Caltech Scientists Awarded $20 Million to "Power the Planet"

PASADENA, Calif.--In the dreams of Harry Gray, Beckman Professor of Chemistry at the California Institute of Technology, the future energy needs of the world are met with solar-fuel power plants. Now, a $20 million award from the Chemical Bonding Center (CBC), a National Science Foundation (NSF) Division of Chemistry program, will help bring this dream one step closer to reality.

In 2005, NSF granted three Phase I CBC awards. Gray formed a group of Caltech and MIT scientists who spent the $1.5 million and three years of Phase I conducting initial research and establishing public outreach plans for their idea.

Of the three Phase I projects, Caltech's is the only one to advance to Phase II, a $20 million, five-year extension. "We have added outstanding investigators from many other institutions to our Caltech-MIT team in order to ramp up our efforts in Phase II of the 21st century grand challenge to make solar fuels using materials made from Earth-abundant elements," says Gray.

In Phase I, the Caltech-MIT alliance, called "Powering the Planet," proposed to develop nanoscale materials to make fuel from sunlight and water. They designed a nanorod-catalyst water splitter that incorporates a membrane to separate the oxygen- and hydrogen-making parts of the system.

Nathan Lewis, Caltech's Argyros Professor and professor of chemistry, and chemist Bruce Brunschwig, a Member of Caltech's Beckman Institute (BI) and Director of the Materials Resource Center for the BI, headed a group of students and postdocs who began working on a silicon nanorod-studded plastic sheet to harvest sunlight. The hydrogen-making catalyst team was headed by Gray, Jay Winkler (a Caltech faculty associate in chemistry), and Jonas Peters (a former Caltech chemistry professor now at MIT). Research with the goal of finding efficient catalysts for the oxidation of water to oxygen was led by MIT scientists Dan Nocera, a former graduate student of Gray's, and Christopher Cummins.

With a conceptual design in place, and with promising results in all three investigation areas, the alliance expanded--18 senior researchers at 12 institutions signed on to compete for Phase II of the CBC award and participate in testing and refining the nanoscale water-splitting device.

Luis Echegoyen, Director of the NSF Division of Chemistry, says, "The Division of Chemistry is pleased and excited to establish this new CBC devoted to elucidating some basic science aspects of solar energy research. This center and its excellent team of researchers will enable NSF to partner with the scientific community to explore fundamental aspects of solar-driven splitting of water into hydrogen and oxygen."

The CBC Program is designed to support the formation of centers that can address long-term, high-risk, and high-impact basic chemical research problems. The centers are expected to be responsive to rapidly emerging opportunities and make full use of cyberinfrastructure to enhance collaborations.

"We are excited about our prospects, as we are lucky to have a very talented and dedicated group of students and postdocs who are ready and able to tackle the fundamental chemistry problems that must be solved before it will be feasible to produce clean solar fuels on a large scale," Gray adds. The Phase II award may be extended for an additional five years.

For more information on the award, visit http://nsf.gov/awardsearch/showAward.do?AwardNumber=0802907.

 

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Elisabeth Nadin
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Caltech Scientists Offer New Explanation for Monsoon Development

PASADENA, Calif.--Geoscientists at the California Institute of Technology have come up with a new explanation for the formation of monsoons, proposing an overhaul of a theory about the cause of the seasonal pattern of heavy winds and rainfall that essentially had held firm for more than 300 years.

The traditional idea of monsoon formation was developed in 1686 by English astronomer and mathematician Edmond Halley, namesake of Halley's Comet. In Halley's model, monsoons are viewed as giant sea-breeze circulations, driven by the differences in heat capacities between land and ocean surfaces that, upon heating by sunlight, lead to temperature differences between warmer land and cooler ocean surfaces--for example, between the Indian subcontinent and the oceans surrounding it.

"These circulations form overturning cells, with air flowing across the equator toward the warmer land surface in the summer hemisphere, rising there, flowing back toward and across the equator aloft, and sinking in the winter hemisphere," explains Tapio Schneider, associate professor of environmental science and engineering at Caltech.

A different explanation is offered by Schneider and Simona Bordoni of the National Center for Atmospheric Research in Boulder, Colorado. The duo used a computer-generated, water-covered, hypothetical earth (an "aquaplanet") to simulate monsoon formation and found that differences in heat capacities between land and sea were not necessary. Bordoni was a Moore Postdoctoral Scholar at Caltech and will return to Caltech as an assistant professor in 2009.

Monsoons arise instead because of an interaction between the tropical circulation and large-scale turbulent eddies generated in the atmosphere in middle latitudes. These eddies, which can span more than 300 miles across, form the familiar systems that govern the weather in middle latitudes.

