Noting an interesting tidbit in John Gribbin's new book, +quot;In the Beginning+quot; (Lit

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Noting an interesting tidbit in John Gribbin's new book, "In the Beginning" (Little, Brown & Co.; 1993), which is about evolution, life, and the universe as a whole... Scanned in, page 114---> (Reference Lynn Margulis' theory that bacteria became symbiotic with eukaryptic cells) "This would all still seem a little far-fetched, though, were it not for an extraordinary discovery made by Kwang Jeon, of the University of Tennessee, who spotted this kind of evolution at work in his laboratory, and gave it a helping hand. Jeon was working with microscopic, single-celled creatures called amoebas, when they were struck by a disease that spread through all the amoeba colonies in his laboratory. Almost all of them stopped feeding, ceased dividing into two to reproduce, and eventually died. Just a few of the amoebas seemed to be struggling along in spite of the disease. dividing about once every month instead of once every day, as they had done when they were healthy. The obvious thing for Jeon to have done would have been to discard all the diseased amoebas and start again with a fresh, uninfected batch, but he was curious about the nature of the disease that had infected them. Studying the diseased amoebas through a microscope, he found that they contained tens of thousands of tiny, rod-shaped bacteria which had invaded the cells of the amoebas, disrupting their biological processes and killing them. And yet, a few of the 'bacteriarized' amoebas were struggling along, albeit with difficulty. Jeon decided to keep a colony of the survivors, and watch what happened to them. For five years Jeon tended the colony, regularly picking out the ones that fed and reproduced best and letting the others die. This is a classic example of the kind of artificial selection used by pigeon breeders or dog fanciers. But because of the rapid life cycle of the amoebas, the effects of selection became apparent much more quickly than they do when breeding mammals or birds, which take much longer to reproduce. At the end of five years, Jeon had a colony of bacteriarized amoebas that seemed healthy in all respects, and were dividing every day, just like their non-infected cousins. Each of these amoebas, though, still contained as many as 40,000 bacteria. This is still not the end of the story. Usually, with amoebas of the same species, it is possible to tweak out the nuclei from two different cells and swap them over. The amoebas with the swapped nuclei happily carry on growing and dividing, since each nucleus carries essentially the same DNA 'message', and each cell contains essentially the same chemical 'factories'. But when Jeon removed the nuclei from the new strain of bacteriarized amoebas and put them into non- bacteriarized amoebas from the original species whose nuclei had been removed, the cells without the bacteria died. And yet if, just before it died, the 'clean' cell containing the new nucleus was deliberately infected with a few of the bacteria, they reproduced and increased up to a population of about 40,000, while the cell recovered its health. The nuclei from the bacteriarized cells could no longer function properly without the bacteria. Partly as a result of an accidental infection, and partly thanks to Jeon's artificial selection, a new symbiotic species of amoeba had been created. This particular new species would probably not have survived without his aid. Even the few original infected cells that did reproduce were very sensitive to heat and cold, and much more easily killed by antibiotics than normal, 'non-bacteriarized' amoebas. But imagine the situation, something over 1.5 billion years ago, when different kinds of cell existed side by side in the waters of the Earth. Large cells, containing a relative wealth of biological material, would have been the prey of smaller bacteria, which would invade them (like the bacteria that invaded Jeon's amoebas) and feast upon thc resources they containcd. But when the host died, many of the invaders would die as well."


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