Science Weekly: Sharing genes with microorganisms

The Kansas City Star 2008 /Tribune News Service
The Kansas City Star 2008 /Tribune News Service

When you think about your genetic structure, where do you think you got your genes? A little bit of mom, a little bit of dad, but what about some help from microbe genomes?

Research published in “Genome Biology” is challenging the conventional views that genes are passed down solely through ancestors.

Horizontal Gene Transfer (HGT) is the transfer of genes between organisms living in the same environment. It is common among single-celled organisms, which is how bacteria evolves so quickly to resist antibiotics. HGT is important in the evolution of some animals, such as nematode worms which have acquired genes from microbes and plants.

The idea that HGT happens in more complex animals, such as humans has been widely debated in molecular biology. Lead author of the study from the University of Cambridge, Alastair Crisp said, “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.”

Researchers confirmed 17 genes in humans that were acquired through HGT, as well as, identified 128 additional foreign genes in the human genome.

Some of those genes were involved in lipid metabolism, including the breakdown of fatty acids and the formation of glycolipids. Others were involved in immune responses, which include inflammatory response, antimicrobial responses and immune cell signaling.

Researchers went a step beyond and were able to identify which class of organisms the genes transferred from. The most common donors in all the species that were studied were bacteria and protists. Viruses were responsible for approximately 50 or more foreign genes in primates.

Researchers in the study believe that their analysis underestimates the true extent of HGT in animals.

Currently, genome projects often remove bacterial sequences from the results because researchers assume they have been contaminated. According to the authors of the study, the potential that the bacterial sequences are a genuine part of an animal’s genome that has been acquired through HGT shouldn’t be ignored.