Tuesday, September 1, 2009
Water striders, the familiar semi-aquatic bugs gliding across the lake at the cottage, have a novel body form that allows them to walk on water, but this was not always the case.
Achieving the gliding ability required the evolution of a unique arrangement of the legs, with the mid-legs greatly elongated. Scientists at the University of Toronto's Department of Ecology and Evolutionary Biology have discovered the gene behind this evolutionary change.
Called the Hox gene, Ultrabithorax is known to play a role in lengthening legs in other insects. Professor Locke Rowe and his team investigated where Ultrabithorax is expressed and how it functions in the water strider body plan using the cutting edge tools of molecular biology.
"To our surprise, we discovered that Ultrabithorax performs opposite functions in different limbs," said Rowe. "It lengthens the mid-legs but shortens the hind-legs to establish this unusual body plan that allows water striders to glide on the water surface."
Groups of organisms are characterized by a few defining characteristics. In the case of humans it is walking upright and in the case of spiders it is eight legs. It is these defining characteristics that account for much of the diversity we see in life. Determining how these major evolutionary changes happen is a central goal of evolutionary biology, explained Rowe.
"Many have marveled at the ability of water striders to walk on water, and we are excited to have discovered the gene that has affected this evolutionary change."
Other research team members include Ehab Abouheif and lead author Abderrahman Khila, both of McGill University. The work was funded by an NSERC Steacie Fellowship and by NSERC Discovery Grants and is published in PLoS Genetics.
(Photo: U. Toronto)
University of Toronto
As tags on household appliances warn, water conducts electricity extremely well. Now, scientists have found that enhanced electrical conductivity in parts of Earth's mantle may signal the presence of water far below our planet's surface.
The researchers created the first global three-dimensional map of electrical conductivity in the mantle. Results of their study are published in the journal Nature.
The areas of high conductivity coincide with subduction zones--places where tectonic plates are being subducted beneath the Earth's crust, say the Oregon State University (OSU) scientists who performed the research. They used electromagnetic induction sounding of the Earth's mantle in the study. The method is very sensitive to interconnecting pockets of fluid in rocks and minerals.
"This work is important because it complements global 3-D seismic imaging of Earth's interior, which uses sound waves generated by earthquakes," said Robin Reichlin, program director in the National Science Foundation (NSF)'s Division of Earth Sciences, which funded the research. "Scientists may be able to combine these two methods to tease out a more detailed understanding of variations in Earth's inner composition, water content and temperature."
Subducting plates are comparatively colder than surrounding mantle materials and should be less conductive, geologists have believed. However, the OSU scientists suggest, conductivity in these areas may be enhanced by water drawn downward during the subduction process.
"Many earth scientists thought that tectonic plates are not likely to carry much, if any, water deep into the Earth's mantle," said Adam Schultz, a geologist at OSU and a co-author of the Nature paper. "Our model, however, clearly shows a close association between subduction zones and high conductivity. The simplest explanation is water."
The study provides new insights into the fundamental ways in which our planet works, Schultz says. Despite advances in technology, scientists are still unsure how much water lies beneath the ocean floor--and how much of it makes its way into the mantle.
The implications are myriad. Water interacts with minerals differently at different depths, and small amounts of water may change the physical properties of rocks, alter the viscosity of materials in the mantle, assist in the formation of rising plumes of melted rock, and ultimately affect what flows out on the surface.
"In fact, we don't really know how much water there is on Earth," said Gary Egbert, an oceanographer at OSU and co-author of the paper. "There is some evidence that there is many times more water below the ocean floor than there is in all the oceans of the world combined. Our results may shed some light on this question."
There may be different explanations for how the water--if indeed the conductivity is reflecting water--got there.
"If it isn't being subducted down with the plates," Schultz said, "is it primordial, down there for four billion years? Or did it come down as the plates slowly subduct, suggesting that the planet may have been much wetter a long time ago? These are fascinating questions for which we don't yet have answers."
Anna Kelbert, a post-doctoral researcher at OSU and lead author of the paper, says that the next step is to replicate the experiment with newly available data from both ground observatories and satellites, then conduct further research to better understand the water cycle and how its interaction with deep-Earth minerals works.
Ultimately, the scientists hope to produce a model quantifying how much water may be in the mantle, locked up in its rocks.
