Worried about bioterror? Step back from the ledge.

Nature, as it turns out, remains a much more potent threat than anything a would-be bioterrorist might throw at us.

That’s the message from a fine article in Slate written by Carl Zimmer, who documents the efforts of scientists who dug into the 2006 E. coli outbreaks carried by spinach and lettuce.


E. Coli: The ultimate diet drug?

The same strain of E. Coli (O157:H7) was behind both outbreaks. But scientists became especially concerned as three to four times as many people were taken violently ill during the outbreaks as one would normally expect from the O157:H7 strain. What was happening?

To answer the question Michigan State University scientists sequenced the entire genome of a microbe taken from the 2006 spinach outbreak. Here’s Zimmer:

They discovered that it is not a minor variation on the basic E. coli O157:H7 plan. It is a major overhaul. Hundreds of its genes can’t be found in other strains. It has lost hundreds of others. And many of the genes it shares with its close relatives have mutated.

The scientists concluded that at some point in the not-too-distant past, this strain of E. coli O157:H7 evolved rapidly into a far meaner pathogen than its ancestors. Natural selection altered its genes quickly, thanks to the ability bacteria have to reproduce in as little time as 20 minutes. Speeding up their evolution even further was their ability to take in DNA from other microbes, even from species that are only distantly related. The genomes of bacteria are being continually rejiggered into new combinations of genes. Some bacteria become better at capturing sunlight, others at resisting antibiotics. And, in the case of the spinach strain of E. coli O157:H7, the introduction of viral DNA has made them far nastier.

It is chilling to think just how quickly a new, more dangerous form of E. coli has emerged — and it’s tempting to think that its quick arrival bodes ill for synthetic biology. After all, if it just takes a few years for a dangerous strain to evolve in the wild, just think how easy it will be for people to build them in the lab.

In fact, the spinach outbreak teaches a very different lesson. The Michigan State scientists have no idea what is making the new strain so mean. It’s a straightforward task to identify the hundreds of new genes in its genome, but the researchers can’t say precisely what all those new genes are doing. The same goes for the hundreds of missing genes as well as for the other genes tweaked and fine-tuned by natural selection.

In other words, our mastery of the natural world remains far, far from complete. Zimmer adds:

Inventors don’t always design their inventions from scratch, though. Perhaps someone could create a new pathogen simply by mimicking nature: combining different sets of genes, mutating a few of them, and using trial and error to find ones that worked? Probably not. Nature’s lab bench is colossal. Millions of cattle and other animals are carrying around E. coli O157:H7, and an incalculable number of viruses are invading them, trying out new combinations. Many of those combinations turn out to be failures, but natural selection can give rise to a few spectacular successes. Even if a government built a giant lab just for the purpose of stumbling across a new pathogen, it might take centuries or millenniums to hit on something like the spinach strain.

All of this, course, doesn’t mean a terrorist might figure out a lethal, efficient way to disperse a nasty, nature-made bioweapon.

Found via 3QuarksDaily.

Categories: Biology, Genetics
Eric Berger