RHIZOBIUM-LEGUMINOSARUM EXOPOLYSACCHARIDE MUTANTS - BIOCHEMICAL AND GENETIC ANALYSES AND SYMBIOTIC BEHAVIOR ON 3 HOSTS
RHIZOBIUM-LEGUMINOSARUM EXOPOLYSACCHARIDE MUTANTS - BIOCHEMICAL AND GENETIC ANALYSES AND SYMBIOTIC BEHAVIOR ON 3 HOSTS
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DOI：
10.1128/jb.171.9.4821-4830.1989
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发表时间：
1989-09-01
影响因子：
3.2
通讯作者：
NOEL, KD
中科院分区：
文献类型：
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作者：
DIEBOLD, R;NOEL, KD
经Tn5诱变后分离到的10株豆类根瘤菌CFN42菌株在所有供试琼脂上形成非粘液状菌落，在液体培养中不能检测到正常酸性胞外多糖的产生。突变体被分成三组。3个突变体在3.6kb碱基对的EcoRI片段上含有Tn5插入，并得到补充，使共享CFN42基因组中这种大小的EcoRI片段的宇宙具有正常的胞外多糖生产。另外5个突变体的Tn5插入片段似乎位于第二个略小的EcoRI片段上。试图用克隆的DNA来补充这第二组的突变，但没有成功。另外两个突变体的突变位于明显相邻的EcoRI片段中，这些片段携带在两个宇宙中，补充了这两个突变体。后两个突变体也缺乏含有O-抗原的脂多糖，并在菜豆植株上诱导出缺乏固氮酶活性的不发达根瘤。其他8个突变体具有正常的脂多糖和野生型对菜豆的共生能力。将每一组中的突变体分别与豆类根瘤杆菌菌株或三叶草根瘤杆菌菌株交配。Tn5突变的转移导致胞外多糖缺乏的豆类根霉生物型viciae或豆类根霉生物型三叶草的接合子在所有病例中都是共生缺陷的。这些结果支持了早先的观点，即与豌豆或三叶草的成功共生需要根瘤菌能够产生酸性胞外多糖，而与豆类的共生没有这一要求。
Ten independently generated mutants of Rhizobium leguminosarum biovar phaseoli CFN42 isolated after Tn5 mutagenesis formed nonmucoid colonies on all agar media tested and lacked detectable production of the normal acidic exopolysaccharide in liquid culture. The mutants were classified into three groups. Three mutants harbored Tn5 insertions on a 3.6-kilobase-pair EcoRI fragment and were complemented to have normal exopolysaccharide production by cosmids that shared an EcoRI fragment of this size from the CFN42 genome. The TN5 inserts of five other mutants appeared to be located on a second, slightly smaller EcoRI fragment. Attempts to complement mutants of this second group with cloned DNA were unsuccessful. The mutations of the other two mutants were located in apparently adjacent EcoRI fragments carried on two cosmids that complemented those two mutants. The latter two mutants also lacked O-antigen-containing lipopolysaccharides and induced underdeveloped nodules that lacked nitrogenase activity on bean plants. The other eight mutants had normal lipopolysaccharides and wild-types symbiotic proficiences on bean plants. Mutants in each of these groups were mated with R. leguminosarum strains that nodulated peas (R. leguminosarum biovar viciae) or clovers (R. leguminosarum biovar trifolii). Transfer of the Tn5 mutations resulted in exopolysaccharide-deficient R. leguminosarum biovar viciae or R. leguminosarum biovar trifolii transconjugants that were symbiotically deficient in all cases. These results support earlier suggestions that successful symbiosis with peas or clovers requires that rhizobia be capable of acidic exopolysaccharide production, whereas symbiosis with beans does not have this requirement.