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Primitive Microbes Stole Genes on a Surprising Scale

Horizontal gene transfer played a surprisingly large role in the evolution of primitive microbes known as Archaea, according to research published in Nature by an international collaboration.

Horizontal gene transfer is where genetic material is acquired from an unrelated organism instead of inheriting it from a direct ancestor. It is best known for its role in antibiotic resistance and its use in genetic modification technologies.

“We had known about these gene transfers for some time,” said co-author Dr David Bryant of Otago University. “What we didn’t appreciate was how they were responsible for such a huge part of microbial evolution.”

The study found that Archaea swiped dozens, and sometimes hundreds, of bacterial genes on numerous occasions. These gene transfers were a far more important mechanism of microbial evolution than had been previously thought.

The team used massive computer clusters to study the evolutionary history of the genes in higher Archaea. They compared 267,568 protein-coding genes from 134 sequenced archaeal genomes with the equivalent genes from 1847 bacterial genomes, and established their evolutionary relationships. The origins of 13 groups of higher Archaea corresponded to 2264 group-specific gene acquisitions from bacteria.

Many of the genes taken were those involved in metabolic functions. For example, several groups of Archaea whose ancestors used inorganic compounds to generate energy were able to switch to organic compounds and thus live in different environments.