Horizontal Gene Transfer May Be More Prevalent in Closely Related Bacterial and Microbial Species

Abstract

Increasing prevalence of antibiotic resistance in microbes has been attributed to horizontal gene transfer. But, in order for horizontal gene transfer to be effective, the genes transferred must be expressed, and this requires the concomitant transfer of suitable promoter and ribosome binding site. Biotechnology and molecular biology studies have determined there is species-specificity in promoter and ribosome binding sites in microbes, and this may be interpreted as a species barrier. Hence, promoter from one distantly related species may not be recognized by the RNA polymerase of another species. This then suggests that the phenomenon of successful horizontal gene transfer may be between closely related microbial species sharing homology in promoter and ribosome binding site sequence. The match between the transferred promoter and the endogenous RNA polymerase may only be 50 to 60%, but this should be sufficient for some leaky expression where sufficient protein and enzymes confer a fitness advantage to the species. While leaky expression likely conferred a small fitness advantage, but this selective advantage likely potentiated an evolutionary trajectory where the transferred promoter and ribosome binding site be moulded to be similar to endogenous variants. This facet then precludes detection by modern DNA sequencing approaches as our current methodologies do not observe evolution in action. Overall, horizontal gene transfer is as-yet assumed to transfer DNA across different species. But this may not be true as promoter and ribosome binding sites represents species barriers hard to surmount. Hence, horizontal gene transfer may be more feasible between closely-related microbial species.

Keywords: horizontal gene transfer, closely-related species, promoter sequence, ribosome binding site sequence, evolution,