Word: bacterias
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...medicine's worst nightmares is the development of a drug-resistant strain of severe invasive strep A, the infamous flesh-eating bacteria. What appears to make this variant of strep such a quick and vicious killer is that the bacterium itself is infected with a virus, which spurs the germ to produce especially powerful toxins. (It was severe, invasive strep A that killed Muppeteer Jim Henson in 1990.) If strep A is on the rise, as some believe, it will be dosed with antibiotics, and may well become resistant to some or all of the drugs...
...difference between animals and bacteria is that a new generation comes along every few years in large beasts -- but as often as every 20 minutes in microbes. That speeds up the evolutionary process considerably. Germs have a second advantage as well: they're a lot more promiscuous than people are. Even though bacteria can reproduce asexually by splitting in two, they often link up with other microbes of the same species or even a different species. In those cases, the bacteria often swap bits of genetic material (their DNA) before reproducing...
...picking up genes as well. The DNA can come from viruses, which have acquired it while infecting other microbes. Some types of pneumococcus, which causes a form of pneumonia, even indulge in a microbial version of necrophilia by soaking up DNA that spills out of dead or dying bacteria. This versatility means bacteria can acquire useful traits without having to wait for mutations in the immediate family...
...frequently stop taking antibiotics when their symptoms go away but before an infection is entirely cleared up. That suppresses susceptible microbes but allows partially resistant ones to flourish. People with viral infections sometimes demand antibiotics, even though the drugs are useless against viruses. This, too, weeds out whatever susceptible bacteria are lurking in their bodies and promotes the growth of their hardier brethren. In many countries, antibiotics are available over the counter, which lets patients diagnose and dose themselves, often inappropriately. And high-tech farmers have learned that mixing low doses of antibiotics into cattle feed makes the animals grow...
...Unlike bacteria and protozoans, which are full-fledged living cells, capable of taking in nourishment and reproducing on their own, viruses are only half alive at best. They consist of little more than a shell of protein and a bit of genetic material (DNA or its chemical cousin RNA), which contains instructions for making more viruses -- but no machinery to do the job. In order to reproduce, a virus has to invade a cell, co-opting the cell's own DNA to create a virus factory. The cell -- in an animal, a plant or even a bacterium -- can be physically...