Leclerc M C, Boemare N E
Université Montpellier II, Institut National de la Recherche Agronomique-Centre National de la Recherche Scientifique (URA no. 1184), France.
Appl Environ Microbiol. 1991 Sep;57(9):2597-601. doi: 10.1128/aem.57.9.2597-2601.1991.
Three strains of Xenorhabdus nematophilus (A24, F1, NC116) and strain Dan of Xenorhabdus bovienii were tested to evaluate whether the phase variation observed in these bacteria was in any way connected with plasmids. The plasmid patterns of both phases of A24 and F1 strains were the same, whereas the two NC116 phases had only one band each. No difference was observed between the undigested or digested plasmid patterns of the two phases from the three strains. No plasmid was detected in either phase of strain Dan. The plasmid probes were prepared from the six bands of A24 phase 1. By hybridization studies, three plasmids in two forms (open circular and supercoiled) were detected in the strain A24. Two were estimated at 12 kb, and the smallest was about 4 kb. Attempts to hybridize plasmid probes with either undigested or digested chromosomal DNA of the two phases of strain A24 were unsuccessful. The results suggest that neither a difference in plasmid content nor a plasmid recombination with the chromosome is involved in phase variation. The hybridizations revealed homologous DNA sequences among the three plasmids of strain A24 and among the plasmids of strains such as A24 and NC116, which were isolated from geographically distant countries, suggesting that plasmids may encode similar proteins.
对嗜线虫致病杆菌的三个菌株（A24、F1、NC116）以及伯氏致病杆菌的Dan菌株进行了测试，以评估在这些细菌中观察到的相变是否与质粒存在任何关联。A24和F1菌株两个相的质粒图谱相同，而NC116菌株的两个相各只有一条带。这三个菌株两个相的未消化或消化后的质粒图谱之间未观察到差异。在Dan菌株的任一相中均未检测到质粒。质粒探针由A24菌株1相的六条带制备。通过杂交研究，在A24菌株中检测到了两种形式（开环和超螺旋）的三种质粒。两种估计为12 kb，最小的约为4 kb。用A24菌株两个相的未消化或消化后的染色体DNA与质粒探针进行杂交的尝试均未成功。结果表明，相变既不涉及质粒含量的差异，也不涉及质粒与染色体的重组。杂交揭示了A24菌株的三种质粒之间以及从地理上相距遥远的国家分离出的诸如A24和NC116等菌株的质粒之间存在同源DNA序列，这表明质粒可能编码相似的蛋白质。
