Paul J H, Thurmond J M, Frischer M E, Cannon J P
Department of Marine Science, University of South Florida, St Petersburg 33701.
Mol Ecol. 1992 May;1(1):37-46. doi: 10.1111/j.1365-294x.1992.tb00153.x.
Natural transformation is the mechanism of procaryotic gene transfer that involves the uptake and expression of genetic information encoded in extracellular DNA. This process has been regarded as a mechanism to transfer genes (primarily chromosomal markers) between closely related strains or species. Here we demonstrate the cell-contact-dependent transfer of a non-conjugative plasmid from a laboratory E. coli strain to a marine Vibrio species, the first report of intergeneric natural plasmid transformation involving a marine bacterium. The nucleic acid synthesis inhibitors nalidixic acid and rifampicin inhibited the ability of the E. coli to function as a donor. However, dead cells also served as efficient donors. There was an obligate requirement for cell contact. No transfer occurred in the presence of DNase I, when donors and recipients were separated by a 0.2-micron filter, or when spent medium alone was used as a source of transforming DNA. These results indicate that contact-mediated intergeneric plasmid exchange can occur in the absence of detectable viable donor cells and that small non-conjugative plasmids can be spread through heterogeneous microbial communities by a process previously not recognized, natural plasmid transformation. These findings are important in the assessment of genetic risk to the environment, particularly from wastewater treatment systems and the use of genetically engineered organisms in the environment.
自然转化是原核生物基因转移的机制，涉及摄取和表达细胞外DNA中编码的遗传信息。这一过程被视为在密切相关的菌株或物种之间转移基因（主要是染色体标记）的一种机制。在此，我们展示了非接合性质粒从实验室大肠杆菌菌株到海洋弧菌属物种的细胞接触依赖性转移，这是涉及海洋细菌的属间自然质粒转化的首次报道。核酸合成抑制剂萘啶酸和利福平抑制了大肠杆菌作为供体的功能。然而，死细胞也能作为有效的供体。细胞接触是必不可少的。当存在DNase I时、供体和受体被0.2微米的滤膜隔开时，或者仅使用用过的培养基作为转化DNA的来源时，均未发生转移。这些结果表明，在没有可检测到的存活供体细胞的情况下，接触介导的属间质粒交换也能发生，并且小型非接合性质粒可以通过一种以前未被认识的过程——自然质粒转化，在异质微生物群落中传播。这些发现对于评估对环境的遗传风险很重要，特别是来自废水处理系统以及在环境中使用基因工程生物所带来的遗传风险。
