Horizontal gene transfer in the gut: Is it a risk?

Abstract

The human gastro-intestinal microbiota involves the highest concentration of microorganisms in the human body and contains both probiotic and pathogenic bacteria. The co-presence of these different bacteria may lead to the occurrence of the so-called horizontal gene transfer (HGT) between these microorganisms. This phenomenon has been shown to allow the transfer of genes encoding virulence traits and antimicrobial drug resistance from pathogenic bacteria to other non-pathogenic strains, which highlighted its significance to human health. It could be envisaged that HGT may occur between pathogenic and probiotic bacteria in the gut, where pathogens could receive genetic elements from probiotics that enhance the pathogen’s colonization in the gut. HGT may also allow for the acquisition of virulence genes by probiotics from neighboring gut pathogens. Pertinent literature on HGT events within gut microbiota is controversial and the present paper aims to critically address this aspect. In light of an increased production of probiotics-containing foods, addressing HGT would be a vital act to ensure food safety.