Word: bacterias
(lookup in dictionary)
(lookup stats)
Dates: all
Sort By: most recent first
(reverse)
...TIME, March 12)-that existed about 2 billion years ago. With the older specimens, he now believes "we are getting close to an area in time-say within a half-billion years-of possible transition between non-biologically produced material and the first presumptive primeval organism." Discovery of the bacteria-like organisms, says Barghoorn, indicates that there was water and erosion 3 billion years ago and that biological processes then were comparable to those today...
...paper presented Thursday at a Geological Society of America meeting in Kansas City, Mo., Barghoorn detailed the discovery of tiny organic fossils in pre-Cambrian rock. A radio isotope test proved that the rod-like bacteria were at least three billion years...
With Stand-ins. To check and expand on these hypotheses, Lwoff chose to work with single-celled organisms, such as bacteria, because they have a single chromosome (whereas man has 46). As stand-ins for genes he chose viruses that infect bacteria (bacterio-phages), because their cores consist of nucleic acid. What actually happens Lwoff found, is not as simple as had been thought. The viral nucleic acid, in effect masquerading as a gene, might do one of two things after invading a bacterium: 1) stimulate the bacterial cell to produce hundreds of copies of the virus particle, and destroy...
Reaching Forward. So far, these hypotheses have been substantially proved for bacteria, and there is convincing evidence of the existence of "messenger RNA" in mammalian cells. As a result, there is a great temptation to extrapolate all the way from microbe to man and assume that long-dormant viruses may belatedly trigger cancerous changes in human cells. The evidence for this, so far, is extremely tenuous. But the Nobel Prize committee, which has sometimes been as much as 30 years late in recognizing achievement, has now reached toward the future in making its 1965 award...
Breakout After Stress. Like viruses, PPLO can invade living cells and destroy them from within. Like bacteria, they can grow in a chemical broth independently of living cells. Though PPLO differ from bacteria in having ill-defined shapes (see diagram), some are believed to be variant forms of bacteria. And like many bacteria, some PPLO are natural inhabitants of the human respiratory, intestinal and genital tracts, where they cause no disease until they are activated when the individual has been subjected to unusual stress...