IN THIS ISSUE .
January 20, 2010
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Like a pulsing blue shower, E. coli cells flash in synchrony. Genes inserted into each cell turn a fluorescent protein on and off at regular intervals. When enough cells grow in the colony, a phenomenon called quorum sensing allows them to switch from blinking independently to blinking in unison. Researchers can watch waves of light propagate across the colony. Adjusting the temperature, chemical composition or other conditions can change the frequency and amplitude of the waves. Because the blinks react to subtle changes in the environment, synchronized oscillators like this one could one day allow biologists to build cellular sensors that detect pollutants or help deliver drugs. Courtesy of bioengineer Jeff Hasty, University of California, San Diego.
Got any rotten produce or expired canned goods lying around? Your body doesn't. Its equivalent of rancid food—faulty or unneeded proteins—are quickly marked for disposal by a chain of four or more ubiquitin molecules. But this molecular housekeeping happens so quickly that no one really understood the process until now. Caltech biochemists led by Raymond Deshaies used a method biochemically akin to stop-action photography to watch the reaction. They witnessed one ubiquitin molecule attaching to a protein, then others following within milliseconds. Because ubiquitin is found throughout nature, a deeper understanding of its action could have implications that are unforeseen and, well, ubiquitous.
Many people think of bone as an inert substance, but like other parts of our bodies its structure can change in ways that affect our health. Now, researchers led by chemist Ayyalusamy Ramamoorthy of the University of Michigan have developed a method called "magic-angle spinning" that lets them probe the structure of individual molecules that make up bone. Using the technique, they observed that collagen—one of bone's main constituents—becomes less flexible with water loss, which is a common feature of aging. The new technique may enable scientists to more closely examine how factors like age and disease influence bone health.
This work also was supported by NIH's National Institute of Diabetes and Digestive and Kidney Diseases, National Institute of Arthritis and Musculoskeletal and Skin Diseases and National Center for Research Resources.
Analyzing 300,000 genetic markers in hundreds of individuals has provided a genome-wide perspective of African-American ancestry. Led by University of Pennsylvania geneticist Sarah Tishkoff and Cornell University computational biologist Carlos Bustamante, a research team found that genomic diversity among African Americans ranges from as little as 1 percent West African ancestry to as much as 99 percent. The data also revealed large differences in the percentage of European ancestry. By showing that African-American ancestry is much more diverse than previously thought, the study supports the value of understanding the genetic bases of disease susceptibility and drug response on an individual level.
All living things carry out complex social interactions that can play a big role in their survival and, ultimately, evolution. Scientists know, for instance, that creatures with similar genes are usually more likely to cooperate than compete. To better understand these behaviors in social bacteria, Indiana University biologist Gregory Velicer studied Myxococcus Xanthus cells that normally work together to survive starvation. He found that antagonistic behaviors evolved even among cells that were extremely similar, indicating that their subtle genetic differences can drive some competitive behaviors. This finding may help us better understand how our body's bacteria compete for resources and develop antibiotic resistance.