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How To Catch An Anthrax Killer

ALEX CHADWICK, host

Trying to track down the anthrax killer, the FBI investigators needed to create new science in bacteriology. For more, we turn to NPR's David Kestenbaum, who's with NPR's science desk. David, FBI sources are quoted as saying that their scientists literally were inventing science, microbial forensics. What is that? Why was it necessary?

DAVID KESTENBAUM: Well, when the anthrax showed up in the mail, we didn't even have a full sequence of the anthrax genome to start with. You know, just sequencing technology has come a long way. The stuff we can do now, you can sequence a whole genome in a very short period of time, and, you know, it was a much longer effort in the past.

So their first analysis was, they looked at the DNA in spores, and they found, hey, this is the Ames strain. But it turns out the Ames strain of anthrax was in a number of labs, so that wasn't so helpful. So they had to look even closer. And what they found is that, in the spores that were in the letters, they weren't all exactly the same kind of spores. There was some small mixture of a couple of other types in there at a low level, and they were able to match that with the sample of anthrax bacteria at Fort Detrick.

CHADWICK: So they're looking at the genetic makeup of the particular anthrax bacteria that they'd found, and what is?

KESTENBAUM: Think of it this way. So, I mean, if you had a bucket of rice, right?

CHADWICK: Yeah.

KESTENBAUM: And they're mostly white grains of rice. But in there, there are a few ones that are brown, and you know that a certain country tends to produce that mixture. Well, then you'd say I have some confidence this rice came from that country. It's like that, except that the ones that are a different color, they're not that easy to tell. You have to actually look into their genome along the many, many, many chemical letters, and you'll find a slight, slight difference. So it's very difficult.

CHADWICK: So what is it that these scientists were doing? What were they creating along the way to try to solve the mystery of who had perpetrated this crime?

KESTENBAUM: Well, they were trying to figure out where the anthrax had come from, right? I mean, it would be nice if you could narrow it to a particular lab. And for this, they were able to show that it matched the stuff at this lab.

CHADWICK: Well, can they figure out when these spores were made?

KESTENBAUM: Yeah, there was actually some really interesting science done fairly early on, where they carbon dated the spores. You know, you hear about carbon dating for looking at dinosaur bones, but you tend to think of millions of years, right?

They were able to narrow it to within about a couple of years, and this is due to some strange fact that, when we did all the above ground atomic nuclear tests, we put a certain isotope of carbon in the air. And that makes it into the water that was used to grow the spores. And the amount of carbon in the air started declining over the years, since we stopped the testing.

So by using that, you can kind of figure out when the spores were made. It's actually been used to tell whether someone who - someone has a stuffed endangered species, whether that was killed before they became endangered or whether maybe it was killed in a time when it would have been illegal.

CHADWICK: I've read statements from the FBI. They're clearly very excited about what they've managed to do scientifically in labs to figure this out, but as a science reporter, is this proof?

KESTENBAUM: It's not. I mean what - it would be very interesting to see how this played out in a court of law, and unfortunately, it does not look like it will.

Microbial forensic has just not - it hasn't appeared in court. DNA finger prints are one thing, you know. If the cops find DNA from you at the scene of a crime, it's just not going to match anyone else on earth unless maybe you have twin or something. You know, but this sort of matching we're talking about with the spores, it's much more iffy, and so it would be interesting to see how much weight that evidence carried in court.

CHADWICK: NPR's David Kestenbaum. Thanks David.

KESTENBAUM: You're welcome. Transcript provided by NPR, Copyright NPR.

NPR transcripts are created on a rush deadline by an NPR contractor. This text may not be in its final form and may be updated or revised in the future. Accuracy and availability may vary. The authoritative record of NPR’s programming is the audio record.

Alex Chadwick
For more than 30 years, Alex Chadwick has been bringing the world to NPR listeners as an NPR News producer, program host and currently senior correspondent. He's reported from every continent except Antarctica.
David Kestenbaum is a correspondent for NPR, covering science, energy issues and, most recently, the global economy for NPR's multimedia project Planet Money. David has been a science correspondent for NPR since 1999. He came to journalism the usual way — by getting a Ph.D. in physics first.
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