Heinemann J A, Ankenbauer R G
NIH, NIAID, LMSF, Rocky Mountain Laboratories, Hamilton, Montana 59840.
Mol Microbiol. 1993 Oct;10(1):57-62. doi: 10.1111/j.1365-2958.1993.tb00903.x.
Gene transfer between organisms is a prime contributor to evolution. Bacterial conjugation is probably the most important mechanism by which genes are spread among prokaryotes and perhaps also contributes to eukaryotic evolution. Conjugation is mediated by plasmids. The mechanism of conjugation remains ill-understood despite progress in the identification, mapping and sequencing of genes required for plasmid transmission. All conjugation-specific genes (those required only for DNA transfer and establishment) identified to date map to plasmids. We found that IncP plasmids could enter and subsequently convert maxicells, which are trapped in a metabolic state that prevents de novo expression of chromosomal genes, into conjugative donors. This suggests that IncP plasmids encode not only necessary functions but indeed all functions specific to DNA transmission. Thus, like viruses, plasmids can convert non-viable cells into gene vectors.
生物体之间的基因转移是进化的主要推动因素。细菌接合可能是基因在原核生物中传播的最重要机制，或许也对真核生物的进化有贡献。接合由质粒介导。尽管在质粒传递所需基因的鉴定、定位和测序方面取得了进展，但接合机制仍未得到充分理解。迄今为止鉴定出的所有接合特异性基因（即仅用于DNA转移和建立所需的基因）都定位于质粒上。我们发现，IncP质粒可以进入并随后将处于代谢状态而阻止染色体基因从头表达的大细胞转化为接合供体。这表明IncP质粒不仅编码必要功能，实际上还编码DNA传递的所有特异性功能。因此，与病毒一样，质粒可以将无活力的细胞转化为基因载体。
