July 5, 2007, 9:27 PM CT

Amoebae control cheating by keeping it in the family

No one likes a cheater, even a single-celled one.

New research from Rice University shows how cooperative single-celled amoebae rely on family ties to keep cheaters from undermining the health of their colonies. The research appeared in the Proceedings of the National Academy of Sciences in May.

"It's very unusual to get a complete story in biology -- one that marries careful field work with painstaking work in the laboratory -- and that's what we have here," said research co-author Joan Strassmann, chair of Rice's Department of Ecology and Evolutionary Biology.

Rice's research involved the common soil microbe Dictyostelium discoideum. These amoebae can be loners in times of plenty, but when food is scarce they work together, forming colonies to ensure their survival. About one fifth of the individuals in a colony form a tall, thin stalk. The rest climb the stalk and clump together into a bulbous fruiting body that can be carried away to better environs by the wind or on the legs of passing insects.

This simple social system poses an evolutionary conundrum for biologists; the members of the stalk give themselves up altruistically to support the colony, so what's to keep more selfish strains of D. discoideum from cheating the system, avoiding the stalk and out-reproducing their altruistic neighbors"......... Posted by: Janet      Read more         Source

July 5, 2007, 9:00 PM CT

Molecular Mechanics of Phototropism

In a paper reported in the Journal of Biological Chemistry, researchers at the University of Missouri-Columbia reported molecular-level discoveries about the mechanisms of phototropism, the directional growth of plants toward or away from light.

Phototropism is initiated when photoreceptors in a plant sense directional blue light. Understanding phototropism is important because it could lead to crop improvement, said Mannie Liscum, professor in the Division of Biological Sciences in MU's College of Arts and Science and Christopher S. Bond Life Sciences Center.

"By understanding how phototropism works at a molecular level, we can work toward engineering plants that produce more biomass or have increased drought tolerance, among other things. For example, we could use this information to optimize plants' ability to capture light for photosynthesis, which would result in more energy capture and thus growth, or potentially agronomically useful biomass," Liscum said.

Liscum and doctoral student Ullas Pedmale studied the regulation of phototropic signaling in Arabidopsis thaliana, a weedy flowering plant usually used as a model in laboratory studies. Focusing on non-phototropic hypocotyls 3 (NPH3), a protein known to be essential for phototropic responses, they examined its phosphorylation, the addition or removal of a phosphate group to the protein molecule. Using a series of pharmacological therapys and immunoblot assays, the team discovered that NPH3 was a phosphorylated protein - a protein with a phosphate group attached - in seedlings grown in the darkness. When the seedlings were exposed to light, they became dephosphorylated, or lost their phosphate group......... Posted by: Erica      Read more         Source

Tue, 03 Jul 2007 05:11:40 GMT

Thymine Dimers

Summer is here, and we’re all heading outdoors to enjoy the sun. But remember to take your sunscreen, since too much sunlight can damage your cells. Small doses of sunlight are needed to create vitamin D, but larger doses attack your DNA. Ultraviolet light is the major culprit. The most energetic and dangerous wavelengths of UV light, termed UVC, are screened out (at least for now) by the ozone in the upper atmosphere. However, the weaker UV light, termed UVA and UVB, passes through the atmosphere and is powerful enough to cause chemical changes in the DNA.

Ultraviolet light is absorbed by a double bond in thymine and cytosine bases in DNA. This added energy opens up the bond and allows it to react with a neighboring base. If the neighbor is another thymine or cytosine base, it can form a covalent bond between the two bases. The most common reaction is shown here: two thymine bases have formed a tight thymine dimer, with two bonds gluing the bases together. This is not a rare event: every second you are in the sun, 50 to 100 of these dimers are formed in each skin cell!

More from David Goodsell on this molecule here. Posted by: PhilipJ      Read more     Source

Tue, 03 Jul 2007 05:06:21 GMT

Evolution

This week's is devoted to the topic of Evolution. There's so much good stuff, I don't know where to start.

Carol Kaesuk Yoon has a fantastic article about Evo-Devo. Turns out the same DNA sequences are tweaked over and over to different body plans and complex forms.

Nick Wade writes about human evolution. Think humans have stopped evolving? Think again. Human evolution continues to surprise and startle evolutionary biologists.

