Microorganisms such as bacteria enjoy swapping genes, and the trades have made a big difference in how they’ve evolved. Now new research suggests that bacteria are also easygoing about passing genes on to more complex organisms. The findings have researchers rethinking the prevalence of interspecies gene transfer and its role in evolution; they may also change the way geneticists filter out bacterial “contamination” when they sequence a new genome.
So-called lateral gene transfer is ubiquitous among bacteria–they can acquire antibiotic resistance by swapping genes with species that have evolved it–but transfers between bacteria and multicellular organisms were thought to be rare. Some of the few known cases involve genes from parasitic bacteria called Wolbachia, which infect 20% to 75% of insects, as well as other invertebrates. The parasitic bacteria live within their hosts’ cells, including the germ cells that give rise to eggs, and in past studies scientists found its genes in the genomes of two worm and insect hosts.
However, according to microbiologist Julie Dunning Hotopp of the J. Craig Venter Institute in Rockville, Maryland, common wisdom holds that these transfers are uncommon, and so genetic sequences from bacteria like Wolbachia are considered to be contamination when they’re found in insect genomes. Suspecting that their treatment as contaminants was masking transfers’ true frequency, Dunning Hotopp and her colleagues screened animal genetic databases for Wolbachia sequences. Reporting online 30 August in Science, the team found them in three wasp and four worm species. In the wasps, the DNA was a 96% match to each wasp’s resident Wolbachia strain.