Appl Environ Microbiol. 1995 May;61(5):2033-6. doi: 10.1128/aem.61.5.2033-2036.1995.
Several wild-type strains of Rhizobium meliloti isolated from alfalfa nodules exhibited different plasmid profiles, yet did not differ in growth rate in yeast-mannitol medium, utilization of 43 different carbon sources, intrinsic resistance to 14 antibiotics, or detection of 16 enzyme activities. In contrast, three measures of effectiveness in symbiotic nitrogen fixation with alfalfa (shoot length, dry weight, and nitrogen content) indicated that R. meliloti SAF22, whose plasmid profile differs from those of the other strains tested, is significantly less effective than other wild-type strains in symbiotic nitrogen fixation. Light microscopy of nodules infected with strain SAF22 showed an abnormal center of nitrogen fixation zone III, with bacteria occupying a smaller portion of the infected host cells and vacuoles occupying a significantly larger portion of adjacent uninfected host cells. In contrast, the effective nodules infected with other wild types or plasmid pRmSAF22c-cured segregants of SAF22 did not display this cytological abnormality.
从紫花苜蓿根瘤中分离出的几种野生型根瘤菌 meliloti 菌株表现出不同的质粒图谱，但在酵母甘露醇培养基中的生长速度、对 43 种不同碳源的利用、对 14 种抗生素的固有抗性或检测到的 16 种酶活性方面没有差异。相比之下，与紫花苜蓿共生固氮的三种有效性测量（茎长、干重和氮含量）表明，质粒图谱与其他测试菌株不同的 R. meliloti SAF22 在共生固氮中的有效性明显低于其他野生型菌株。用 SAF22 菌株感染的根瘤的光学显微镜观察显示，氮固定区 III 的中心异常，细菌占据感染宿主细胞的较小部分，液泡占据相邻未感染宿主细胞的显著更大部分。相比之下，用其他野生型菌株或质粒 pRmSAF22c 治愈的 SAF22 分离株感染的有效根瘤没有显示这种细胞学异常。
