A group of small, freshwater animals protect themselves from infections using antibiotic recipes “stolen” from bacteria, according to a new study. The tiny creatures are called bdelloid rotifers, which means ‘crawling wheel-animals’. They have a head, mouth, gut, muscles and nerves like other animals, though they are smaller than a hair’s breadth.
When these rotifers are exposed to fungal infection, the study found, they switch on hundreds of genes that they acquired from bacteria and other microbes. Some of these genes produce resistance weapons, such as antibiotics and other antimicrobial agents, in the rotifers. The findings were published in the journal Nature Communications.
Prior research found that rotifers have been picking up DNA from their surroundings for millions of years, but the new study is the first to discover them using these genes against diseases. No other animals are known to “steal” genes from microbes on such a large scale.
“These complex genes — some of which aren’t found in any other animals — were acquired from bacteria but have undergone evolution in rotifers,” coauthor David Mark Welch, senior scientist and director of the Josephine Bay Paul Center at the Marine Biological Laboratory says in a release. “This raises the potential that rotifers are producing 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 over twice as likely to be upregulated as other genes — a stronger enrichment than observed for abiotic stressors,” the authors write. “Among hundreds of upregulated genes, the most markedly overrepresented were clusters resembling bacterial polyketide and nonribosomal peptide synthetases that produce antibiotics. Upregulation of these clusters in a pathogen-resistant rotifer species was nearly ten times stronger than in a susceptible species.”
Most of the 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 might be doing something similar. The scientists think that rotifers could give 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 antibiotic chemicals made by bacteria and fungi are poisonous or have side-effects in animals. Only a few can be turned into treatments that clear harmful microbes from the human body. If rotifers are already making similar chemicals in their own cells, they could lead the way to drugs that are safer to use in other animals, including people.
