The human microbiome: a hot spot of microbial horizontal gene transfer.

The human body harbors numerous microbes, and here exists a close relationship between microbes and human health. The Human Microbiome Project has generated whole genome sequences of several hundred human microbes. In this study, we identified horizontal gene transfer (HGT) events in human microbes and tried to elucidate the relationships between the gene-transferring microbes. A total of 13,514 high confidence HGT genes were identified in 308 human microbes. The horizontally transferred genes were enriched for Gene Ontology terms pertaining to catalytic functions and metabolic processes. Construction of an HGT event network suggested that the human microbes could be divided into specific communities which only partly overlap their distribution in human body. Our research suggests that human microbiome may facilitate frequent horizontal gene transfer among bacteria in human body. Awareness of HGT in human microbiome may aid our understanding of the relationship between the human microbiome and human health.