1- OrIgInal ArtIcle: GIbson, D.G. et al., Science Express (2010).
A team of genome researchers at the J. Craig Venter Institute in the U.S recently announced that after almost 15 years of work and with a budget of $40 million, they had finally built the first bacterial strain with a completely synthetic genome. In the study, researchers chopped the genome of Mycoplasma mycodies into 1,000 pieces in the computer, chemically synthesized these fragments and assembled them into an artificial chromosome in yeast cells. The reconstructed artificial genome was subsequently transferred to a closely related bacterium Mycoplasma capricolum, whose genome was removed. Remarkably, the strain with the artificial genome was able to guide the protein machinery of the host cells, produce the necessary enzymes and macromolecules for a bacterium to survive and most importantly to grow and divide. Team leader Prof. J. Craig Venter, best known for his pioneering efforts in human genome mapping project, commented on their findings as “we created a ‘synthetic cell’ and it is the first self-replicating species we’ve had on the planet whose parent is computer.” Many media sources also publicized the study as the first successful creation of the artificial life. As much as the scientific community agreed that the synthesis, transfer and retention of a functional synthetic genome is a breakthrough, most of the scientists have found Prof. Venter’s comments and the media’s reflection on the study to be somewhat of an overstatement. It would be quite unfair to call the new bacteria an example of “artificial life.” The synthesized genome was a copy of another living bacterium with slight modifications. The genome is a blueprint, whereas the proteins perform the actual cellular functions. This new approach shows that we can copy the book of cellular blueprints reliably but it brings no new parts to our inventory. Moreover, the synthetic genome had to be assembled in live yeast cells, processed with biochemical extracts from mycoplasma cells and finally transplanted into another (closely related) live cell. In other words, “natural life” was absolute prerequisite for the so-called “artificial life.” The generation of a fully functioning organism directed by machine-synthesized genome certainly represents a major step in our ability to manipulate large chunks of genetic material. It is clear that this study will positively influence many scientists, especially synthetic biologists, to try writing novel “synthetic” software to recruit the variety of organisms’ cellular hardware for solving various global problems like energy shortage or environmental pollution. However, the philosophical questions that probe the essence of life, like: “Can we reduce life to material? Is the human being ever going to be able to build a live cell from only a few chemicals?” will likely remain as major controversial issues for many years in the age of molecular biology.
Sharing the powers of Spiderman
2- Original Article: Vogel, M.J. & Steen, P.H., PNAS (published online before print on February 4, 2010).
The adhesive powers of Spiderman, jumping from one building to another and walking on the walls, attracted most of our interests. The recent invention of scientists from Cornell University brings this power from science fiction cartoons/movies to the real life. Inspired from a little creature, leaf beetle, which can stick to leaves by generating a force exceeding 100 times its body weight, these researchers designed a device which can stick to surfaces by using the adhesive powers of water. The device consists of a plate not thicker than a credit card with hundreds of tiny holes on it. The water is pumped through these holes, which builds liquid bridges between surfaces and thus generates a strong adhesive force. Simply pushing back the water un-sticks the device in a controllable and switchable manner. There are no solid moving parts nor any kinds of glue used in the system, and this makes device even more promising. The capabilities of the device are not at the level of the leaf beetle yet, but the inventors believe that it can be improved by building on the same principles. The system can potentially be used in many practical applications, such as robotics, and it can also be implemented into shoes and gloves allowing them to stick to surfaces. Accordingly, it is no longer improbable to imagine sharing the sticky-powers of Spiderman and walking on the walls very soon.
Igniting a Supernova
3-Original Article: Gilfanov, M. & Bogdan, A., Nature 463, 924 (2010).
upernova: the Rosetta stone that may help us put together the missing pieces of the cosmic jigsaw puzzle; one of the most energetic and most luminous explosions in the universe, putting out energies equivalent to what our sun could produce in 10 billion years. Yet the mechanism that produces these explosions still eludes us. Once our sun consumes its remaining fuel in another 5 billion years, it will shrink into a “white dwarf.” These compact stars are believed to produce subsequent explosions leading to supernovas if they reach beyond a critical limit of mass. One way to gain mass is to steal material from a companion star through an “accretion” process. Accretion was thought to be the most common means that might help push the mass of a white dwarf beyond the critical mass limit, until a recent study revealed that two clashing (in-spiraling) white dwarfs might be the missing fuse that ignites supernovas. German astronomers measured the X-ray flux of four nearby elliptical galaxies and the core of the Andromeda Galaxy to see whether the amount of X-rays from these galaxies are consistent with predictions based upon the accretion mechanism. Contrary to expectations, the observed X-rays were 2–3% of the amount that would have been produced if accreting white dwarfs were the primary trigger of supernova explosions. Hence, perhaps merging white dwarfs are more commonplace in the cosmos after all.
Strategy of bats finding their way
4- Original Article: Yovel Y et al., Science 327, 701 (2010).
Bats, dolphins, shrews and swiftlets use sound waves for navigation and hunting. They emit short sonar pulses and listen to the echoes reflecting back from solid objects. Microsecond differences in the arrival times of echoes are coded by detector neurons and used as a main cue for positioning objects in an environment. This phenomenon is known as biosonar. A recent study published in Science reveals one unknown part of this perfect sound processing strategy. The study shows that bats do not center the sonar beam on the target. Instead, they aim to match the maximum slope of the beam to the target in order to increase the signal-to- noise ratio. Around the sharp edge, small variations of the target position can be detected as a clear signal change in reflected sound intensity. Furthermore, the researchers showed that if the environment is very noisy, bats could bias this critical point to increase amplitude of the echoes. This powerful technique has already been employed by humans in engineering and used in various technological tools such as atomic force microcopy. Whether this strategy is used in general by other echolocating animals remains to be answered.