The eddies, Schneider says, are "basically large waves, which crash into the tropical circulation. They 'break,' much like water waves on the beach, and modify the circulation as a result of the breaking. There are feedbacks between the circulation, the wind pattern associated with it in the upper atmosphere, and the propagation characteristics of the waves, which make it possible for the circulation to change rapidly." This can quickly generate the characteristic high surface winds and heavy rainfall of the monsoon.

Bordoni adds: "These feedbacks provide one possible explanation for the rapidity of monsoon onset, which had been a long-standing conundrum in the traditional view of monsoons," because substantial differences between land and sea temperatures can only develop slowly through heating by sunlight.

Although the results won't immediately produce better forecasts of impending monsoons, Schneider says, "in the long run, a better understanding of monsoons may lead to better predictions with semi-empirical models, but much more work needs to be done."

The paper, "Monsoons as eddy-mediated regime transitions of the tropical overturning circulation," appears in the advance online edition of Nature Geosciences. The work was supported by the Davidow Discovery Fund, a David and Lucile Packard Fellowship, a Moore Postdoctoral Fellowship, and the National Science Foundation. The National Center for Atmospheric Research is sponsored by the National Science Foundation. Any opinions, findings and conclusions or recommendations expressed in this publication are those of the author and do not necessarily reflect the views of the National Science Foundation.

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Kathy Svitil
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Chemistry of Airborne Particulate—Lung Interactions Revealed

PASADENA, Calif.--Exactly how airborne particulates harm our lungs still puzzles epidemiologists, physicians, environmental scientists, and policy makers. Now California Institute of Technology researchers have found that they act by impairing the lungs' natural defenses against ozone.

"I've long been perplexed by the inconclusive debates, based on epidemiological and clinical evidence, over whether the causative agent is particle size or some unspecified chemical component. I always felt that some missing chemistry might be associated with particle effects," says A. J. Colussi, a senior research associate in environmental science and engineering at Caltech and author of the study.

The researchers harnessed breakthroughs in chemistry to focus on what happens when air meets the thin layer of antioxidant-rich fluid that covers our lungs, protecting them from ozone, an air pollutant that pervades major cities. "We found new chemistry at the interfaces separating gases from liquids using a technique that continuously monitors the composition of these interfaces," Colussi says.

Adapting an innovation in mass spectrometry by Nobel laureate John Fenn of Virginia Commonwealth University, the Caltech team studied how aqueous ascorbic acid, the essential antioxidant also known as vitamin C and present in lungs' fluid layer, reacts with ozone gas.

Under normal physiological conditions, ascorbic acid instantly scavenges ozone, generating innocuous byproducts. However, the researchers discovered that when the fluid is acidic--a pathological condition found in asthmatics--ascorbic acid instead reacts with ozone to form potentially harmful compounds called ozonides.

"I immediately wondered whether ozonides would injure living tissues," Colussi comments. Indeed, he found literature reports that an ozonide is the active component of a plant extract used in Chinese medicine 2,500 years ago to treat malaria. Synthetic ozonide surrogates are currently used to target the malaria parasite: when the parasite disrupts red blood cells, the reduced iron that is released converts ozonides into cytotoxic free radicals on the spot. The nearby cells that the free radicals damage include the parasite.

The Caltech researchers inferred that inhalation of fine airborne particulates is an essential cofactor for ozonide production. The finer a particle is, the more acidic it is, so when particles are inhaled, they lower the lung pH. Most particulates also carry iron. In the lungs, then, the particularly harmful combination of ascorbic acid, ozone, low pH, and iron should trigger an acute inflammatory response.

To study the conditions that create ozonides, the team conducted experiments in which ascorbic acid solutions are sprayed, converting the liquid into fine droplets. When this mist is crossed by a stream of ozone gas, reactions at the interface of liquid and gas create products that are ultimately ejected from the droplets and then identified by a mass spectrometer.

Fenn had shown why the ions detected by this technique come exclusively from the droplets' interfacial layers, Colussi says. For the Caltech team, the approach provided a means to discover that ozonide yields are markedly enhanced in an acidic setting, when pH falls below five (pH 7 is neutral), and that ozonides are produced at the gas-liquid interface but not in bulk solution.

"Epidemiologists had consistently found significant increases in emergency-room admissions and cardiorespiratory deaths during episodes of high levels of both atmospheric ozone and particulates in several American and European cities, and they didn't know why. Now we have a plausible hypothesis about how ozone and particulates potentiate their harmful effects synergistically," Colussi says. Indeed, the National Academies recently confirmed a link between ozone and premature death.

"This is a chemical breakthrough with wide implications ranging from lung physiology to environmental policy," remarks Colussi. He intends to continue the study in vivo.

