Small animals receive genes from bacteria that can produce antibiotics

A group of tiny freshwater animals are protecting themselves from infections using antibiotic recipes “stolen” from bacteria, a new study suggests. The tiny creatures are called bdelloid rotifers, meaning “crawling wheel animals.” They have a head, mouth, gut, muscles and nerves like other animals, despite being smaller than a hair’s breadth.

When these rotifers are exposed to a fungal infection, the study found, they switch on hundreds of genes acquired from bacteria and other microbes. Some of these genes produce weapons of resistance, such as antibiotics and other antimicrobials, in the rotifers. The findings were published in the journal Nature communication.

Previous research has shown that rotifers have been picking up DNA from their environment for millions of years, but the new study is the first to find that they use these genes to fight disease. No other animal is known to ‘steal’ genes from microbes on such a large scale.

“These complex genes — some of which are not found in other animals — were acquired from bacteria but have evolved in rotifers,” said co-author David Mark Welch, a senior scientist and director of the Josephine Bay Paul Center at the Marine Biological Laboratory, in a press release. “This raises the possibility that rotifers could produce novel antimicrobials that may be less toxic to animals, including humans, than those we develop from bacteria and fungi.”

“When rotifers were challenged with a fungal pathogen, horizontally acquired genes were more than twice as likely to be upregulated as other genes—a stronger enrichment than observed for abiotic stressors,” the authors write. “Of the hundreds of upregulated genes, clusters resembling bacterial polyketide and nonribosomal peptide synthetases that produce antibiotics were the most strikingly overrepresented. Upregulation of these clusters in a pathogen-resistant rotifer species was almost ten times stronger than in a susceptible species.”

Most antibiotics are produced naturally by fungi and bacteria in the wild, and humans can make artificial versions to use as medicine. The new study suggests that rotifers may do something similar. The scientists believe that rotifers could provide important clues in the hunt for drugs to treat human infections caused by bacteria or fungi.

One problem with developing new drugs is that many antibiotics made by bacteria and fungi are toxic or have side effects in animals. Only a few can be converted into treatments that remove harmful microbes from the human body. If rotifers already make similar chemicals in their own cells, they could pave the way for drugs that are safer to use in other animals, including humans.