Bacteria hardly any of us know

 kw: book reviews, nonfiction, science, bacteriology, surveys

Behold the largest species (so far known) of bacteria. Thiomargarita namibiensis, the "sulfur pearl from Namibia", at 300 or more microns in diameter, can be larger than the smallest parasitic wasp, shown for comparison. It is visible without a microscope, being the size of the dot of a printed "i".

This is the first species of microbe described in The Curious World of Bacteria, by Ludger Wess (originally in German, translated by Jamie McIntosh). The author made many difficult choices to select just 50 species of Bacteria and Archaea for this book. Although Bacteria and Archaea are different domains of life, most of us, specialists included, usually use the term "bacteria" to speak of them all.

If they think of them at all, most people consider bacteria to be primitive life forms. Few realize that they have been subject to the same 4+ billion years of evolutionary history as every other kind of life on Earth. Most are less than 10 microns (or 0.01 mm) in their longest dimension. A few are smaller than 1 micron. But they come in a wide array of sizes and shapes.

Even more various are their metabolisms. Many species don't need oxygen—some are killed by it—and "breathe" sulfur or hydrogen plus carbonate, or even iron oxide. The author points out that life is energized by the transfer of electrons, by oxidation and reduction reactions. I learned a mnemonic in chemistry class: LEO & GER. LEO = "Loss of Electrons is Oxidation". Leo is the Lion, who says "Grr" (GER), which = "Gain of Electrons is Reduction".

When we use oxygen to oxidize chemicals in our bodies to get energy, the oxygen is reduced: Electrons move from some molecule to the oxygen. This rod-shaped bacterium, Desulforidis audaxviator, reduces sulfur instead of oxygen. The rod-shaped cells are about 5 microns long, but very narrow, 1/3 of a micron. This critter is found in deep mines, where some populations have been out of contact with Earth's surface for 25 million years.

Many folks only know about "bad" bacteria. By the way, the Archaea are not pathogenic. None of them. So all disease-causing "germs" are Bacteria. 

Certainly some great plagues have arisen from specific Bacteria. "The Plague", or the Black Plague, is possibly the most famous. The cause is Yersinia pestis, where "pest" means Plague in European languages. Like many bacterial diseases, these need a vector, or in this case, two vectors: The rat flea and the black rat.

The Plague changed the course of European history, twice, once in the late Roman Empire ("Justinian Plague") and once again some 700 years later. It still crops up here and there, and is a lot more deadly than COVID-19, but because of indirect spread (fleas+rats), it doesn't pose as much of a threat.

This is a book to read right through, as I tend to do, or to browse here and there for interesting articles. Either way, it's very well written and very informative. The author is young enough to write a few more books; maybe he'll pick another 50 (he has thousands of interesting species to choose among!) and write a sequel. Luscious thought!