Word: bacterium
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Actually, one common form of "viral" pneumonia is caused by an organism that is neither a bacterium nor a virus. Known as Mycoplasma pneumoniae, or the "Eaton agent" (named for its discoverer), it is the smallest free-living agent capable of infecting man. The microbe is best known for downing whole barracks or dormitories of victims at a time. One of the few advantages of having Mycoplasma pneumonia is that, like the bacterial forms, it is susceptible to attack by antibiotics...
...seem, however, the little creatures have a rudimentary form of memory, according to two researchers at the Berkeley campus of the University of California. After performing an intriguing series of experiments, the scientists reported to the annual meeting of the American Chemical Society that the common intestinal bacterium Salmonella typhimurium can recall things in its past...
Biochemists Robert M. Macnab and Daniel Koshland were investigating a characteristic that S. typhimurium shares with many other bacteria: it responds strongly to changes in external stimuli. If, for instance, a hostile substance is introduced into its surroundings, the bacterium uses its flagella -long, hairlike appendages-to swim away from it. But if something attractive is placed near by-say, the sugar, glucose-it will move toward it. How the bacterium chooses its direction is still not fully understood, but it apparently makes its way on a trial-and-error basis. Tumbling to and fro, it senses that taking certain...
...experiment indicated that it was DNA, and not protein, that carried the genetic message. So unexpected was that finding that even Avery was at first unwilling to accept it. Eight years later, Alfred Hershey and his assistant Martha Chase demonstrated that a virus' DNA could, by taking over a bacterium, also nullify the cell's genetic instructions and replace them with its own. Only then was DNA finally accepted as the magic substance of the genes...
...complex as the system it directs. Even after two decades of intensive study only about one-third of the genes have been mapped along the length of DNA in the chromosome of so elementary a creature as the digestive-tract bacterium Escherichia coli. The reason: just a teaspoon of E. coli DNA has information capacity approximately equal to that of a computer with a storage capacity of about...