This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Clostridium botulinum bacteria produce a potent neurotoxin called botulinum toxin, which causes the serious illness botulism. The toxin attacks the nervous system, leaving the body unable to control its muscles and making every breath a struggle.
Without immediate treatment, botulism can be fatal. Humans, however, have managed to domesticate this dangerous bacterium to do their bidding. Over more than 90 years, biologists have been able to turn a wild microbe into an efficient factory for medical, military and cosmetic products like Botox.
A recent study traced the genetic evolution of Army Hall A (AHA), a strain of Clostridium botulinum developed by the U.S. military in 1942. The team mapped out the DNA of more than 1,000 C. botulinum strains to find the closest living wild relatives of the domesticated AHA strain. Comparing the closest ancestors with current strains revealed more than 100 genetic differences.
The researchers identified a nonsense mutation in mutS, a DNA repair gene, that generated a hypermutator phenotype, driving AHA to accumulate point mutations ~4 times faster and small insertions/deletions ~100 times faster than wild bacteria. The findings are published in Proceedings of the National Academy of Sciences. Human interference through domestication has changed the evolutionary course of many species, from plants and bacteria to animals.
Over centuries, humans have selectively bred wild grasses to produce grains such as rice and wheat and turned wild wolves into faithful companion dogs. An unusual example of domestication is Clostridium botulinum. Once attractive to biological weapons programs because of its extreme potency, the neurotoxin it produces is now manufactured for medical and cosmetic use.
One variant called Army Hall A (AHA) was developed in a military lab and later gave rise to Hall A-hyper (HAH), a strain widely used to produce BoNT for pharmaceutical applications. Over more than 90 years of continuous growth in laboratories and industrial vessels, the strain gradually acquired distinct traits shaped by human selection, both deliberate and inadvertent. The full genetic story of how and why it transformed from a dangerous wild microbe into an efficient industrial factory remains untold.
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