Carl Zimmer from the Loom covers Rich Lenski's Long Term Evolution Experiment. It's up to 40,000 generations now! Lenski is my scientific "grandfather"; my former advisor, Paul Turner, did his Ph.D. under Lenski.

John Nobel Wilford writes about the Human Family Tree. In case you haven't heard by now, "missing links" keep popping up all over the place.

Dennis Overbye ponders DNA encoded messages, a topic I covered earlier in this blog.

Natalie Angier writes about Toxoplasma gondii, every one's favorite mind parasite.

Cornelia Dean reveals that humans are not in a class by themselves.

Finally, now's your chance to pose questions to Sean B. Carroll, evolutionist extraordinaire and author of Endless Forms Most Beautiful.

Stop by Bugmenot and get a username and password, if you don't feel like registering.

Photo: Charles Darwin on the porch of Down House, Kent. Posted by: Dennehy      Read more     Source

July 2, 2007, 9:58 PM CT

Endangered Grey-Shanked Doucs in Vietnam

A team of researchers from WWF and Conservation International (CI) has discovered the world's largest known population of grey-shanked doucs (Pygathrix cinerea), increasing chances that the Endangered monkey can be saved from extinction.

The grey-shanked douc is one of the world's 25 most endangered primates and has only been recorded in the five central Vietnamese provinces of Quang Nam, Kon Tum, Quang Ngai, Binh Dinh, and Gia Lai. Fewer than 1,000 individuals are believed to still exist, and until now, only one other population with more than 100 animals was known.

"This is an exciting and important discovery because of the large size of the population," said Barney Long, Central Truong Son Conservation Landscape Coordinator for WWF Greater Mekong - Vietnam Program. "It's very rare to discover a population of this size with such high numbers in a small area, particularly for a species on the brink of extinction. This indicates that the population has not been impacted by hunting like all other known populations of the species".

Recent surveys in Que Phuoc Commune in Quang Nam Province recorded at least 116 animals (the number of individuals observed), with an estimated population of over 180 individuals. To date, only a small part of the area has been surveyed, meaning significantly more doucs may live in the adjacent forest......... Posted by: Kelly      Read more         Source

June 27, 2007, 5:50 PM CT

Research on Interplay Between Biology and Society

Researchers will find new ways of understanding the interactions of the biological sciences with society, as a result of awards from the National Science Foundation's (NSF) directorates for biological sciences and for social, behavioral, and economic sciences.

The awards are part of the Science and Society Program. They will allow scientists to address current issues, trends and questions relevant to the impacts of biology on society, and vice versa.

Topics to be studied include widely disseminating the letters and other correspondence of Charles Darwin; ways to foster scientific collaboration with Native American communities on issues of sustainability; how populations in Brazil have used scientific information to adapt water systems to climate change; and how concepts of "biodiversity" have changed over time and the impact of these changes on conservation efforts.

The goal of the Science and Society Program is to fund research that examines questions that arise in the interactions of engineering, science, technology, and society. A subset of these awards focuses specifically on the intersections of biology and society.

"Science and researchers don't operate in isolation," said Paul Farel, program director in NSF's directorate for biological sciences. "Their research can have profound implications for the wider world. This program emphasizes that science is an integral part of our social and cultural context"......... Posted by: Janet      Read more         Source

June 27, 2007, 5:48 PM CT

Study Explains Rainforest Similarities

Celebrated in Buddhist temples and cultivated for its wood and cottony fibers, the kapok tree now is upsetting an idea that biologists have clung to for decades: the notion that African and South American rainforests are similar because the continents were connected 96 million years ago.

Research by University of Michigan evolutionary ecologist Christopher Dick and his colleagues shows that kapok---and perhaps other rainforest--trees colonized Africa after the continents split when the trees' seeds traveled across the ocean.

The findings, funded by the National Science Foundation (NSF), appear online this week in the journal Molecular Ecology.

"This research provides vital information for one of the most highly threatened areas of the planet, tropical rainforests," said Sam Scheiner, program director in NSF's Division of Environmental Biology, which funded the research. "In order to plan for and mitigate global climate change, we need to understand the history of life on Earth through studies like this one".

