BTW, the world is worth 33 trillion dollars according to the authors, but I suspect that may be an undervaluation.
By the way, many cosmologists are excited about another related finding. The earth is constantly being bombarded by small comets up to the size of a house; in effect, large cosmic snowballs. These appear to impact the earth at a rate of 5-30 a minute, or up to 43,000 a day! Because they are mostly water, and given the frequency of impact, they could add as much as an inch of water to the earth every 10,000 years or so. Or, over all of earth's history, they could be responsible for most of the liquid water on earth's surface. Because these small comets break up very high above the atmosphere (600-15,000 miles), the organic constituents they contain may not burn up upon reentry. In other words, this constant rain of small comets could have had enormous impact (no pun intended) on the origin and evolution of the biosphere. The story was covered in the May 29 issue of the NY Times, and was even the subject of a Times editorial on May 30. These new data are sparking intense debate among cosmologists and biologists interested in the origin of life. Stay tuned for more updates on comets and life.......
Mass spawning by coral animals has been known for about 10 years (a fantastic view of that spawning can be seen in a Nova video on the Great Barrier Reef). The present paper shows that a similar phenomenon, although with some interesting differences, also occurs in green siphonaceous algae that inhabit reefs. The paper closes with a call for more research to investigate mass spawning of algae on reefs, which will give us better knowledge and appreciation of reef biology in general and perhaps information and attention that can help save these fragile, ecosystems rich in biodiversity.
Wilmut, I., A.E. Schroeder, J. McWhir, A.J. Kind and K.H.S. Campbell. Viable offspring derived from fetal and adult mammalian cells. Nature 385:810-813, 1997.
The same issue of Nature also has three interesting commentary pieces on the subject (pp. 753, 757, 769).
The March 10 issue of Time has a special section devoted to the issue, and the March 3 NY Times also had a special section, which is now available on the Times web site (http://www.nytimes.com).
It's quite interesting that the original Nature article does not directly address the cloning issue per se (that is, cloning as a major breakthrough). Instead, the purpose of the paper was to investigate the potential factors that prevent the use of nuclei of differentiated cells for full term cloning, and how to get around the problem by manipulating the cell cycle (forcing the cells into G0 before using the nuclei for implantation into enucleated eggs). The press instead focused on the cloning per se and its implications for humans. It is also interesting that press reports were somewhat misleading in saying that the nuclei came from mammary cells. Actually, while the original source was mammary tissue, the cells were first cultured and then forced into G0 before use. Cells from other sources were successfully employed as well.
The earliest fossils, apparently of cyanobacteria, have been dated to around 3.5 billion years ago in ancient stromatolites. It is thought that from its formation around 4.6 billion years ago until about 3.8 billion years ago, the earth was chaotic in that it was probably bombarded by comets and asteroids left over from the formation of the solar system. Some of these objects would have been large enough to vaporize much of the primitive oceans. Thus, the question of just when life arose is of interest for a number of reasons. This paper uses the ion microprobe and mass spectrometry to measure the ratio of carbon 13 to carbon 12 in organic carbon grains trapped in crystals of apatite found in the oldest rock formations on earth, located in southwestern Greenland and reliably dated to 3.85 billion years ago. These rocks are metamorphosed sedimentary rock deposited in early oceans. Because of the high heat and pressure of the metamorphic process, no actual fossils have survived. However, traces of once living material might be found in another form, in the carbon grains trapped in the apatite crystals. Apatite, a mineral of calcium and phospate, is often formed by biological processes. Carbon deposited by inorganic means shows no significant enrichment in either of the two carbon isotopes, but because organisms preferentially utilize carbon 12, the ratio of carbon 13 to carbon 12 is much smaller in organically accumulated carbon. The results described in this paper show that the carbon grains in the ancient Greenland rocks are enriched in carbon 12 to a degree that cannot be accounted for except by living processes, based on current knowledge. In other words, the origin of life has been pushed back to at least 3.85 billion years ago. This is significant in that it places the origin around the time when the earth was still being bombarded with large extraterrestrial bodies. Thus, the results may also support the emerging hypothesis that life arose (and/or survived the impacts) at the bottom of the oceans.
