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Genes from bacteria, viruses, fungi found in human genome

Saturday, 14 March 2015 10:39 PM [ Last Update: Saturday, 14 March 2015 11:55 PM ]

Abstract illustration depicting DNA (file photo courtesy of agsandrew / Fotolia)

The genome of humans and other complex animals contains essential “foreign” segments of genetic code, new study says.

The research, which cast doubt on the theory that evolution is exclusively a process of selection through ancestry, was published on Friday in the journal Genome Biology.

Initially, it was thought that complex animals' genes were solely inherited through parents, but the study proposes that horizontal gene transfer (HGT) is still ongoing between microorganisms and more complicated creatures.

“This is the first study to show how widely horizontal gene transfer (HGT) occurs in animals, including humans, giving rise to tens or hundreds of active 'foreign' genes. Surprisingly, far from being a rare occurrence, it appears that HGT has contributed to the evolution of many, perhaps all, animals and that the process is ongoing, meaning that we may need to re-evaluate how we think about evolution," said Lead author Alastair Crisp from the University of Cambridge.

During HGT, genes from various organisms living in the same environment are transferred to others through the process, which is widely carried out between single-celled life forms such as bacteria or algae and is thought to hold a key role in phenomena such as bacterial resistance to antibiotics.

During the research, the genomes of 12 fruit fly species, four nematode worm species, and ten species of primate, including humans, were analyzed and then the results were compared to find similarities to discover the likeliness of a certain gene acquired via HGT and how long ago this occurred.

The research unveiled 128 new foreign genes and confirmed that 17 formerly reported ones were acquired through HGT from bacteria, viruses and fungi in humans. Some of which have key roles in the human genome, such as in metabolism and digestion, and the immune responses.

"This means that the tree of life isn't the stereotypical tree with perfectly branching lineages. In reality, it's more like one of those Amazonian strangler figs where the roots are all tangled and crossing back across each other," Crisp added .

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Alastair Crisp