Escherichia coli

From Wikiquote
Jump to navigation Jump to search

Escherichia coli (also known as E. coli) is a gram-negative, facultatively anaerobic, rod-shaped non-spore-forming rod, ~1-2 µm wide, 3-30 µm long bacterium of the genus Escherichia that is commonly found in the lower intestine of warm-blooded organisms (endotherms). Most E. coli strains are harmless, but some serotypes can cause serious food poisoning in their hosts, and are occasionally responsible for product recalls due to food contamination. The harmless strains are part of the normal flora of the gut, and can benefit their hosts by producing vitamin K2, and preventing colonization of the intestine with pathogenic bacteria.


  • The equivalent fundamental unit in DNA is the nucleotide base. Since there are 4 possible bases, the information content of each base is equivalent to 2 bits. The common gut bacterium Escherichia coli has a genome of 4 mega-bases or 8 megabits. The crested newt, Triturus cristatus, has 40,000 megabits. The 5,000-fold ratio between crested newt and bacterium is about the same as that between my present computer and my first one. We humans have 5,000 mega-bases or 6,000 megabits. This is 750 times as great as the bacterium (which satisfies our vanity), but what are we to make of the newt trumping us sixfold? We'd like to think that genome size is not strictly proportional to what it does: presumably quite a lot of that newt DNA isn't doing anything. This is certainly true. It is also true of most of our DNA.
  • The natural balance produced by the Rock, Paper, Scissors scenario is not confined to lizards. Researchers from Stanford and Yale have discovered that the same scenario is responsible for preserving biodiversity in bacterial neighborhoods. The bacteria concerned are Escherichia coli—the type that are found in all of our digestive systems. The researchers mixed three natural populations together in a petri dish. One population produced a natural antibiotic called “colicin” but was immune to its effects, as snakes are immune to poisoning by their own venom. A second population was sensitive to the colicin but could grow faster than the third population, which was resistant to colicin. The net result was that each established its own territory in the petri dish. The colicin producers could kill off any nearby bacteria that were sensitive to the colicin, the colicin-sensitive bacteria could use their faster growth rate to displace the colicin-resistant bacteria, and the resistant bacteria could in turn use their immunity to displace the colicin producers!
    • Len Fisher, Rock, Paper, Scissors (2008), Ch. 4 : Rock, Paper, Scissors
  • Without their threatening presence, there is no need for gene recombination or sexual (versus asexual) reproduction. We wouldn’t have to keep up with the Joneses, or in this case the Escherichia coli or the Entamoeba histolytica, which are constantly mutating to get better at attacking us so they can reproduce and survive. Disgust is the emotion that protects purity. Haidt suggests that the emotion of disgust arose when hominids became meat eaters. It appears to be a uniquely human emotion.
    • Michael S. Gazzaniga, Human: The Science Behind What Makes Us Unique (2008), Ch. 4 : The Moral Compass Within
  • Bacteria, the study of which has formed a great part of the foundation of genetics and molecular biology, are the organisms which, because of their huge numbers, produce the most mutants. This is why they gave rise to an infinite variety of species, called strains, which can be revealed by breeding or tests. Like Erophila verna, bacteria, despite their great production of intraspecific varieties, exhibit a great fidelity to their species. The bacillus Escherichia coli, whose mutants have been studied very carefully, is the best example. The reader will agree that it is surprising, to say the least, to want to prove evolution and to discover its mechanisms and then to choose as a material for this study a being which practically stabilized a billion years ago!
    • Pierre P. Grassé, Evolution of Living Organisms: Evidence for a New Theory of Transformation (1977), p. 87
  • Oscillatory reactions of the epigenetic type are also well known. They occur as a consequence of regulatory processes at the cellular level. Proteins are generally stable molecules, whereas catalysis is a very fast process. Thus, it is not unusual for the protein level in a cell to be too high, in which case other bodily substances act to suppress the synthesis of macromolecules. Such feedback gives rise to oscillations and has been studied in detail in, for example, the regulation of the lactose operon in the bacterium Escherichia coli.
    • Ilya Prigogine, From Being to Becoming (1980), Ch. 5 : Self-Organization
Wikipedia has an article about: