高温胁迫对根瘤菌Tn5在土壤中的存活及其表型表达的影响

研究了３株弗氏中华根瘤菌（Ｒｈｉｚｏｂｉｕｍｆｒｅｄｉｉ）Ｔｎｓ突变株于适宜温度和高温胁迫两种条件下在土壤中的存活和Ｔｎｓ表型的表达．在适宜温度（２８℃）条件下的灭菌和未灭菌土壤中的存活研究表明生物因素抑制了突变株和野生型的生长．但野生型和突变株的存活种群密度之间无显著差异（Ｐ＝０．０１）．在高温胁迫（４０℃）条件下，土壤中野生型和突变株的种群密度迅速下降，其中部分ＯＮ－２和ＯＮ－３细胞丢失了Ｔｎｓ表型，说明部分细菌的Ｔｎ５表型在高温胁迫条件下不能表达．

Impact of high temperature stress on survival of Tn5 mutants or Rhizobium fredii and phenotypic expression of Tn5 in soil

A wild type and thyee transposon Tn5 insertion mutants of Rhizobium fredii were used to study their survival and Tns phenotypic expression in soil under optimum temperature (28 C)and temperature stress (40 C). Survival studies with sterile and nonsterile soils show that under optimum temperature (28 C), biotic factors inhibit the growth of mutant and wild type. But, there is no significant difference (P=0. 01) between the surviving populations of wild type and Tn5 mutants. Under temperature stressed condition (40 C), both wild type and mutant populations decline rapidly, and some of the mutant cells (ON-2 and ON-3) can't express kanamycin resistance. These results suggest that high temperature is a harmful factor for the survival of bacteria and the phenotypic expression of Tn5 in soil.