Plants and Animals Sometimes Take Genes From Bacteria, Study Suggests

An anonymous reader quotes a report from Science Magazine: Many genome studies have shown that prokaryotes—bacteria and archaea -- liberally swap genes among species, which influences their evolution. The initial sequencing of the human genome suggested our species, too, has picked up microbial genes. But further work demonstrated that such genes found in vertebrate genomes were often contaminants introduced during sequencing. Debashish Bhattacharya, an evolutionary genomicist at Rutgers University in New Brunswick, New Jersey, and UD plant biochemist Andreas Weber took a closer look at a possible case of bacteria-to-eukaryote gene transfer that [William Martin, a biologist that concluded that there is no significant ongoing transfer of prokaryotic genes into eukaryotes, has challenged in 2015]. The initial sequencing of genomes from two species of red algae called Cyanidiophyceae had indicated that up to 6% of their DNA had a prokaryotic origin. These so-called extremophiles, which live in acidic hot springs and even inside rock, can't afford to maintain superfluous DNA. They appear to contain only genes needed for survival. 'When we find a bacterial gene, we know it has an important function or it wouldn't last' in the genome, Bhattacharya says.

He and Weber turned to a newer technology that deciphers long pieces of DNA. The 13 red algal genomes they studied contain 96 foreign genes, nearly all of them sandwiched between typical algal genes in the DNA sequenced, which makes it unlikely they were accidentally introduced in the lab. 'At the very least, this argument that [putative transferred genes are] all contamination should finally be obsolete,' says Gerald Schoenknecht, a plant physiologist at Oklahoma State University in Stillwater. The transferred genes seem to transport or detoxify heavy metals, or they help the algae extract nourishment from the environment or cope with high temperature and other stressful conditions. 'By acquiring genes from extremophile prokaryotes, these red algae have adapted to more and more extreme environments,' Schoenknecht says. While Martin says the new evidence doesn't persuade him, several insect researchers say they see evidence of such gene transfer. 'Iâ(TM)ve moved beyond asking 'if [the bacterial genes] are there,' to how they work,' says John McCutcheon, a biologist at Montana State University in Missoula who studies mealy bugs. The red algae, he adds, 'is a very clear case.'

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