"Our tissues, except the stomach, were designed to function at about pH 7," Colussi notes. For example, asthmatics alleviate breathing difficulties by inhaling nebulized bicarbonate solutions at pH 8 to counteract low lung pH just like Tums does for heartburn.

The study appears this week in the early online edition of the Proceedings of the National Academy of Sciences. Other authors are Shinichi Enami, a postdoctoral scholar in environmental science and engineering, and Michael Hoffmann, Caltech's Irvine Professor of Environmental Science and Dean of Graduate Studies. 

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Elisabeth Nadin
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Partnerships of Deep-Sea Methane Scavengers Revealed

PASADENA, Calif.--The sea floor off the coast of Eureka, California, is home to a diverse assemblage of microbes that scavenge methane from cold deep-sea vents. Researchers at the California Institute of Technology have developed a technique to directly capture these cells, lending insight into the diverse symbiotic partnerships that evolved among different species in an extreme environment.

The community's interconnected metabolism sheds light on how the anaerobic microbes, which consume nearly 80 percent of the methane leaked from marine sediments, limit oceanic emissions of this potent greenhouse gas.

"Ninety-nine percent of what's out there we can't grow in the lab, including these methane-oxidizing organisms," says Victoria Orphan, an assistant professor of geobiology at Caltech in whose lab the cell sampling technique was developed.

"We know from ribosomal RNA studies that there is a lot of microbial diversity in nature, but we don't know what the vast majority of microbes are doing," Orphan adds. "We needed a method for separating specific organisms out of complex environments."

Metagenomic analysis, in which the genetic material of all microorganisms swept from their homes in a sample is sequenced wholesale, yields a plenitude of general information. Annelie Pernthaler, a former Caltech postdoc who is now a research scientist at the Centre for Environmental Research in Leipzig, Germany, and Orphan devised a technique to tease out individuals from the diverse microbial community of the deep-sea sediment. Their aim: to simplify the genomic sequencing to target only the organisms they were interested in.

They began with descents in the manned submersible Alvin, collecting cores of sea-floor sediment from areas where methane migrates from below. Back in the lab, the team used enzyme-tagged short DNA probes to specifically bind the ribosomal RNA in the methane-consuming microbes of the sediment. A second reaction used the enzyme to deposit fluorescent molecules within and around the cell, a method known as CARD-FISH, for "catalyzed reporter deposition fluorescence in situ hybridization."

The fluorescing cells and attached microorganisms were captured using microbeads that are both paramagnetic--a form of magnetism occurring only in the presence of an externally applied magnetic field--and coated with an antibody to the fluorescent molecule. This Caltech-patented technique, called "magneto-FISH," bypasses the need to grow the microorganisms in culture because it targets the fluorescing molecules around the cell instead of a specific molecule within the cell.

The cells separated by magneto-FISHing reveal who's partnered up with whom, and provides a fresh look at microbial symbiosis in nature, Orphan says. The main player near the methane vents is a methane-metabolizing member of the Archaea, a prokaryotic domain of life distinct from both bacteria and eukaryotes. Piggybacked on the archaeal cells are some members from among four different species of bacteria--three more than were previously known to be associated with these particular archaea--whose exact roles in the system can now be addressed.

The methane-vent partnership between archaea that consume methane and bacteria that reduce sulfate is believed to be a form of cometabolism or syntrophy, meaning "feeding together," where one species lives off the metabolic products of others. Using the information obtained from the metagenome of these partnerships, says Orphan, biologists can develop specific experiments to directly test the physiological and nutritional relationships between these organisms, as well as the ecological strategies used to successfully colonize deep-sea environments.

One example of such an experiment is highlighted in the group's study, published May 8 in the early online edition of the journal PNAS. The researchers discovered that the organisms possess genes for nitrogen fixation, a process that converts nitrogen gas into nourishing compounds like ammonia. "We were surprised to see these genes in the captured cells," says Anne Dekas, a geobiology graduate student at Caltech, "because we thought these organisms were relatively energy-starved, and nitrogen fixation takes a lot of energy."

Orphan and Dekas were able to show that the organisms are not just equipped for the task, they are actually carrying it out. "Showing nitrogen fixation is a great finding in itself," Dekas comments, "but it is also just one example of the hypothesis testing that can follow magneto-FISH coupled to metagenomic analysis."

Other authors on the study are Caltech's C. Titus Brown, a postdoc in biology; Shana Goffredi, a senior research fellow in environmental science and engineering; and Tsegereda Embaye, a technician in the division of geological and planetary sciences.

