SOLS News

Mineral studies advance antibacterial alternatives

kakeane — Fri, 12 Mar 2010 13:30:47 -0700

ASU School of Life Sciences undergraduate Jenny Koehl and microbiologist Shelley Haydel investigate the chemistry and killing power of clays with antibacterial activity.

by Margaret Coulombe

Alternative approaches to medicine are stock-in-trade in the ASU laboratory of microbiologist Shelley Haydel.

So when ASU senior Jenny Koehl joined Haydel’s investigative team seeking firsthand knowledge of how basic research is done, how drugs are tested and potential cures produced, she found it and much more.

With the guidance of Tanya Cunningham, a graduate student mentor, Koehl has helped advance understanding about the antibacterial activity of clay minerals and their ability to kill what the best antibiotics on the market can’t touch.

Haydel’s group collaborated with Jack Summers, an inorganic chemist at Western Carolina University. They uncovered two factors that control the antibacterial activity. Their work was published in the March 1 issue of Public Library of Science (PLoS) ONE.

“This work sets a baseline from which to look for potential mechanisms of antibacterial action,” said Cunningham, lead author, who is now a research technician with the Fred Hutchinson Cancer Research Center in Seattle.

“We need helpful alternatives, natural approaches to antibacterial cures, because there is bacterial resistance to drugs,” Koehl said. “Knowing the mechanisms of action will help us develop our own topical treatments.” Clay has had a role in human health as ancient as man. However, specific identification of the mechanisms underlying this antibacterial activity has been elusive, until now.

The Haydel-Summers collaborative has added clarity to these distinctly muddy waters by screening more than 50 mineral mixtures (and aqueous extractions from them, known as leachates) marketed as health and cosmetic products using pathogens Escherichia coli, Salmonella enterica serovar Typhimurium, Staphylococcus aureus, methicillin-resistant S. aureus (MRSA), and Pseudomonas aeruginosa. Only two mineral mixtures of significantly different compositions (and their leachates) were discovered to possess antibacterial traits.

Clay minerals often are recognized as the slimy slurry that slicks riverbanks. Understanding clay’s structure is integral to answering questions about the mechanisms behind its antibacterial activity. Negatively charged surfaces attract positively charged elements, such as iron, copper, silver and other metals. In turn, water is absorbed between layers of the crystal structure creating a cation sandwich with aqueous filling or interlayer. Antibacterial activity in leachates, extracted from the mineral mixtures, confirm that the antibacterial activity is chemically-based, rather than a result of physical interactions with microbes.

Because of the tendency of clay to attract multivalent ions, particularly metals, the scientists next examined the leachates’ chemistry and antibacterial activity in the presence of chelators, which bind metals. The researchers also used thiourea, a hydroxyl radical scavenger, at various pH levels. Chelation of the minerals with ethylenediaminetetraacetic acid (EDTA) or desferrioxamine eliminated or reduced toxicity, respectively.

Further testing of the mineral leachates confirmed that there are higher concentrations of chemically-accessible metal ions in leachates from antibacterial samples than from non-bactericidal mineral samples.

In addition, acidic conditions were found to increase the availability of metal ions and their toxicity. Overall, these findings suggest a role of an acid soluble metal species, particularly iron or other sequestered metal cations, in mineral toxicity. However, whatever advances the study puts forward also present researchers with further challenges. Acidity may complicate development of topical treatments, if neutral pH, least damaging to skin and tissue, also reduces the mineral’s antibacterial action.

Another complicating factor is that chemical environments under which any particular clay can emerge can greatly influence its toxicity, adsorptive qualities and, according to their findings, its antibacterial effects.

“Because natural mineral mixtures can be variable, both mineralogically and chemically, we must continue to define specific chemical properties that influence the antibacterial effectiveness,” Haydel said. “Our goal is to understand the details, so we can, in the future, perhaps generate mineral mixtures that mimic the chemical compositions and environment, so that the antibacterial activity can be controlled and ensured.”

This work is about eliminating the unknowns,” Koehl said. “We have more analysis to do, looking at the leachate composition, the action of the chelators and activity of the iron scavengers.”

