Ecology drives a global network of gene exchange connecting the human microbiome

Horizontal gene transfer the exchange of genetic material between different species or lineages is an important factor in bacterial evolution. A study of human microbiome data comprising more than 2,000 full bacterial genomes shows that this environment is a hotbed of horizontal gene transfer: pairs of bacteria isolated from the human body are 25-fold more likely to share transferred DNA than pairs from other environments. Thus microbial ecology rather than phylogeny or geography is the most important driver of the patterns of horizontal gene exchange. Further analysis revealed 42 unique antibiotic-resistance genes that had been transferred between human and agricultural isolates, and 43 transfers across national borders.