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Elisabeth Nadin
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Caltech to Have Largest Solar-Energy Facility in Pasadena

Earth Day is April 22

PASADENA, Calif.-The City of Pasadena's largest-ever solar-energy facility will soon be installed on the California Institute of Technology campus. Construction begins this week and will conclude in August. The facility will be located on top of Caltech's Holliston parking structure.

"This is part of Caltech's commitment to minimizing the Institute's impact on the environment and reducing our dependence on nonrenewable energy," said Caltech President Jean-Lou Chameau.

This facility is expected to have an annual energy production of 320,000 kilowatt-hours. The overall size of the structure is about 220 feet long by 90 feet wide, and it will cover more than half of the top level of the structure.

The remainder of Caltech's energy is supplied by an on-site campus cogeneration plant and by the City of Pasadena. The on-site generation facility provided 77 percent of campus consumption last year. Ultimately, Caltech hopes to add more solar facilities to the campus in an effort to further reduce its reliance on nonrenewable sources.

"The project came about as a result of Caltech's continual focus on the best practices in sustainability and on developing goals and objectives central to renewable energy as a means to save money, foster awareness, reduce environmental consequences of Institute activities, and provide leadership and stewardship relative to the environment," said Dean Currie, Caltech vice president for business and finance.

With these goals in mind, Caltech began construction of a solar-energy facility whose operation will be equivalent to eliminating 527,000 pounds of CO2 emissions from the air each year, removing 46 cars from operation, planting 72 acres of trees, or powering 38 average homes.

The City of Pasadena and Pasadena Water and Power have worked closely with Caltech to create the facility. The city and PWP are providing assistance with expedited permitting, technical support, and substantial rebates to promote renewable energy development in Pasadena. Design and construction will be completed by EI Solutions, a subsidiary of Energy Innovations of Pasadena. The project will be financed and operated through a Power Purchase Agreement between the campus and Solar Power Partners of Mill Valley, California.

"We're thrilled to be building a solar facility at Caltech and to be a part of the Institute's plans to reduce its impact on the environment and dependence on nonrenewable energy," said Andrew Beebe, president of EI Solutions. "Caltech is a leader in so many areas, and it is great to see it setting an example for universities and corporations across the country that are looking for ways to utilize economically sound green-energy alternatives like solar."

The solar-energy facility is one of many sustainability efforts the Caltech campus has undertaken in recent years. In addition to the previously mentioned cogeneration plant on campus, dining facilities use compostable food containers, incandescent lightbulbs are being switched to compact fluorescent bulbs, grounds planners use water-wise landscaping, there is a "green" cleaning program used by the custodial staff, an award-winning recycling program accepts items from the campus and local community, and the Caltech Electric Vehicle Club has a few electric cars that qualified users are free to drive.

Caltech is constructing three new buildings that will receive gold Leadership in Energy and Environmental Design (LEED) ratings. This means the buildings will reduce their impact on the environment through energy and water efficiency and materials conservation, among other characteristics.

"We take a lot of pride in what we have accomplished to date, but we are even more excited about what the future holds," said Bill Irwin, senior director of facilities management at Caltech. "We plan to add more solar facilities in the near future, to produce up to an additional megawatt of power. We are looking for innovative ways to reduce water usage through sustainable planting and turf reduction and by capturing and reusing wastewater from our boilers. Caltech recently installed two high-efficiency water chillers and will install more this year, along with other energy-efficient equipment upgrades. These are just a few examples of current and future plans. We recognize that what we are doing today and will do tomorrow directly affects those who will come after us, and we would like to leave a positive legacy."

For a more comprehensive list of "green" initiatives at Caltech, go to the Sustainability at Caltech website at http://sustainability.caltech.edu/.

About Caltech With an outstanding faculty, including five Nobel laureates, and such off-campus facilities as the Jet Propulsion Laboratory, Palomar Observatory, and the W. M. Keck Observatory, the California Institute of Technology is one of the world's major research centers. The Institute also conducts instruction in science and engineering for a student body of approximately 900 undergraduates and 1,300 graduate students who maintain a high level of scholarship and intellectual achievement. Caltech's 124-acre campus is situated in Pasadena. Caltech is an independent, privately supported university. On the Web at http://www.caltech.edu/

About EI Solutions EI Solutions is one of California's fastest-growing providers of commercial and utility-scale solar power systems. The company has completed projects for a wide variety of public agencies and private companies including Sony, BT, and the largest solar installation on a U.S. corporate campus, a 1.6 megawatt system on Google's Mountain View headquarters. EI Solutions' headquarters are in San Rafael, California, where all engineering, project management, finance, and administrative functions are based. EI Solutions also operates a sales and marketing office in Pasadena, at the home of its parent company, Energy Innovations. Energy Innovations, an Idealab company, is a manufacturer of commercial solar products that maximize usable energy from the sun. More information can be found at http://www.eispv.com or by calling 800.237.0916.