Oceanic dispersal links the world's rainforests, said Dick, "and this study is one of the first to catch that process in action at the species level. Eventhough single seeds are very unlikely to survive an oceanic voyage and then successfully become established elsewhere, such improbable events become probable over 10 to 15 million years"......... Posted by: Erica      Read more         Source

June 27, 2007, 5:45 PM CT

Antarctic Icebergs: Unlikely Oases for Ocean Life

Icebergs have long gripped the popular imagination, whether as relatively run-of-the-mill floating hazards that cause "unsinkable' ships to founder or, more recently, as enormous breakaway pieces of ice the size of states or small countries.

But, as per a paper published in this week's Science magazine, researchers have discovered that these floating ice islands--some as large as a dozen miles across--have a major impact on the ecology of the ocean around them, serving as "hotspots" for ocean life, with thriving communities of seabirds above and a web of phytoplankton, krill and fish below.

The icebergs hold trapped terrestrial material, which they release far out at sea as they melt. Researchers have discovered that this process produces a "halo effect" with significantly increased nutrients, chlorophyll and krill out to a radius of more than 3 kilometers (2 miles).

Based on their new understanding of the role of icebergs in the ecosystem and the sheer number of icebergs in the Southern Ocean--the scientists counted more than 11,000 in satellite images of some 4,300 square miles of ocean--the researchers estimate that, overall, the icebergs are raising the biological productivity of nearly 40 percent of Antarctica's Weddell Sea.

Researchers also have begun to suspect, but argue for additional study, that icebergs may also play a surprising role in global climate regulation by removing carbon from the atmosphere......... Posted by: Janet      Read more         Source

June 22, 2007, 5:02 AM CT

Invertebrate Immune Systems Are Anything But Simple

A hundred years since Russian microbiologist Elie Metschnikow first discovered the invertebrate immune system, researchers are only just beginning to understand its complexity. Presenting their findings at a recent European Science Foundation (ESF) conference, researchers showed that invertebrates have evolved elaborate ways to fight disease.

By studying starfish, Metschnikow was the first to see cells digesting bacteria, a process he called phagocytosis (the eating of cells by other cells). Phagocytosis, it turns out, is an important immune defence in all living things. Since Metschnikow's work, researchers have studied the immune systems of simpler organisms (such as invertebrates) in the hope of understanding the immune systems of more complex organisms, like us.

However, invertebrates' immune systems are more elaborate than we expected. "We have underestimated the complexity of invertebrate immunity," says Dr. Paul Schmid-Hempel, an evolutionary ecologist at the ETH Zurich in Switzerland. By studying the immune systems of fruit flies, mosquitoes and other invertebrates (including bed bugs, moths, crustaceans, worms, sponges and bees), researchers are finding new molecules involved in defences against pathogens (microbes that cause disease).

One molecule found in fruit flies, Dscam, is capable of folding itself in 18,000 different ways. Computer models that predict the structure of this molecule have led researchers to suggest that this folding creates different shapes, each capable of binding to different structures on the pathogen's surface. "These molecules can be used very flexibly by assembling their components in a number of ways," says Schmid-Hempel. Until now, this ability to recognize specific pathogens was believed to be limited to vertebrates......... Posted by: Kelly      Read more         Source

June 20, 2007, 11:06 AM CT

Plant Life On Extrasolar Earthlike Planets

When we think of extrasolar Earth-like planets, the first tendency is to imagine weird creatures like Jar Jar Binks, Chewbacca, and, if those are not bizarre enough, maybe even the pointy-eared Vulcan, Spock, of Star Trek fame.

But researchers seeking clues to life on extrasolar planets are studying various biosignatures found in the light spectrum leaking out to Earth to speculate on something more basic and essential than the musical expertise of Droopy McCool. They are speculating on what kind of photosynthesis might occur on such planets and what the extrasolar plants might look like.

Paint it black

It could be the plants are black, says Robert Blankenship, Ph.D., Lucille P. Markey Distinguished Professor in Arts & Sciences at Washington University in St. Louis. But it all depends on what size and light intensity of star - or sun - the planet feeds off, and the extrasolar planet's atmospheric chemistry.

Plants on Earth are green because of chlorophyll, which harnesses the energy of the sun to make sugars for metabolism. But our plants aren't completely efficient - they waste a little bit of light.

"Ideally, what you want is a black molecule that absorbs all of the light," Blankenship said. "There could be another system developed on an extrasolar planet where plants are completely black if the spectrum of light that's available to organisms is different from the light available to organisms on Earth......... Posted by: Erica      Read more         Source