IF MODERN medicine cannot provide an answer to multidrug-resistant microbes, perhaps ancient animals can. Biologists have resurrected a mammalian antimicrobial compound that was last seen on Earth 59 million years ago when mammals were recovering from the Cretaceous-Tertiary extinction that wiped out the dinosaurs. Even now it is potent enough to destroy some of our most troublesome pathogens.
Ben Cocks of La Trobe University in Bundoora, Australia has resurrected an ancient gene found in a wallaby’s pouch which knocks out powerful bacteria with an almighty blow.
As marsupials, wallabies give birth to young at a much earlier stage in their development than placental mammals. For example, the tammar wallaby, Macropus eugenii, is born after 26 days, equivalent to a 6-week-old human fetus. The tiny wallabies then crawl into their mother’s pouch to grow larger.
“It’s not a clean environment,” says Cocks. Bacteria closely related to the superbugs affecting humans in hospitals have been found in the wallaby pouch. But the baby wallabies are so underdeveloped that they lack an adaptive immune system to fight them; their survival depends on their innate immune system.
Cocks’s team scoured the wallaby genome and found genes that code for 14 cathelicidin peptides, a component of the innate immune system. Lab tests revealed that many of the peptides could kill a range of multidrug-resistant pathogens – without damaging human cells.
The team noticed that genes in five of the cathelicidins were remarkably similar and probably evolved from a single ancestor. Using the changes within the five peptides, Cocks and his collaborators at the University of Sydney, Australia, worked backwards to predict the genetic sequence that codes for the original peptide. His team then used it to produce a synthetic version of the peptide, effectively resurrecting it.
It destroyed six of seven multidrug-resistant bacteria, and was 10 to 30 times more potent than modern antibiotics such as tetracycline (PLoS One, DOI: 10.1371/journal.pone.0024030).
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