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Jill Perry
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Caltech Creates New Center to Study the Global Environment

PASADENA, Calif.- To address the complex issue of global climate change from a wide range of disciplines, Ronald and Maxine Linde have established an $18 million endowment for the California Institute of Technology to create the Ronald and Maxine Linde Center for Global Environmental Science, uniting faculty from chemistry, engineering, geology, environmental science, and other fields.

The problems addressed by global environmental science represent the types of multidisciplinary challenges for which Caltech is well suited. Approaching them requires close collaboration among all six of Caltech's academic divisions--from chemists studying ozone-destroying reactions in the stratosphere, to fluid dynamicists and physicists studying atmospheric and oceanic flows, to biologists studying nutrient cycles, to geologists studying evidence of the effects of past climates, to social scientists (including economists) and humanists evaluating how society and institutions can respond to global change. In addition, Caltech's Jet Propulsion Laboratory (one of the nation's leading centers for satellite-based observation of the atmosphere, oceans, and land surface) can characterize and monitor changes in the current environment.

"Ron and Maxine Linde appreciate how critical environmental science is to the future of life on our planet and the tremendous contributions the Caltech faculty can make to society," says Caltech president Jean-Lou Chameau. "Their gift will help bring our faculty together and provide flexible support that is critical to creative thinking."

Funded by the Lindes, the initiative will help Caltech achieve its vision of having an integrated program in global environmental science, spanning the many disciplines that must make up such a program. Edward Stolper, Caltech's provost, explains that the Linde Center "will provide a central home and focus for researchers and students working on understanding natural variations in and the impact of human activity on the global environment. These are among the most important and most difficult problems facing our society, and this gift will help Caltech play an important role in addressing them."

To train the future generations of scientists and engineers who will address these problems, Caltech recently established a degree-granting program in environmental science and engineering. This interdivisional program offers training and research ranging from a large-scale understanding of the ocean/atmosphere system and climate to the local scale of developing engineering solutions for environmental problems. As pointed out by Stolper, "Few programs have taken this step of bridging global environmental science and conventional environmental engineering--yet it is an approach we believe will be critical to training future leaders."

The faculty and students associated with the program will be housed in the 75-year-old building that is currently the Henry M. Robinson Laboratory of Astrophysics. When renovated, the building will be named the Linde + Robinson Laboratory. The astronomers will move a short distance to the soon-to-be-completed Cahill Center for Astronomy and Astrophysics.

Ronald Linde has been a Caltech trustee since 1989. He is a private investor and chairman of the Ronald and Maxine Linde Foundation, a private foundation that the Lindes established in 1989. He was founder, chairman, and CEO of Envirodyne Industries Inc. He also held various scientific research and management positions at Stanford Research Institute (now SRI International) and has authored or co-authored more than 50 publications in science and technology. He received a bachelor of science degree in engineering from UCLA and master's and PhD degrees in materials science from Caltech.

Maxine Linde is a private investor and president of the Ronald and Maxine Linde Foundation. She was involved in the early U.S. space program as a scientific programmer at JPL and subsequently served as Envirodyne's general counsel and chief administrative officer. She received a bachelor of arts degree in mathematics from UCLA and a JD degree from Stanford Law School.

The Lindes have established the Ronald and Maxine Linde Professorship of Applied and Computational Mathematics at Caltech, currently held by renowned mathematician Emmanuel Candes. They also have funded a challenge grant to create the Ronald and Maxine Linde/Caltech Alumni Laboratories in Caltech's Broad Center for the Biological Sciences.

 

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Jill Perry
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Caltech Joins National Global-Warming Teach-In

PASADENA, Calif.--Did you know that it takes about the energy found in 1.4 liters of gasoline to make a cheese pizza? The energy cost of producing food is one focus the California Institute of Technology will take as it participates in a nationwide effort to engage schools in global-warming solutions.

On Wednesday and Thursday, January 30–31, Caltech will join more than 1,100 universities across the country for an unprecedented teach-in organized by Focus the Nation.

Focus the Nation is an initiative to draw attention to global warming through a teach-in that will engage faculty, students, staff, and community members. It is centered on what they consider to be the three most essential pillars needed for today's youth to embrace solutions to global warming: education, civic engagement, and leadership. Organizers chose the January date because it coincides with the beginning of the 2008 primary election season. They intend to stir a nonpartisan national discussion about confronting the challenge of climate stabilization.