Koehl, who is working with Haydel as part of the School of Life Sciences Undergraduate Research (SOLUR) program, said of her experience: “Science is like an obstacle course. I’ve learned that when you come across problems in the laboratory, you have to be creative to work them out. This process has helped me be more critical, to be a thinking scientist, because I’ve had to analyze my own experiments and figure them out. This isn’t just something that someone handed to me on paper in a classroom.”

Studies are moving forward in other laboratories to develop structured clays for slow-release topical medical treatments, but there may be chemical schemes that come from Haydel’s research that enhance their effectiveness.

“This study has given me an idea of how things move from idea to shelf,” Koehl said. “One day, when I am a pharmacist, maybe I’ll be selling this!”

This work is supported by the National Institutes of Health. Haydel’s group is part of the School of Life Sciences, in the College of Liberal Arts and Sciences, and the Biodesign Institute at ASU.

Read the article in PLoS ONE.

‘HUNTing’ skills lead to bio-inspired solutions

dianeb — Wed, 06 May 2009 12:50:17 -0600

by Margaret Coulombe

Hungry lions on the savanna or porpoises in the sea work as teams to catch prey. Schooling fish dart in unison to escape a predator. Even “Meerkat Manor” depicts complex groups with clearly defined duties. What do these complex activities all have in common? For Stephen Pratt, assistant professor in Arizona State University’s School of Life Sciences, they represent different aspects of the hunt, but in ways that most people could barely begin to imagine.

ASU and Pratt hosted engineers, computer scientists, biologists and social scientists at a recent workshop—Heterogeneous Unmanned Networked Teams (HUNT)—that focused on developing bio-inspired solutions to engineering problems.

The workshop is part of a five-year project of the same name funded by the Office of Naval Research (ONR). The effort is led by 10 engineers and computer scientists from the University of Pennsylvania, University of California, Berkeley, and the Georgia Institute of Technology, in addition to ASU’s Pratt, who is the sole biologist in the group.

Why would naval research and other engineering research institutions look to nature for bio-inspired solutions? “Robustness, scalability, and the ability to function without complex central control are things that are really desirable in an artificial system,” Pratt points out. “All kinds of natural systems have them; from the movement of fish in schools and birds in flocks to social insects building specific, complex nest structures.”

“One of ONR’s long-term grand challenges is how to deal with the interaction of large numbers of fairly sophisticated autonomous vehicles—flying drones, vehicles underwater or on land,” Pratt explains. “All kinds of increasingly diverse and complex artificial systems will have to interact with each other and with humans.”

Military applications present particular challenges because of the large numbers of people, machines and unpredictable situations.

Photo by Karl Hedrick/Center for the Collaborative Control of Unmanned Vehicles

However, the engineering product is more likely to be a focus towards the end of the project, Pratt says. In the meantime, the workshop was all about thinking outside the box and creating an atmosphere for a rapid exchange of ideas.

Some of the more than 20 consultants attached to the project, spanning the fields of engineering, social sciences and biology, joined the project leaders at the workshop held March 9-10 at ASU. The goal was to pair up particular complimentary problems from biology and engineering.

For example, James Rehg and Tucker Balch of Georgia Tech are using their expertise to design automated computer vision systems to track films of animals in nature—namely, lion teams hunting—and be able to recognize and classify the behavior of each individual. This will enable African savanna ecologist Craig Parker of the University of Minnesota to get large quantities of data efficiently and empower him to ask questions about the coordination of group behavior over long time periods. Previously, this could only be done by painstakingly analyzing months of footage.

“Rehg, Balch and their research groups are really interested in doing this kind of thing—partly because it helps them study their own artificial collective systems by testing the ability of their system to analyze complex biological data,” Pratt says with a knowing smile. “Also, they like the idea of a really challenging computer vision problem; they get to do something new and different with our data.”

Another pair of researchers, Lori Marino of Emory University, an expert on porpoise teamwork, and Magnus Egerstedt of Georgia Tech, a robotics engineer, are delving into what porpoises do when they encircle prey. Porpoises are of particular interest because they are very good at switching team strategies quickly to meet changing circumstances. Egerstedt hopes to develop control algorithms for artificial systems that can effect the same sorts of rapid functional changes. Eventually these algorithms could be used to control groups of underwater or fleets of flying vehicles.

