Small animals use ‘stolen’ genes from bacteria to protect themselves from infection, study shows

According to new research by a team from the University of Oxford, the University of Stirling and the Marine Biological Laboratory (MBL), Woods Hole, certain small freshwater animals protect themselves from infection by using antibiotic recipes ‘stolen’ by bacteria.

The tiny creatures are called bdelloid rotifers, which means “crawling wheeled animals.” They have heads, mouths, intestines, muscles and nerves like other animals, even though they are smaller than a hair.

The study found that when these rotifers are exposed to a fungal infection, they turn on hundreds of genes they acquired from bacteria and other microbes. Some of these genes produce weapons of resistance in rotifers, such as antibiotics and other antimicrobials. The team reports its findings in The nature of communication.

“When we translated the DNA code to see what the stolen genes were doing, we were in for a surprise,” said study lead author Chris Wilson of the University of Oxford. “The master genes were instructions for chemicals we didn’t think animals could make – they looked like prescriptions for antibiotics.”

Previous research has found that rotifers have been acquiring DNA from their surroundings for millions of years, but the new study is the first to find them using these disease-fighting genes. 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 any other animals – were acquired from bacteria but evolved in rotifers,” said study co-author David Mark Welch, principal scientist and director of the Josephine Bay Paul Center at the Marine Biology Laboratory. “This raises the potential for rotifers to produce new antimicrobials that may be less toxic to animals, including humans, than those we develop from bacteria and fungi.”

Recipes for self-defense

Antibiotics are essential to modern healthcare, but most of them were not invented by scientists. Instead, they are naturally produced by fungi and bacteria in the wild, and humans can make man-made versions that can be used as medicine.

A new study suggests that rotifers might do something similar.

“These strange little animals have copied the DNA that tells microbes how to make antibiotics,” explains Wilson. “We watched them use one of these genes against a disease caused by a fungus, and the animals that survived the infection produced 10 times more of the chemical recipe than the ones that died, suggesting that it helps suppress the disease.”

Scientists believe that rotifers could provide important clues in the search for drugs to treat human infections caused by bacteria or fungi.

Antibiotics are becoming less effective as disease-causing microbes have evolved to become resistant and unresponsive to treatment. The World Health Organization recently sounded the alarm, warning in a June report of an “urgent need” to develop new antibiotics to counter the threat of resistance.

“The recipes that rotifers use look different from known genes in microbes,” said study author Reuben Nowell of the University of Stirling. “They are the same length and complexity, but parts of the DNA code have changed. We think the recipe has been altered by the process of evolution to make new and different chemicals in rotifers. This is exciting because it may suggest ideas for the future.” medicines.”

The genes that rotifers acquired from bacteria encode an unusual class of enzymes that fold amino acids into small molecules called non-ribosomal peptides.

“The next phase of this research should include identifying more non-ribosomally synthesized peptides produced by bdelloid rotifers and determining the conditions under which the synthesis of these compounds can be induced,” said study co-author Irina Arkhipova, senior scientist at the Marine Biology Laboratory.

One of the challenges in developing new drugs is that many chemical antibiotics produced by bacteria and fungi are poisonous or cause side effects in animals. Only a few of these can be turned into treatments that eliminate harmful microbes from the human body.

If rotifers already produce similar chemicals in their own cells, it could lead to drugs that are safer to use in other animals, including humans.

Why do rotifers acquire so many foreign genes?

The big question is why rotifers are the only animals that borrow these useful genes from microbes at such high rates.

“We think this might be related to another strange fact about these rotifers,” said Tim Barraclough, co-author of the study from the University of Oxford. “Unlike other animals, we never see male rotifers. Mother rotifers 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 they become unhealthy.

“If one gets sick, the rest will catch it,” Barraclough explained. Because bdelloid rotifers are sexless, allowing parental genes to recombine in beneficial ways, the genome of a rotifer mother is directly passed on 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 cope with infections,” Barraclough said.

Nowell thinks there is much more to be learned from rotifers and their stolen DNA.

“Rotifers used hundreds of genes not seen in other animals. The recipes for antibiotics are exciting, and some other genes even look like they were taken from plants. The findings are part of a growing story about how and why genes move between different kinds of life ,” he said.