News in Science

Water creatures caught stealing DNA

Tiny freshwater organisms that have a sex-free lifestyle, may have survived so well because they steal genes from other creatures, US scientists report.

Researchers from the Harvard University in Cambridge, Massachusetts, have found genes from bacteria, fungi and even plants incorporated into the DNA of bdelloid rotifers - minuscule animals that appear to have given up sex 40 million years ago.

Their report appears in this week's edition of Science.

Sex is used by most life forms as a way of coping with changing circumstances, by allowing organisms to develop useful new genes and ditch harmful, mutated ones.

The resilience of bdelloid and their sex-free lifestyle has stumped scientists.

The team, headed by Professor Matthew Meselson, looked at the DNA of bdelloid rotifers to see how they manage to survive and evolve.

It appears they overcome this hurdle by stealing DNA from our organisms.

"Our result shows that genes can enter the genomes of bdelloids in a manner fundamentally different from that which, in other animals, results from the mating of males and females," says Meselson.

"We found many genes that appear to have originated in bacteria, fungi, and plants."

Resilient creatures

The translucent, waterborne creatures, which range in size from 0.1 to 1 millimetres long, lay eggs, but all their offspring are female.

The researchers believe that when bdelloids dry out, they fracture their genetic material and rupture cellular membranes. When they rehydrate, they rebuild their genomes and their membranes, incorporating shreds of genetic material from other bdelloids and unrelated species in their vicinity.

"These fascinating animals not only have relaxed the barriers to incorporation of foreign genetic material, but, more surprisingly, they even managed to keep some of these alien genes functional," report co-author Dr Irina Arkhipova says.

According to the researchers, the next step is to determine whether bdelloid genomes also contain homologous genes imported from other bdelloids.

Meselson and his colleagues also hope to examine whether the animals actually use any of the hundreds of snippets of foreign DNA they appear to vacuum up.

Understanding how the animals acquire and make use of these new genes could have implications for medicine.

Genetic mutations, which occur constantly in any living organism, underlie cancer, heart disease and various other diseases.