutants were found to accumulate indole-3-acetic acid (IAA) and tryptophan in culture. In greenhouse studies, nodules from control plants inoculated with wild-type bradyrhizobia contained 0.04, 0.10, and 0.58 mug of free, ester-linked, and peptidyl IAA g (fresh weight) of nodules, respectively. Nodules from plants inoculated with 5-methyltryptophan-resistant bradyrhizobia contained 0.94, 1.30, and 10.6 mug of free, ester-linked, and peptidyl IAA g (fresh weight) of nodules, respectively. This manyfold increase in nodule IAA content indicates that the Bradyrhizobium inoculum can have a considerable influence on the endogenous IAA level of the nodule. Further, these data imply that much of the IAA that accumulated in the high-IAA-containing nodules was of bacterial rather than plant origin. These high-IAA-producing 5-methyltryptophan-resistant bacteria were poor symbiotic nitrogen fixers. Plants inoculated with these bacteria had a lower nodule mass and fixed less nitrogen per gram of nodule than did plants inoculated with wild-type bacteria.
抗 5-甲基色氨酸的根瘤菌突变体被分离出来。其中一些突变体被发现可以在培养物中积累吲哚-3-乙酸（IAA）和色氨酸。在温室研究中，用野生型根瘤菌接种的对照植物的根瘤中，游离、酯结合和肽结合的 IAA 分别为 0.04、0.10 和 0.58μg（鲜重）。用 5-甲基色氨酸抗性根瘤菌接种的植物的根瘤中，游离、酯结合和肽结合的 IAA 分别为 0.94、1.30 和 10.6μg（鲜重）。根瘤中 IAA 含量的这种多倍增加表明，根瘤菌接种物可以对根瘤内源 IAA 水平产生相当大的影响。此外，这些数据表明，在富含 IAA 的根瘤中积累的大部分 IAA 来自细菌而不是植物。这些产生高 IAA 的 5-甲基色氨酸抗性细菌是低效共生固氮菌。与接种野生型细菌的植物相比，接种这些细菌的植物的根瘤质量较低，每克根瘤固定的氮也较少。
