Djordjevic M A, Zurkowski W, Rolfe B G
J Bacteriol. 1982 Aug;151(2):560-8. doi: 10.1128/jb.151.2.560-568.1982.
A conjugal plasmid which encodes both peak nodulation genes and nitrogenase genes, and which is labeled with the transposon Tn5, was transferred to a wild-type Rhizobium trifolii strain to examine the stability and expression of the host range and fixation (Fix+) phenotypes. Transconjugates were isolated which were shown to initially form nitrogen-fixing nodules (Nod+ Fix+) on both clovers and peas. These hybrid strains were then repeatedly passaged through either pea or clover nodules or onto a solid agar medium to determine whether these broadened-host-range characteristics were stably maintained. An instability was noted in the capacity of some of these hybrids to form nitrogen-fixing nodules on all of the host plants used. The broadened nodulation ability was, however, more readily maintained. In some cases, the changes in the Nod+ Fix+ phenotype could be attributed to demonstrable changes in the plasmid profile of the hybrid strains, whereas in other cases no demonstrable plasmid alterations could be detected.
一种编码结瘤高峰基因和固氮酶基因且用转座子Tn5标记的接合质粒，被转移到野生型三叶草根瘤菌菌株中，以检测宿主范围和固氮（Fix+）表型的稳定性及表达情况。分离得到的接合子最初显示在三叶草和豌豆上都能形成固氮根瘤（Nod+ Fix+）。然后将这些杂交菌株反复通过豌豆或三叶草根瘤传代，或接种到固体琼脂培养基上，以确定这些拓宽的宿主范围特征是否能稳定保持。注意到其中一些杂交菌株在所有所用宿主植物上形成固氮根瘤的能力存在不稳定性。然而，拓宽的结瘤能力更容易保持。在某些情况下，Nod+ Fix+表型的变化可归因于杂交菌株质粒图谱的明显变化，而在其他情况下则未检测到明显的质粒改变。