The same issue of Nature has a News and Views summary of this article, on p. 21. The story was also covered in Science News, November 9, 1996, p. 292, as well as in the New York Times, November 7, 1996. All these articles are available in the Hot Papers file in the BLC.
Cellulose is the most abundant macromolecule on earth. It has been estimated that about 100 billion tons of it are made annually by plants alone. Bacteria, slime molds and other organisms also make cellulose. Because cellulose is the major structural component of plant cells walls, it makes a significant contribution to the mechanical properties of the wall and thereby helps determine the shape and growth characteristics of plant cells. In addition, because cellulose makes the wall rigid, it largely accounts for the supporting role of the wall in plants and thus the evolutionary success of plants as large, sessile, terrestrial, photoautotrophic organisms. That tree out there is standing in large measure because of cellulose in its walls. Cellulose is also of major agronomic importance, as the wood used in our houses, the paper on which we write, and the cotton fibers we wear in our clothing.
Cellulose is a beta 1,4 glucan, composed of chains of thousands of repeating glucose units. The chains are associated in higher order crystalline fibrils.
Because of its significance, biochemists have long dreamed of isolating and characterizing the synthase, or enzymatic machinery, that polymerizes cellulose in plants. However, plants have consistently outsmarted them! As plants were ground up for study, cell fractions switched from making cellulose to another polysaccharide, called callose, a beta 1,3 glucan. Plants deposit callose during injury responses; it helps seal various pores between cells. In other words, plants were only doing what comes naturally when biochemists ground them up. Unfortunately, that left us without an assay for cellulose synthase, and thus a firmly locked wooden door barred our way for a long time.
Enter molecular biology. Why not do an end run and clone the gene for cellulose synthase first, then use the gene to get the protein?! The first breakthrough came a few years ago when genes for bacterial cellulose synthase were cloned. Based on other studies indicating that the plant genes probably contain at least short sequences of homology at the active sites, a combined group of scientists from Israel and the biotech company Calgene just identified two genes in cotton fibers that are prime candidates for cellulose synthase. Cotton is a logical source because the fiber walls consist of 100% cellulose, and the timing of rapid cellulose deposition is well known (about 21 days after flowering). In other words, they knew when to look for high expression of cellulose synthase genes, and therefore high levels of mRNA. By the way, cotton fibers are thread-like extensions of epidermal cells on the surface of developing seeds. The cotton boll is the fruit containing the seeds. The above paper describes this work.
This article discusses fascinating discoveries made about life associated with deep-sea thermal vents. It also provides great insight into just how curiosity, determination, and hunches often pay off in important discoveries. The article ends with a stimulating proposal that photosynthesis originated as a thermal sensory system allowing organisms to survive around deep sea thermal vents, rather than as a mechanism to capture the energy of sunlight. The latter may have come later as thermal vent organisms were transported to shallow waters.
This article presents exciting new data on the relationship between a new variant of human Creutzfeld-Jakob Disease (CJD) and Bovine Spongiform Encephalopathy (BSE; mad cow disease) that have caused widespread concern and wholesale slaughter of cattle in England. The outbreak has had major political, social and economic repercussions in Europe and still dominates the headlines. CJD is a fatal, neuropathological disease in humans. BSE kills cattle. The diseases are caused by prions, which are believed to be infectious proteins devoid of nucleic acid. Recently, a new variant of CJD was discovered in England, and has been traced to people who consumed infected cattle. The disease differs from other CJD in its early onset. However, the proposal that infected people had caught BSE has been very controversial. In this paper, the authors present biochemical data to support the hypothesis. It also provides insight into how an infectious protein might work. The accompanying News and Views article provides a more general explanation directed toward the non-specialist, so you might want to read it first.