WOODS HOLE, Mass. ɫƵ A group of small, freshwater animals protect themselves from infections using antibiotic recipes ɫƵstolenɫƵ 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 ɫƵcrawling wheel-animals.ɫƵ They have a head, mouth, gut, muscles and nerves like other animals, though they are about a human hair's width in size.
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 team reports its findings this week in
ɫƵWhen we translated the DNA code to see what the stolen genes were doing, we had a surprise,ɫƵ said lead study author of University of Oxford. ɫƵThe main genes were instructions for chemicals that we didnɫƵt think animals could make ɫƵ they looked like recipes for antibiotics.ɫƵ
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 ɫƵstealɫƵ genes from microbes on such a large scale.
ɫƵThese complex genes ɫƵ some of which arenɫƵt found in any other animals ɫƵ were acquired from bacteria but have undergone evolution in rotifers,ɫƵ said study co-author David Mark Welch, senior scientist and director of the Josephine Bay Paul Center at the Marine Biological Laboratory. ɫƵThis 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.ɫƵ
Like other animals, rotifers need strategies to fight off infections and avoid ending up like this diseased individual, which has been taken over and killed by a fungus. Credit: C. G. Wilson
Recipes for self-defense
Antibiotics are essential to modern healthcare, but most of them were not invented by scientists. Instead, they 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.
ɫƵThese strange little animals have copied the DNA that tells microbes how to make antibiotics,ɫƵ explains Wilson. ɫƵWe watched them using one of these genes against a disease caused by a fungus, and the animals that survived the infection were producing 10 times more of the chemical recipe than the ones that died, indicating that it helps to suppress the disease.ɫƵ
The scientists think that rotifers could give important clues in the hunt for drugs to treat human infections caused by bacteria or fungi.
Antibiotics are becoming 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, of the ɫƵpressing needɫƵ to develop new antibiotics to counter the threat of resistance.
ɫƵThe recipes the rotifers are using look different from known genes in microbes,ɫƵ said study author of the University of Stirling. ɫƵTheyɫƵre just as long and complicated, but parts of the DNA code have changed. We think the recipe has been altered by a process of evolution to make new and different chemicals in the rotifers. ThatɫƵs exciting because it might suggest ideas for future medicines.
This rotifer has just survived a life-threatening infection. When a fungal disease attacked, she switched on hundreds of genes that her ancestors copied from microbes, including antibiotic recipes stolen from bacteria. Credit: C.G. Wilson, 2019
The genes the rotifers acquired from bacteria encode an unusual class of enzymes that assemble amino acids into small molecules called non-ribosomal peptides.
ɫƵThe next phase of this research should involve identification of multiple non-ribosomally synthesized peptides produced by bdelloid rotifers, and establishment of the conditions upon which the synthesis of these compounds can be induced,ɫƵ said study co-author Irina Arkhipova, senior scientist at the Marine Biological Laboratory.
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.
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.
ɫƵWe think it might be linked with another strange fact about these rotifers,ɫƵ said , a study co-author from the University of Oxford. ɫƵUnlike other animals, we never see male rotifers. Rotifer mothers lay eggs that hatch into genetic copies of themselves, without needing sex or fertilization.ɫƵ
According to one theory, animals that copy themselves like this can become so similar that it starts to be unhealthy. ɫƵIf one catches a disease, so will the rest,ɫƵ explained Barraclough. Because bdelloid rotifers donɫƵt have sex, which allows the parental genes to recombine in beneficial ways, the rotifer motherɫƵs genome is directly transferred to her offspring without introducing any new variation.
These rotifers are crawling around next to a single human hair that has been added to their dish to show the scale. They have laid several small oval-shaped eggs, which will hatch into genetic clones of their mother. Credit: C.G. Wilson, 2024
ɫƵIf rotifers donɫƵt find a way to change their genes, they could go extinct. This might help explain why these rotifers have borrowed so many genes from other places, especially anything that helps them cope with infections,ɫƵ said Barraclough.
Nowell thinks there is much more to learn from rotifers and their stolen DNA ɫƵThe rotifers were using hundreds of genes that arenɫƵt seen in other animals. The antibiotic recipes are exciting, and some other genes even look like theyɫƵve been taken from plants. The findings are part of a growing story about how and why genes get moved between different kinds of life,ɫƵ he said.
Video Credit: Emily Greenhalgh, MBL
Citation:
Reuben W. Nowell, Fernando Rodriguez, Bette J. Hecox-Lea, David B. Mark Welch, Irina Arkhipova, Timothy G. Barraclough, and Christopher G. Wilson (2024) Bdelloid rotifers deploy horizontally acquired biosynthetic genes against a fungal pathogen, Nature Communications: DOI: .
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