A group of small freshwater animals are protecting themselves from infections using antibiotic recipes ‘stolen’ from bacteria, according to new research by a team from the University of Oxford, the University of Stirling and the Marine Biological Laboratory (MBL), Woods Hole.
The tiny creatures are called bdelloid rotifers, which means “creeping wheel animals.” They have a head, mouth, intestines, muscles and nerves just like other animals, even though they are 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 team reports its findings this week Nature communication.
“When we translated the DNA code to see what the stolen genes were doing, we had a surprise,” said lead study author Chris Wilson of the University of Oxford. “The key genes were instructions for chemicals that we thought animals couldn’t make – they looked like recipes for antibiotics.”
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 discover that they use these genes against disease. No other animal is known to ‘steal’ genes from microbes on such a large scale.
“These complex genes – some of which are found in no other animals – were acquired from bacteria but underwent evolution in rotifers,” said co-author David Mark Welch, senior scientist and director of the Josephine Bay Paul Center. at the Marine Biological Laboratory. “This raises the potential for rotifers to produce new antimicrobial compounds that may be less toxic to animals, including humans, than the compounds we develop from bacteria and fungi.”
Self-defense recipes
Antibiotics are essential to modern healthcare, but most were not invented by scientists. Instead, they are produced naturally by fungi and bacteria in the wild, and people can create artificial versions to use as medicine.
The new study suggests that rotifers may be doing something similar.
“These strange little animals have copied the DNA that tells microbes how to make antibiotics,” Wilson explains. “We saw them use one of these genes against a disease caused by a fungus, and the animals that survived the infection produced ten times more of the chemical recipe than those that died, indicating that it helps suppress the disease.”
The scientists believe that rotifers could provide important clues in the search for drugs to treat human infections caused by bacteria or fungi.
Antibiotics become less effective because the disease-causing microbes have evolved to become resistant and no longer respond to treatment. The World Health Organization recently sounded the alarm, warning in a June report of the “urgent need” to develop new antibiotics to counter the threat of resistance.
“The recipes the rotifers use look different from known genes in microbes,” says study author Reuben Nowell of the University of Stirling. “They are just as long and complicated, but parts of the DNA code have changed. We think the recipe has changed through an evolutionary process to make new and different chemicals in the rotifers. That’s exciting because it could provide ideas for the future can suggest.” medicines.”
The genes the rotifers acquired from bacteria code for an unusual class of enzymes that join amino acids into small molecules called non-ribosomal peptides.
“The next phase of this research should include the identification of multiple non-ribosomally synthesized peptides produced by bdelloid rotifers, and establishing the conditions under which the synthesis of these compounds can be induced,” says study co-author Irina Arkhipova , senior scientist at the Marine Biological Laboratory.
A problem with developing new medicines is that many antibiotics made by bacteria and fungi are toxic or have side effects in animals. Only a few can be turned into treatments that remove harmful microbes from the human body.
If rotifers already make similar chemicals in their own cells, they could point the way to drugs that are safer to use in other animals, including humans.
Why do rotifers acquire so many foreign genes?
A big question is why rotifers are the only animals that borrow these useful genes from microbes at such high rates.
“We think it’s related to another strange fact about these rotifers,” said Tim Barraclough, co-author of the study at the University of Oxford. “Unlike other animals, we never see male rotifers. Rotifer mothers lay eggs that hatch into genetic copies of themselves, without the need for sex or fertilization.”
According to one theory, animals that copy themselves in this way can become so similar that it starts to become unhealthy. “If one person gets a disease, so will everyone else,” Barraclough explained. Because bdelloid rotifers do not have sex, which allows the parental genes to recombine in a beneficial manner, the rotifer’s mother’s genome is passed directly to her offspring without introducing any new variation.
“If rotifers don’t find a way to change their genes, they could become extinct. This could help explain why these rotifers have borrowed so many genes from other places, especially anything that helps them deal with infections,” Barraclough says.
Nowell thinks there is much more to learn from rotifers and their stolen DNA. “The rotifers used hundreds of genes not found in other animals. The antibiotic recipes are exciting, and some other genes even look like they came from The findings are part of a growing story about how and why genes are transferred between different species of life moved,” he said.
