中文摘要：

为了考察热处理后的重组DNA进入水环境后可能存在的环境风险，以pET-28b质粒为材料，以质粒相对转化效率为指标，考察了热变性重组质粒DNA的复性可能性，并在此基础上构建了人工模拟水环境系统，研究了热变性质粒DNA在水环境中的降解速率和影响因素．结果表明，热变性pET-28b质粒经过30rain后，其转移活性可以得到恢复，在4～37％之间，温度越高越有利于热变性质粒的复性．热处理过程中未被降解的质粒DNA进入水环境后，在pH值为7、8时降解速率相对较慢，在pH值为5、6、9的条件下，降解较快，但在任何pH下，1．0h后仍存在未降解的质粒DNA．水环境中的NaCl对热处理质粒DNA有一定的保护作用，而且这种作用是随着NaCl质量分数的提高而增强．进入水环境中的热变性DNA有足够的时间复性，从而可能发生基因转移．因此，这些热处理的质粒DNA进入环境后理论上存在一定的生态风险．

英文摘要：

Plasmid pET-28b was used as a test plasmid to investigate the potential environmental risk caused by thermo-treated recombinant DNA. Firstly, plasmid DNA transformation was performed to evaluate the re-naturation efficiency of the thermo-treated plasmid DNA, and then simulated aquatic environments were constructed to determine the persistence of un-decayed plasmid DNAs in the aquatic environment after thermo-treatment. The results showed that the transforming activity of the thermo-treated plasmid DNA could be recovered to a certain extent after re-naturing for 30 min. From 4 - 37℃, the higher the temperature, the more transforming activity of denatured plasmid DNA will be recovered. When thermo-treated plasmid DNAs were discharged into simulated aquatic environments with pH from 5 - 9, the persistence of un-decayed plasmid DNAs at pH 7 and 8 exceeded those at 5, 6 or 9, but at any pH some could persist for 1.0 h or more. Higher ionic strengths further inhibited decay of the recombinant plasmid in the simulated aquatic environment. These results indicate that recombinant DNAs which are not destroyed during the thermo-treatment process cannot be degraded completely in a short time in the aquatic environment, which means when they are discharged into aquatic environment, they may have enough time to re-nature and transform, thus resulting in gene diffusion.