(Photo: Anna Kelbert)
National Science Foundation
Humans might not be walking the face of the Earth were it not for the ancient fusing of two prokaryotes — tiny life forms that do not have a cellular nucleus. UCLA molecular biologist James A. Lake reported important new insights about prokaryotes and the evolution of life in the Aug. 20 advance online edition of the journal Nature.
Endosymbiosis refers to a cell living within another cell. If the cells live together long enough, they will exchange genes; they merge but often keep their own cell membranes and sometimes their own genomes.
Lake has discovered the first exclusively prokaryote endosymbiosis. All other known endosymbioses have involved a eukaryote — a cell that contains a nucleus. Eukaryotes are found in all multicellular forms of life, including humans, animals and plants.
"This relationship resulted in a totally different type of life on Earth," said Lake, a UCLA distinguished professor of molecular, cell and developmental biology and of human genetics. "We thought eukaryotes always needed to be present to do it, but we were wrong."
In the Nature paper, Lake reports that two groups of prokaryotes — actinobacteria and clostridia — came together and produced "double-membrane" prokaryotes.
"Higher life would not have happened without this event," Lake said. "These are very important organisms. At the time these two early prokaryotes were evolving, there was no oxygen in the Earth's atmosphere. Humans could not live. No oxygen-breathing organisms could live."
The oxygen on the Earth is the result of a subgroup of these double-membrane prokaryotes, Lake said. This subgroup, the cyanobacteria, used the sun's energy to produce oxygen through photosynthesis. They have been tremendously productive, pumping oxygen into the atmosphere; we could not breathe without them. In addition, the double-membrane prokaryotic fusion supplied the mitochondria that are present in every human cell, he said.
"This work is a major advance in our understanding of how a group of organisms came to be that learned to harness the sun and then effected the greatest environmental change the Earth has ever seen, in this case with beneficial results," said Carl Pilcher, director of the NASA Astrobiology Institute, headquartered at the NASA Ames Research Center in Moffett Field, Calif., which co-funded the study with the National Science Foundation.
"Along came these organisms — the double-membrane prokaryotes — that could use sunlight," Lake said. "They captured this vast energy resource. They were so successful that they have more genetic diversity in them than all other prokaryotes.
"We have a flow of genes from two different organisms, clostridia and actinobacteria, together," he said. "Because the group into which they are flowing has two membranes, we hypothesize that that was an endosymbiosis that resulted in a double membrane. It looks as if a single-membrane organism has engulfed another. The genomes are telling us that the double-membrane prokaryotes combine sets of genes from the two different organisms."
For this study, Lake has looked back more than 2.5 billion years. He conducted an analysis of the genomics of the five groups of prokaryotes.
Lake is interested in learning how every organism is related.
"We all are interested in our ancestors," he said. "A friend at UC Berkeley, Alan Wilson, was the first person to collect DNA from large numbers of people around the world. He showed that we are all related to a woman who lived in Africa 200,000 years ago. Some in the media called her Eve. He called her the Lucky Mother, the mother of us all.
"In our field, we have enormous amounts of data but cannot make sense of it all. Endosymbiosis allows us to start to understanding things; it tells us that many genes are exchanged.
"We have been overlooking how important cooperation is," Lake said. "If two prokaryotes get together, they can change the world. They restructured the atmosphere of the Earth. It's a message that evolution is giving us: Cooperation is a way to get ahead."
Actinobacteria have an unusual DNA composition, with a very high amount of "G" and "C" nucleotides — chemicals whose patterns carry the data required for constructing proteins. Nucleotides are designated by the letters G (guanine), C (cytosine), A (adenine) and T (thymine); the sequence of nucleotides serves as a chemical code.
Some actinobacteria are pathogens, including ones that cause tuberculosis and leprosy. Some clostridia can photosynthesize, which no other single-membrane prokaryote does. Photosynthesis may have been developed in clostridia.
Double-membrane prokaryotes include the pathogens that cause ulcers, as well as the organisms that led to the creation of the chloroplasts that are in all green plants and which make plant growth possible.
(Photo: Reed Hutchinson/UCLA)
Pavlidis Pavlos led a team of researchers from the Aristotle University of Thessaloniki who used electrical stimulation to test the taste threshold of the soldiers and endoscopes to measure the number and shape of a kind of taste bud called fungiform papillae. He said, "Statistically important differences between the taste thresholds of smokers and non-smokers were detected. Differences concerning the shape and the vascularisation of fungiform papillae were also observed".
