Are Bacterial Genes in Humans the Result of Lateral Transfer?

Lateral gene transfer is a fascinating concept which necessitates a discussion on the possibility of the transfer of genetic information between distantly related species. This phenomenon is quite surprisingly seen in two of the most interesting species: humans and bacteria; such a possibility is further explored in Steven Salzberg and his team’s research paper. The aim of this paper is to focus on gathering evidence to show that genes were laterally transferred from the prokaryotic genome (bacteria) to the eukaryotic genome (humans), as a reason behind the presence of bacterial genes in humans.

Salzberg and his team used the method of elimination to determine cases of lateral transfer between bacteria and humans: this method involved considering only those genes shared by bacteria and humans. They had a large and a highly comprehensive data set of genomes for analysis, which was beneficial for their research because a larger sample size leads to greater accuracy.

However, they observed something quite different: adding more non-vertebrate genomes to their sample resulted in the number of lateral transfer cases decreasing throughout the analysis. And from this observation, it was quite clear that lateral transfer was not a plausible explanation for the sharing of genes between bacteria and humans. A myriad of interesting factors including evolutionary rate variation, small sample of non-vertebrate genomes, and gene loss; these can be considered more plausible explanations in comparison to lateral gene transfer.

In conclusion, the methods and data they used for analysis were not sufficient or thorough enough to prove that lateral gene transfer is indeed a deterministic process for transfer of genetic information between distantly related species.

Reference: Salzberg, S. L., White, O., Peterson, J., & Eisen, J. A. (2001). Microbial genes in the human genome: Lateral transfer or gene loss? Science, 292(5523), 1903-1906. https://doi.org/10.1126/science.1061036