pathogenic microbes


Dr Warhol’s Periodic Table of Microbes

68. Er. Escherichia

Everyone who has every taken microbiology, or even general biology, knows Escherichia. For that matter, if you are aware of news reports, you’ve heard of it. And maybe, if you are an art major, you think you’ve heard of it, but Maurits Escher and Theodor Escherich were two entirely different people, one a brilliant artist and the other an amazing bacteriologist.

Escherichia is one of the most-studied organisms in the universe. A Google Scholar search can turn up nearly 3 million hits (in 0.04 seconds), and other search devices will find even more. (In comparison Kim Kardashian shows up about 3 thousand times on Google Scholar, but dominates normal Google at 150 million hits.) Unlike some of our other friends that have hundreds of species, the genus Escherichia has only 8, and the big kahuna is Escherichia coli.

The basic description of the microbe is that it is a Gram negative rod that does not form spores, it likes oxygen but can live without it, and it mostly exists happily and harmlessly in the intestines of warm-blooded animals. That said, given the chance, E. coli can be a serious pathogen. It is a common cause of urinary tract infections, and you shouldn’t be too surprised to find it anywhere opportunistic agents strike. E. coli makes headlines when it causes food poisoning with intensity that varies from watery traveler’s diarrhea to bloody invasive diarrhea that leads to kidney failure and death (let’s not forget the  cramping, fever, and vomiting that can also occur). It seems about every month or so there is a major food recall due to contamination with E. coli.

Instead of being delineated by species, E. coli is subdivided into strains based on biochemistry, antigenicity, and virulence. So we have, among others: enterotoxigenic E. coli (ETEC), enteroinvasive E. coli (EIEC), enterohemorrhagic E. coli (EHEC), enteropathogenic E. coli (EPEC), and enteroaggregative E. coli (EAggEC).

Don’t think that Escherichia is all doom and gloom. The organism is a marvelous toolbox for subcellular biochemistry and genetics. Lac operon? E. coli! Plasmids? E. coli! Hfr? E. coli! Pilli? E. coli! Chemotaxis? E. coli! Gene splicing? E. coli! Antibiotic resistance? E. coli! Motility? E. coli! cAMP? E. coli! If you want to study almost anything, you can find an application for it in E.coli.

Escherichia cells are a Gram negative rods that are usually 0.5 microns wide by 2 microns long.

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