Abiotic Gene Transfer: Rare or Rampant?

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• 作者：Tadej Kotnik ; James C. Weaver
• 关键词：Horizontal gene transfer ; Evolution ; Freeze ; and ; thaw transformation ; Sand ; agitation transformation ; Lightning ; triggered transformation ; Electrotransformation
• 刊名：Journal of Membrane Biology
• 出版年：2016
• 出版时间：October 2016
• 年：2016
• 卷：249
• 期：5
• 页码：623-631
• 全文大小：487 KB
• 刊物类别：Biomedical and Life Sciences
• 刊物主题：Life Sciences
  Biochemistry
  Human Physiology
  
• 出版者：Springer New York
• ISSN：1432-1424
• 卷排序：249

文摘

Phylogenetic studies reveal that horizontal gene transfer (HGT) plays a prominent role in evolution and genetic variability of life. Five biotic mechanisms of HGT among prokaryotic organisms have been extensively characterized: conjugation, competence, transduction, gene transfer agent particles, and transitory fusion with recombination, but it is not known whether they can account for all natural HGT. It is even less clear how HGT could have occurred before any of these mechanisms had developed. Here, we consider contemporary conditions and experiments on microorganisms to estimate possible roles of abiotic HGT—currently and throughout evolution. Candidate mechanisms include freeze-and-thaw, microbeads-agitation, and electroporation-based transformation, and we posit that these laboratory techniques have analogues in nature acting as mechanisms of abiotic HGT: freeze-and-thaw cycles in polar waters, agitation by sand at foreshores and riverbeds, and lightning-triggered electroporation in near-surface aqueous habitats. We derive conservative order-of-magnitude estimates for rates of microorganisms subjected to freeze-and-thaw cycles, sand agitation, and lightning-triggered electroporation, at 1024, 1019, and 1017 per year, respectively. Considering the yield of viable transformants, which is by far the highest in electroporation, we argue this may still favor lightning-triggered transformation over the other two mechanisms. Electroporation-based gene transfer also appears to be the most general of these abiotic candidates, and perhaps even of all known HGT mechanisms. Future studies should provide improved estimates of gene transfer rates and cell viability, currently and in the past, but to assess the importance of abiotic HGT in nature will likely require substantial progress—also in knowledge of biotic HGT.