Campylobacter "twisted bacterium" sp. I need quotes around my middle name. Note the stringy flagella. U.S. Agricultural Research Service
Not long after I became a health and environment reporter in Wyoming, I was assigned to cover a smokeless tobacco talk given by a scientist from the Mayo Clinic.
Smokeless tobacco (aka moist tobacco, chewing tobacco, and spit tobacco), he said among other points, supported huge populations of live bacteria.
That was surprising to me. I’d never thought about it before, but it did make sense. The tobacco companies don’t exactly autoclave their product.
Since it was my job to report on the talk, I reported that the substance was “teeming with bacteria”, a statement I felt was amply supported by the evidence presented by this guy.
The next day I got a call from a scientist at a state university in the south. He said he was calling to correct what he claimed were the inaccuracies in my story. He then proceeded to enumerate my alleged errors. I clearly remember him singling out the “teeming bacteria” statement.
“Come on,” he said.
For those of you not in the United States, the Mayo Clinic is one of the top, if not the top, medical centers in the country. And though the Mayo Clinic scientist backed up my reporting on his talk when I subsequently called (and the story was just about his talk — not an attempt at a broader survey of the science, even if the southern scientist’s points had been backed up by a broader literature), I felt stung, to be sure. The Gulf Coast scientist even went so far as to send me some of his papers supposedly disproving what I’d written. It was all rather odd. I ask you, why would a scientist at a university 1,000 miles away go out of his way to call a reporter at a circulation 18,000 paper in Wyoming to correct alleged errors that in no way mentioned his research? How would he even know about the story?
Well, guess what? It turns out that not only is smokeless tobacco teeming with live bacteria, so are dry cigarettes, according to a recent article in Science News (see also here for an earlier article). Scientists have found genetic markers for hundreds of species in cigarettes, and have cultured several of them out of packages purchased off the shelf.
When cultured with blood, some of these bacteria can digest it. And as the article points out, scientists have long known smokers have higher rates of lung infection. Doctors always assumed that was due to immune system suppression. But inoculating your lungs with bacteria or their spores several times a day probably doesn’t help.
In retrospect, it’s not surprising. You take leaves. You hang them up in a moist, dark, warm place (a tobacco barn). You wait. In plant pathology, we called this a moist chamber*. It’s how we coaxed fungi to fruit so we could grab their spores for pure culture. Bacteria seem to like the treatment too: scientists found Campylobacter, Clostridium, Corynebacterium, Klebsiella, Staphylococcus, Pseudomonas aeruginosa, Stenotrophomonas maltophilia, Escherischia coli, and Bacillus subtilis signatures in cigarette tobacco, according to the Science News article. Not only is this a who’s who of the pathogenic human bacteria world (although is should be noted many species in these genera are not pathogens under ordinary circumstances), these and other bacteria are responsible for producing the most potent carcinogens in cigarette smoke — nitrosamines — when they start chowing down on tobacco leaves. Nor is this the first time cigarettes were found to be hosting . . . er . . . organisms. Cigarettes are often contaminated with plant viruses too. Though entirely harmless to humans, it’s been known for years that people who’ve handled cigarette tobacco can transmit tobacco mosaic virus.
Now don’t get me wrong — the presence of some bacteria is no reason not to eat or drink a food. Trust me, practically everything you put in your mouth has bacteria in it or on it. Even freshly cooked food probably has a few bacteria or fungal spores settle on it between the pot and your plate. And we purposely introduce billions of “good” bacteria and fungi into food all the time. If you’ve been reading this blog long enough, you know I’d be just as likely to say yogurt, your kitchen sponge, and your mouth are teeming with bacteria (which they are). This story does make me wonder, however, if tea leaves experience something similar to tobacco leaves during processing. Does anyone know? But you don’t smoke tea, and the products of bacterial action on yogurt and tea leaves don’t give people cancer. Tobacco bacteria do.
Next time: a closer look at Klebsiella.
________________________________________________________
*Now that I think about it, I think we used grow lights over most of our moist chambers. But I don’t think dark would necessarily discourage fungi.
{ 1 trackback }
{ 5 comments… read them below or add one }
Wow, that’s cool stuff. Did you ever find out how the Gulf-State Researcher found your article? (I’ve often wondered at this sort of thing. The Northfield News here in Minnesota had an op-ed, followed by an exchange in Letters to the Editor, about global warming. People from overseas were writing to attempt to shoot down the science behind global warming. One wonders how they found the NN and why they cared.)
I’m curious about tea, now, too. It’s dried out in the sun, as I’m sure you know. My guess is that that’s less conducive to bacteria. Plus I seem to recall some properties of tea that inhibit bacteria growth, but that might be wishful thinking on my part.
How do the bacteria/spores survive the lit cigarette? I’m not an expert on smoking, but I’d think that that would be a pretty good sanitizer. (So, I should think, is making tea with boiling water. Not perfect, but it probably helps!)
Well, the bacteria don’t have to survive the flame. According to the Science News article, some get trapped in the filter, probably during manufacturing. Also, when you take a drag, you’re sucking in particles from all the unburned tobacco too, which is closer to you than the burning tobacco. One of the articles speculates the bacteria could hitch rides on the smoke particles as they pass by. But bacteria can travel through air all on their own, too.
I did a little checking on the tea — and one place suggested tea leaves are dried out of the sun? But they’re also much smaller than tobacco leaves, and may be dried in a much different fashion.
Hm, it does look like modern techniques use dryers, not Mr. Sun. But poking around, it looks like they dry them at 250 F for ~20 minutes. How far does that go toward killing any bacteria?
I don’t think any bacteria could proliferate or survive in that treatment. High, fast heat — that’s how we dried mushrooms to preserved them for the herbarium. In tobacco barns, on the other hand, the leaves (which are much bigger than tea leaves and not broken into pieces) take weeks to dry. If you’ve ever driven through certain parts of the south, you’ve seen them hanging from the rafters inside in long brown rows. I seem to recall you can even smell the tobacco if you crank down your car window.
Really interesting post that makes perfect sense. I’m also curious about tea leaves.