By applying electrical current to the tongue, a unique metallic taste can be generated. Measuring how much current is required before a person perceives this sensation allows determination of their taste sensitivity. The 28 smokers in the study group scored worse than the 34 non-smokers. Upon close examination with a contact endoscope, the smoker's tongues had flatter fungiform papillae, with a reduced blood supply. Pavlos concludes, "Nicotine may cause functional and morphological alterations of papillae, at least in young adults".
Engineers at Ohio State University have found a way to double the production of the biofuel butanol, which might someday replace gasoline in automobiles.
The process improves on the conventional method for brewing butanol in a bacterial fermentation tank.
Normally, bacteria could only produce a certain amount of butanol -- perhaps 15 grams of the chemical for every liter of water in the tank -- before the tank would become too toxic for the bacteria to survive, explained Shang-Tian Yang, professor of chemical and biomolecular engineering at Ohio State.
Yang and his colleagues developed a mutant strain of the bacterium Clostridium beijerinckii in a bioreactor containing bundles of polyester fibers. In that environment, the mutant bacteria produced up to 30 grams of butanol per liter.
The researchers reported their results at the American Chemical Society meeting Wednesday in Washington, DC.
Right now, butanol is mainly used as a solvent, or in industrial processes that make other chemicals. But experts believe that this form of alcohol holds potential as a biofuel.
Once developed as a fuel, butanol could potentially be used in conventional automobiles in place of gasoline, while producing more energy than another alternative fuel, ethanol.
Yang said that this use of his patented fibrous-bed bioreactor would ultimately save money.
“Today, the recovery and purification of butanol account for about 40 percent of the total production cost,” explained Yang, “Because we are able to create butanol at higher concentrations, we believe we can lower those recovery and purification costs and make biofuel production more economical.”
Currently, a gallon of butanol costs approximately $3.00 -- a little more than the current price for a gallon of gasoline.
The engineers are applying for a patent on the mutant bacterium and the butanol production methodology, and will work with industry to develop the technology.
Ohio State University
Etiquetas: Materials Science
Scientists have discovered the secret to easing one of the great frustrations of the millions who use smart phones, portable media players and other devices with touch- screens: Reducing their tendency to smudge and cutting glare from sunlight. In a report at the 238th National Meeting of the American Chemical Society, they describe development of a test for performance of such smudge- and reflection-resistant coatings and its use to determine how to improve that performance.
Steven R. Carlo, Ph.D., and colleagues note in the new study that consumer electronics companies value the appearance of their flagship devices just as much as their functionality. As a result, smudge, scratch and reflective resistant coatings have become standard on high-end touch-screen cell phones and MP3 players. These coatings are effective. However, their structure and mechanisms are poorly understood, so Carlo and colleagues developed a test to determine the chemical composition and effectiveness of smudge and reflective resistant materials. The test could also lead to a better understanding of the chemistry of these coatings and allow improved formulations and performance, Carlo says.
"Surfaces are particularly important in consumer products. This work investigates how products can be modified to reduce smudging and reflections. These modifications can offer improved resistance to fingerprints, anti-reflection properties or enhanced physical resistance," Carlo explains.
The basis of anti-smudge coatings is a compound called perfluoro alkyl ether, a derivative of Teflon with added ether groups to enhance its repellent effects. Anti-reflective materials use alternating layers of material, including silica and aluminum layers, to bend and diffuse light to reduce glare.
Since traditional chemical techniques could not be used on these super-thin coatings, Carlo and his team used depth profile X-ray photoelectron spectroscopy (XPS). That's a tool for comparing the chemistry of these coatings to predict their performance. The data allowed them to compare chain length, degree of branching and the hydrocarbon and fluoroether content of various samples. The fluoroether content has a key effect in enhancing efficacy. Anti-reflective coatings need alternating layers, which have differences in their refractive index (RI), a measure of how fast light travels through a material. Fluorocarbons in general have low RI and they offer anti-smudge properties. XPS allowed the scientists to visualize the multi-layer structure and the chemical species present in each layer. In general, the greater the number of layers there are in a coating, the greater the anti-reflective properties. Carlo and his team also discovered that more silica and aluminum layers led to better glare reduction.
(Photo: The American Chemical Society)