Pagan J D, Scowcroft W R, Dudman W F, Gibson A H
J Bacteriol. 1977 Feb;129(2):718-23. doi: 10.1128/jb.129.2.718-723.1977.
Forty-eight mutants unable to reduce nitrate were isolated from "cowpea" Rhizobium sp. strain 32Hl and examined for nitrogenase activity in culture. All but two of the mutants had nitrogenase activity comparable with the parental sttain and two nitrogenase-defective strains showed alterations in their symbiotic properties. One strain was unable to nodulate either Macroptilium atropurpureum or Vigna uguiculata and, with the other, nodules appeared promptly, but effective nitrogen fixation was delayed. These results, and the relatively low proportion of nitrate reductase mutants with impaired nitrogenase activity, do not support the proposed commanality between nitrogenase and nitrate reductase in cowpea rhizobia. Inhibition studies of the effect of nitrate and its reduction products on the nitrogenase activity in cultured strains 32Hl and the nitrate reductase-deficient, Nif+ strains, indicated that nitrogenase activity was sensitive to nitrite rather than to nitrate.
从“豇豆”根瘤菌32H1中分离出48株不能还原硝酸盐的突变体，并检测其在培养物中的固氮酶活性。除两株突变体外，其余所有突变体的固氮酶活性均与亲本菌株相当，两株固氮酶缺陷型菌株的共生特性发生了改变。其中一株既不能与大翼豆也不能与豇豆结瘤，另一株虽然能迅速结瘤，但有效的固氮作用延迟。这些结果，以及固氮酶活性受损的硝酸盐还原酶突变体比例相对较低，并不支持豇豆根瘤菌中固氮酶和硝酸盐还原酶之间存在共同性的观点。对硝酸盐及其还原产物对培养菌株32H1和硝酸盐还原酶缺陷型、固氮基因阳性菌株固氮酶活性影响的抑制研究表明，固氮酶活性对亚硝酸盐敏感，而不是对硝酸盐敏感。
