Abiotic Gene Transfer – A Rarity or a Ubiquity?

Abstract

Phylogenetic studies of the last two decades have revealed that horizontal gene transfer (HGT) has been playing a prominent role throughout evolution and contributed importantly to the genetic variability of species inhabiting our planet. Three main biotic mechanisms of HGT – competence for DNA uptake, conjugation, and viral transduction – have been identified and by now rather thoroughly investigated, but it is questionable whether they can account for all natural occurrences of HGT. Namely, most eukaryotes lack ability for either conjugation or competence, while transduction mostly proceeds among organisms that are phylogenetically very close to each other; yet there is mounting evidence of HGT from prokaryotes to eukaryotes, and even between eukaryotes. Here, we posit that of the four laboratory techniques most widely used for artificial genetic transformation – chemical, freeze-and-thaw, microbeads-agitation, and electroporation-based transformation – at least three have analogues in nature that can act as abiotic mechanisms of gene transfer. In particular, we show that these abiotic mechanisms of HGT, while possibly inferior in importance to biotic HGT in those organisms and environments where the latter proceeds efficiently, can also act under circumstances where this is difficult to envision for the three biotic mechanisms.