Klebsiella sp. are flagellum-less, rod-shaped, Gram-negative bacteria. The Gram state of a bacterium has to do with the  properties of its outer coating; Gram-positive bacteria have a membrane surmounted by a thick outer wall made of peptidoglycan that readily takes up purple Gram stain, while Gram-negative bacteria have a thin peptidoglycan cell wall sandwiched between inner and outer membranes. Knowing the Gram-state of bacteria helps microbiologists sort out what kind of bacteria they might be dealing with. That’s helpful, as you can imagine, when many of your subjects are simple balls (cocci) or rods (bacilli) that look more or less the same.

The funny name comes from a 19th century German microbiologist named Edwin Klebs. The group is in the enteric bacteria, which itself is within the Gamma-purple bacteria. Misleadingly, many purple bacteria are not purple. But they are bacteria. Tricky, I know. That’s probably why the group seems to have acquired a new name: Proteobacteria. See if you can find it on the bacterial family shrub.

As implied by the term enteric bacteria, many are found in the gut of animals, but many others roam wild and free. Like Klebsiella, they’re all Gram-negative rods, but some do have flagella. Enterobacteria contain some famous names indeed: Escherichia, Shigella(a maker of dysentery), Salmonella, Proteus, Klebsiella, Enterobacter, Erwinia(a plant pathogen that causes fire blight in apples and pears and soft rots in vegetable crispers around the world), and Yersinia, one species of which (Y. pestis) made it big as bubonic plague (aka The Black Death). There are others, too. Though Klebsiellas are sometimes human pathogens, some strains live happily in your gut or on your skin, and many others thrive in the environment and may never see a human their entire lives.

There are presently about seven species of Klebsiella known, and they are becoming important as hospital-acquired (nosocomial) infections. Now we don’t know what species was in the tobacco the researchers studied — they only narrowed it to genus with their genetic screens. Perhaps many species in this genus were present. But take note of the final sentence from this WebMD article about Klebsiella pneumoniae:

Infection with Klebsiella organisms occurs in the lungs, where they cause destructive changes. Necrosis, inflammation, and hemorrhage occur within lung tissue, sometimes producing a thick, bloody, mucoid sputum described as currant jelly sputum. The illness typically affects middle-aged and older men with debilitating diseases such as alcoholism, diabetes, or chronic bronchopulmonary disease. This patient population is believed to have impaired respiratory host defenses. The organisms gain access after the host aspirates colonizing oropharyngeal microbes into the lower respiratory tract.

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.

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*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.