Among the coordinators for Caltech's participation are graduate students Morgan Putnam and Asa Hopkins and undergraduate Aryan Safaie. Hopkins was inspired to host the event after hearing a speech by Focus the Nation project director Eban Goodstein at a campus sustainability conference at UC Santa Barbara last summer. Goodstein is an economics professor at Lewis and Clark College in Portland, Oregon, who took a two-year hiatus from teaching to champion this cause.

The teach-in officially kicks off at 8 p.m. on January 30 in Beckman Institute Auditorium with a live, interactive webcast of "The 2% Solution", in which climate scientists and experts in related fields will discuss global-warming solutions and tackle viewers' questions. The title of the webcast reflects the idea that developed countries must cut roughly two percent of their current emissions per year in order to arrest global warming at an ultimate minimum of around four degrees Farenheit.

At lunchtime on January 31, the Caltech chapter of the Engineers for a Sustainable World invites the campus and community to join the Focus the Nation effort with an angle on food choices. They will provide fliers to inform lunchtime patrons at Chandler Dining Hall about where their food originates, the energy it takes to provide the meals, the environmental consequences of growing and buying food, and suggestions for minimizing impact.

Among other options, diners can select locally-caught fish topped with a salsa concocted from grapefruit from the backyard of Caltech president Jean-Lou Chameau and California-grown kiwi and blood oranges, with a side of California-grown broccoli and cauliflower. The event organizers will also sponsor a contest that quizzes consumers about energy-related food choices. Which is the most energy-efficient option: a cardboard pizza box, a porcelain plate, or a compostable plate? The winner scores free pizza for a week.

"Focus the Nation gives us a coordinated chance to broaden the conversation at Caltech. Often we're very research focused, and that's good, but we also need to remember that our actions outside of the lab matter, too," comments Hopkins.

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Elisabeth Nadin
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Genetic Underpinnings of Wood Digestion by Termite Gut Microbes Revealed

PASADENA, Calif.--When termites are chewing on your home, your immediate thought probably isn't "I wonder how they digest that stuff?" But biologists have been gnawing on the question for more than a century. The key is not just the termite, but what lives in its gut. A multitude of genes from the microbes populating the hindgut of a termite have been sequenced and analyzed, and the findings reported today in the journal Nature.

California Institute of Technology associate professor of environmental microbiology Jared Leadbetter led a team of researchers from other universities, private industry, and the Department of Energy (DOE) in uncovering the genetic underpinnings and the roles of bacteria in wood digestion by "higher termites." These insects abound in tropical and subtropical ecosystems. What the team found, says Leadbetter, is "a comprehensive set of blueprints for the bacteria that help dismantle wood."

Prior to this study, only one gene--in the insect itself--had been connected to the termite's rare ability to digest and nourish itself with wood, a substance that is energy-rich but hard to break down. It had also long been suspected that the 250 bacterial species that crowd the pinhead volume of a higher termite's hindgut might be directly involved in the process. But there was no way of knowing their roles for sure, because most of the organisms die quickly when removed from their host. Although the first bacterium genome was sequenced in 1994, it was a few years before scientists even considered sequencing entire communities of multiple species of organisms.

Leadbetter and his colleagues proposed to the DOE Joint Genome Institute (JGI) that the gut community of the Costa Rican termite Nasutitermes be examined because it is abundant and it plays significant roles in the wood degradation that helps to renew ecosystems. Leadbetter joined forces with collaborators at JGI, Verenium Corporation's San Diego facilities, and INBio, the National Biodiversity Institute of Costa Rica. They sequenced and analyzed more than 80,000 genes encoded by many of the hindgut bacteria species. "This was a fairly risky project when we proposed it," says Leadbetter, because "in these abundant tropical termites, there was no compelling evidence that these microbes play direct roles in cellulose degradation."

When the results started coming in, "we all breathed a big sigh of relief, because it turned out to be a gold mine in there," Leadbetter says. They found nearly 1,000 genes that underlie roles in breaking down two of wood's main components, cellulose and xylan, into their component sugars. The degradation of cellulose and xylan requires an arsenal of enzymes because of the huge diversity of biochemical bonds in wood. "This isn't some soft paper or grass we're talking about," says Leadbetter. "It's a hard substrate." Wood is made of three tightly intertwined compounds; taking it apart is a challenge, and termites are among the few known animals that can do it.

Leadbetter and his colleagues hope to eventually uncover exactly how each gene is involved in degrading wood, and where the energy the termite derives from the wood goes. This has recently become a focus of interest for those interested in developing an effective, industrial method to convert wood into ethanol. The challenge lies in events at the start of the process, like those involved in breaking down cellulose and xylan. Leadbetter and his colleagues believe that by investigating the genes that underlie these primary reactions, better ways of manufacturing biofuel can eventually be developed.

