An article published in the journal “Genome Biology” shows that many animals, including humans, acquired genes from microorganisms present in their environment in ancient times. This occurred through horizontal gene transfer (HGT), which transfers genetic material to cells that are not their descendants. The analysis of the genes of various species confirmed 17 genes previously identified as acquired in this way and identified another 128 in the DNA (photo ©Michael Ströck) of humans.

Horizontal gene transfer has been known for a long time especially among microorganisms. It’s been identified in primitive multicellular creatures such as nematode worms and even in insects. Only in recent years studies started to assess it among complex plants and animals.

This new research was based on the analysis of the DNA of 12 species of fruit flies (Drosophila), 4 species of nematode worms and 10 of primates, including humans. The researchers calculated the chances that their genes may have a foreign source by evaluating the alignment of the various genes similar to those in other species.

A comparison among the different groups of species allowed to estimate how long ago the genes were acquired. According to the analysis, a number of genes was acquired through horizontal gene transfer. These genes are involved in metabolism but also in the immune system.

The exam of the genes allowed to identify the origin of some of them. Previous research focused on bacteria as sources of horizontal gene transfer with negative results, so much as to create doubts that this process could take place. This new research also included viruses and even fungi as sources of genes and, also thanks to the improvement of genetic analysis techniques, gave positive and surprising results.

Most of the genes acquired in this way from primates are very ancient and happened before this order of mammals emerged. Up to 50 genes in the DNA of primates arrived from viruses. According to the authors of this research, it’s possible that there were genetic exchange among complex multicellular organisms as well, especially when there are parasitic relationships, so it’s still to be exactly assessed how common is horizontal gene transfer.

Alastair Crisp from the British University of Cambridge, lead author of the article, noted that horizontal gene transfer is far from uncommon and contributed to the evolution of many, perhaps all, animals,. The impact on the evolution of this process has yet to be assessed exactly and could help us better understand some of the mechanisms of evolution.

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