So who are the bacteria in cigarettes discussed in the last post? I don’t have time to profile them all, so we’ll briefly look at one I picked more or less because I didn’t know anything about it: Klebsiella.
- Pink colonies of Klebsiella pneumoniae in culture. Brought to you by Pepto Bismol.
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.
{ 2 comments… read them below or add one }
I wonder how one would meaningfully define the “entire life” of a microbe.
I’m not criticizing. I consider it a wondrous quality of English, and probably any natural language, that we can make statements that (as far as I can discern) utterly collapse under analysis, yet everyone takes your meaning perfectly anyhow.
I guess I’ve always thought that an individual bacteria can have a life, meaning it is “born” as the product of cell division and eventually perishes due to unfavorable environmental conditions or consumption by another organism (or maybe even just being worn out or parasitized if it hasn’t had bacterial sex lately?). But perhaps you’re right — since an individual bacterium and its progeny can divide many times before they are starved or eaten, maybe that’s an immortality of sorts. Did the life of the first bacterium that divided end when it divided? Or did it carry on as two lives? Certainly, bacterial lives are not like the lives of vertebrates, and English is a peculiar language. : ) I hope you can forgive/enjoy my liberties with it.