DIFFERENT PLASMIDS OF RHIZOBIUM-LEGUMINOSARUM BV PHASEOLI ARE REQUIRED FOR OPTIMAL SYMBIOTIC PERFORMANCE
DIFFERENT PLASMIDS OF RHIZOBIUM-LEGUMINOSARUM BV PHASEOLI ARE REQUIRED FOR OPTIMAL SYMBIOTIC PERFORMANCE
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DOI：
10.1128/jb.174.16.5183-5189.1992
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发表时间：
1992-08-01
影响因子：
3.2
通讯作者：
PALACIOS, R
中科院分区：
文献类型：
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作者：
BROM, S;DELOSSANTOS, AG;PALACIOS, R
豆科根瘤菌phaseoli CFN42含有6个质粒（pa ~ pf），其中pd为共生质粒。为了确定其他质粒对细胞功能的参与，我们采用正选择方案分离每个质粒的衍生物。除了一个（pe）外，所有的都得到了这些，其中只有删除的衍生物被恢复。在共生方面，我们发现除了pd之外，pb对于结瘤也是必不可少的，部分原因是存在参与脂多糖合成的基因。竞争试验揭示了pb、pc、pe和pf对菌株共生能力的正向贡献。被治愈（或因pe而被删除）的菌株的竞争力明显低于野生型。对固化菌株生长能力的分析表明，质粒参与了自由生活条件：pf-菌株无法在最小培养基上生长，而任何其他质粒固化的菌株在该培养基上的生长能力显著降低。即使在富培养基上，缺乏pb或pc或pe缺失的菌株的生长速度也比野生型低。与相应的野生型质粒互补的治愈菌株恢复了其原始表型，从而证实了所见的效果仅是由于质粒的损失。这些结果表明根瘤菌基因组在全球范围内参与了共生和自由生活功能。
Rhizobium leguminosarum bv. phaseoli CFN42 contains six plasmids (pa to pf), and pd has been shown to be the symbiotic plasmid. To determine the participation of the other plasmids in cellular functions, we used a positive selection scheme to isolate derivatives cured of each plasmid. These were obtained for all except one (pe), of which only deleted derivatives were recovered. In regard to symbiosis, we found that in addition to pd, pb is also indispensable for nodulation, partly owing to the presence of genes involved in lipopolysaccharide synthesis. The positive contribution of pb, pc, pe, and pf to the symbiotic capacity of the strain was revealed in competition experiments. The strains that were cured (or deleted for pe) were significantly less competitive than the wild type. Analysis of the growth capacity of the cured strains showed the participation of the plasmids in free-living conditions: the pf- strain was unable to grow on minimal medium, while strains cured of any other plasmid had significantly reduced growth capacity in this medium. Even on rich medium, strains lacking pb or pc or deleted for pe had a diminished growth rate compared with the wild type. Complementation of the cured strains with the corresponding wild-type plasmid restored their original phenotypes, thus confirming that the effects seen were due only to loss of plasmids. The results indicate global participation of the Rhizobium genome in symbiotic and free-living functions.