The study also identified nearly 100 different species of bacteria called spirochetes that belong to the genus Treponema. This membership makes them closely related to the bacterium that causes syphilis and to other spirochetes implicated in Lyme disease and gum disease. In termites, though, the findings show that these spirochetes actually benefit the health of their hosts. The genome sequencing also showed that the spirochetes are active in processes that generate hydrogen, an energy-rich gas, from wood. Certain genes also indicate that gut spirochetes can essentially taste or smell hydrogen and will swim either to or from its sources in the gut. In general, Leadbetter says, it looks like "these bacteria differ from those that dominate the gut tracts of humans and other mammals in their broad capacity to swim in response to diverse chemical stimuli. This behavior may be relevant to effective wood degradation."

Other Caltech authors of the paper are Eric Matson, a postdoctoral scholar in environmental science and engineering; Xinning Zhang, a graduate student in environmental science and engineering; and Elizabeth Ottesen, a graduate student in biology. Group leaders are Dan Robertson of Verenium Corporation, Phil Hugenholtz of the JGI, Giselle Tamayo of INBio, and Eric Mathur, formerly of Diversa (now at Synthetic Genomics).

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Elisabeth Nadin
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New Method of Studying Ancient Fossils Points to Carbon Dioxide As a Driver of Global Warming

PASADENA, Calif.—A team of American and Canadian scientists has devised a new way to study Earth's past climate by analyzing the chemical composition of ancient marine fossils. The first published tests with the method further support the view that atmospheric CO2 has contributed to dramatic climate variations in the past, and strengthen projections that human CO2 emissions could cause global warming.

In the current issue of the journal Nature, geologists and environmental scientists from the California Institute of Technology, the University of Ottawa, the Memorial University of Newfoundland, Brock University, and the Waquoit Bay National Estuarine Research Reserve report the results of a new method for determining the growth temperatures of carbonate fossils such as shells and corals. This method looks at the percentage of rare isotopes of oxygen and carbon that bond with each other rather than being randomly distributed through their mineral lattices.

Because these bonds between oxygen-18 and carbon-13 form in greater abundance at low temperatures and lesser abundance at higher temperatures, a precise measurement of their concentration in a carbonate fossil can quantify the temperature of seawater in which the organisms lived. By comparing this record of temperature change with previous estimates of past atmospheric CO2 concentrations, the study demonstrates a strong coupling of atmospheric temperatures and carbon dioxide concentrations across one of Earth's major environmental shifts.

According to Rosemarie Came, a postdoctoral scholar in geochemistry at Caltech and lead author of the article, only about 60 parts per million of the carbonate molecular groups that make up the mineral structures of carbonate fossils are a combination of both oxygen-18 and carbon-13, but the amount varies predictably with temperature. Therefore, knowing the age of the sample and how much of these exotic carbonate groups are present allows one to create a record of the planet's temperature through time.

"This clumped-isotope method has an advantage over previous approaches because we're looking at the distribution of rare isotopes inside a single shell or coral," Came says. "All the information needed to study the surface temperature at the time the animal lived is stored in the fossil itself."

In this way, the method contrasts with previous approaches that require knowledge of the chemistry of seawater in the distant past--something that is poorly known.

The study contrasts the growth temperatures of fossils from two times in the distant geological past. The Silurian period, approximately 400 million years ago, is thought to have been a time of highly elevated atmospheric CO2 (more than 10 times the modern concentration), and was found by the researchers to be a time of exceptionally warm shallow-ocean temperatures—nearly 35 degrees C. In contrast, the Carboniferous period, roughly 300 million years ago, appears to have been characterized by far lower levels of atmospheric carbon dioxide (similar to modern values) and had shallow marine temperatures similar to or slightly cooler than today-about 25 degrees C. Thus, the draw-down of atmospheric CO2 coincided with strong global cooling.

"This is a huge change in temperature," says John Eiler, a professor of geochemistry at Caltech and a coauthor of the study. "It shows that carbon dioxide really has been a powerful driver of climate change in Earth's past."

The title of the Nature paper is "Coupling of surface temperatures and atmospheric CO2 concentrations during the Paleozoic era." The other authors are Jan Veizer of the University of Ottawa, Karem Azmy of Memorial University of Newfoundland, Uwe Brand of Brock University, and Christopher R. Weidman of the Waquoit National Estuarine Research Reserve, Massachusetts.

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Robert Tindol
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Some Earth-like Worlds May Have Foliage of Colors Other Than Green, Researchers Say

PASADENA, Calif.—In the next decade, when scientists are able to study Earth-sized worlds around other stars, they may find that foliage on some of the planets is predominantly yellow—or orange, or red. It all depends on the color of the star the planet orbits and the stuff that makes up the planet's atmosphere.

