Chien C T, Maundu J, Cavaness J, Dandurand L M, Orser C S
Department of Bacteriology and Biochemistry, University of Idaho, Moscow 83843.
FEMS Microbiol Lett. 1992 Jan 1;69(2):135-40. doi: 10.1016/0378-1097(92)90617-w.
Spontaneous mutants of Rhizobium leguminosarum biovar viciae strain C1204b were selected for their ability to tolerate 0.2 M NaCl, a growth-inhibiting level of salt for the parental strain. Transposon-mediated salt-sensitive mutants of strain C1204b were screened for their inability to grow in 0.08 M NaCl. Quantitation of the free-amino acid pools in the mutants grown in NaCl revealed a dramatic increase in glutamine, serine, glutamate and proline, and to a lesser extent alanine and glycine in the salt-tolerant mutants in comparison with the parental strain exposed to NaCl; but only glutamate and proline increased in the salt-sensitive mutants under NaCl stress. Extracellular polysaccharide levels were quantitated for the salt-tolerant mutants and determined to be approximately two-fold higher than for the parental strain. Although the mutations that occurred in the NaCl-tolerant and NaCl-sensitive strains did not interfere with nodule formation, no nitrogenase activity could be observed in the NaCl tolerant mutants as evaluated by acetylene reduction.
豌豆根瘤菌生物变种C1204b的自发突变体因其耐受0.2M NaCl的能力而被筛选出来，该盐浓度对亲本菌株具有生长抑制作用。通过转座子介导筛选出C1204b菌株的盐敏感突变体，这些突变体在0.08M NaCl中无法生长。对在NaCl中生长的突变体的游离氨基酸库进行定量分析，结果显示，与暴露于NaCl的亲本菌株相比，耐盐突变体中的谷氨酰胺、丝氨酸、谷氨酸和脯氨酸显著增加，丙氨酸和甘氨酸也有一定程度的增加；但在NaCl胁迫下，盐敏感突变体中只有谷氨酸和脯氨酸增加。对耐盐突变体的胞外多糖水平进行定量分析，结果表明其水平约为亲本菌株的两倍。尽管耐NaCl和盐敏感菌株中发生的突变不影响根瘤形成，但通过乙炔还原法评估发现，耐NaCl突变体中未观察到固氮酶活性。