That's the conclusion of researchers from the Virtual Planetary Laboratory, a NASA-funded initiative at the California Institute of Technology, who are announcing today results from a series of comprehensive computer models for guiding the future search for plant life on other worlds. Two related papers on what to expect out of photosynthesis are being issued in the journal Astrobiology.

Determining the range of possible colors is important because scientists need to know what to look for when they begin getting spectra of light from faraway Earth-sized planets, says lead author Nancy Kiang, a biometeorologist at NASA's Goddard Institute for Space Studies, and currently a visitor at Caltech's Spitzer Science Center.

"The dominant color of photosynthesis could be yellow, or orange, or maybe red," Kiang explains. "I think it is unlikely that anything will be blue—and, of course, green plants are also a possibility, since that's what we have here."

"What makes this study unusual is the highly interdisciplinary method by which planetary scientists, atmospheric scientists, biologists, and others have pooled their efforts in modeling the possible spectra of light available to plants on Earth-like planets orbiting around other stars," says Vikki Meadows, an astrobiologist at Caltech and lead scientist of the Virtual Planetary Laboratory. Because the study requires data about everything from the type of photons given off by a main-sequence star in a particular stage of its life, to the depth of water that an aqueous plant might prefer, a huge variety of information is required.

"No single astronomer or biologist or atmospheric scientist could have attacked this problem individually to get the simulation," says Meadows, who is herself an astrobiologist whose original academic training was in astronomy. "So these papers are truly interdisciplinary pieces of work."

The researchers focused on the way plants use light for energy to produce sugar—which is pretty much the definition of photosynthesis—because photosynthetic pigments must be adapted to the available light spectrum. The available light spectrum at a planet's surface is a result of both the light from the parent star and filtering effects of gases in the atmosphere. For example, ozone absorbs ultraviolet light, so that not much reaches Earth's surface.

"It turns out that the spectrum of the number of particles of light is what is important, and on Earth there are more particles in the red," Kiang explains. "This could explain why plants here on Earth are mainly green."

On Earth, plants absorb blue light because it is energetic, and red light because the photons are plentiful. There is more than enough energy from the blue and red in sunlight, so plants do not really need more. Therefore, they reflect away relatively more green light, which is why plants appear green to us.

A planet orbiting a star with the size and temperature roughly like our sun, and with Earth's particular mix of oxygen and what-have-you, would tend to have plants that like to soak up light in blue and red and less in green. But the situation could be different on other planets, where other colors of the spectrum might predominate. In those cases, another color like red might not be so useful, and the plants would mostly appear red.

There are many other factors, such as the role not only ozone plays but also carbon dioxide and water vapor, how the stellar radiation creates chemical reactions in the atmosphere, whether the star is prone to solar flares, how much water is on the planet, how much light gets to the surface, what gases are produced by the plants themselves, and so on. This is why a complex computer model was necessary.

Also, one might wonder what things could live on a planet with very little ozone, for example, where radiation would be a daily assault on living organisms, and energetic particles from solar winds would be like deadly microscopic bullets. Meadows says the modelers have taken such scenarios into consideration, and they think that there might be a "sweet spot" a few to tens of feet below the surface of the water where life is protected from UV radiation.

"We found that the sweet spot could be up to nine meters underwater for a planet orbiting a star significantly cooler than our sun, and photosynthesis could still take place," she says. "Something with a floatation capability could be protected from solar flares and still get enough photons to carry on."

In short, the new model provides a powerful tool for looking for life on other worlds, Meadows says.

"We once thought that planets around other stars were exceedingly rare," she explains. "But every time telescopes have gotten better, we've been able to find more and more Jupiter-sized planets. So there's no reason to think that there aren't a huge number of Earth- sized planets out there as well.

"We may not find anything like ourselves, but it's possible that bacterial life is prevalent on these Earth-like planets," Meadows adds. "If we have the environment for life to exist, then we think that it's likely that life will emerge in these conditions."

The other authors of the two papers are Antigona Segura-Peralta, Giovanna Tinetti, Martin Cohen, Janet Siefert, and David Crisp, all of the Virtual Planetary Laboratory, Govindjee, of the University of Illinois, and Robert Blankenship, of Washington University.

The Virtual Planetary Laboratory was formed as part of the NASA Astrobiology Institute, which was founded in 1997 as a partnership between NASA, 12 major U.S. teams, and six international consortia. NAI's goal is to promote, conduct, and lead integrated multidisciplinary astrobiology research and to train a new generation of astrobiology researchers.

For related images, please visit

http://www.nasa.gov/centers/goddard/news/topstory/2007/spectrum_plants.html.

 

 

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Robert Tindol
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