Pratt’s first taste of this “HUNTsian” type of collaborative endeavor came when he was asked to be a part of SWARMS (Scalable sWarms of Autonomous Robots and Mobile Sensors) an invitation based on his innovative research on collective decision making in acorn ants. Pratt clarifies, “SWARMS was directed at what could be learned from natural systems with many animals; where all the individuals are simple—maybe even a little bit stupid. Imagine a swarm of army ants.”

The naval research project steps up the complexity in problem-solving, focusing on smaller groups of organisms, each with a unique position and attribute. “The HUNT project leaders originally thought exclusively about vertebrates,” Pratt says. “But, I convinced them that ants carry out tasks which are much more sophisticated than they had initially thought.”

Picture this, Pratt says: “A single ant finds a tasty fig piece (left by a scientist) in an open desert patch. Alone, she cannot rescue the piece from a larger competitor; but wait, five sisters arrive, each picks up a side and together they negotiate this morsel—many times larger than themselves—over a tough terrain and back to the nest. Dinner is served. In order to accomplish this task, the ants must work as a team, each one with a unique job: guiding, spinning or doing the heavy lifting.”

Pratt teams up with Vijay Kumar, with the University of Pennsylvania, to address this issue of collective retrieval: a big problem in collective robotics. “I’m getting the biological data; they’re devising tools that I would never be able to make. For example, force sensors that we try to get the ants to carry with them,” says Pratt.

“What I take away is a much more detailed description and measurement of what these insects are actually doing. What they get is inspiration for programming their robots to do the parallel task,” he says.

In some ways, the HUNT teams are analogous to their project, with each member playing a unique and essential role. Alone, each individual might be slow or lack efficiency in carrying the proverbial fig, but by combining their distinctive expertise, together they make one extraordinary, bio-inspired problem-solving team.

Media Contact:
Margaret Coulombe
(480) 727-8934
margaret.coulombe@asu.edu

Ants have a failsafe cheater-detector

ovprea — Tue, 13 Jan 2009 12:03:28 -0700

by Margaret Coulombe

A cheater, given away by fertility hydrocarbons, is bitten by nestmates during policing. (Photo by Adrian Smith)

An 'honest indicator' has been discovered by a scientific team at Arizona State University that reveals reproductive cheating. But before you run out to buy an infidelity identification kit, know that it only works for ants.

While it's well-known that workers in ant colonies typically support one reproductive female—a queen, it turns out that cheating can be a problem, and not just for humans. Cheating is found in all sorts of animal and insect groups, including other highly organized social organisms, such as ants.

Humans cheat on their partners roughly 15-18 percent of the time (according to scientific studies), however, worker ants that stray from acceptable celibate social norms rarely, if ever, are successful. Cheaters are actively weeded out by other workers, and brought back into line, through a process called policing.

How can workers in an ant colony, with hundreds to thousands of sister-workers around them, locate one cheater in an ant hill?

Through fertility hydrocarbons, says Jürgen Liebig, an assistant professor in the School of Life Sciences and member of the Center for Social Dynamics and Complexity in ASU's College of Liberal Arts and Sciences.

According to research findings published in the journal Current Biology on Jan. 8, hydrocarbons on the outside cuticle of fertile ants form "a particular chemical signature blend." It is a cocktail that an ant apparently can't deny, cover up, or lie about and which brands a cheater much like the red "A" on the bosom of Hester Prynne in Nathaniel Hawthorne's The Scarlet Letter.

Social insects, such as ants, bees and wasps, rely heavily on chemical signals to communicate. While earlier studies indicated that chemical signatures are associated with fertility, it was ASU doctoral student Adrian Smith's studies with Aphaenogaster cockerelli worker ants that established that these chemical signatures are what allow workers to locate and police cheaters. To do this, Smith painted a non-fertile (non-cheating) worker with a potent pentocosane (hydrocarbon), making her a reproductive mimic. When Smith placed the ant back within her colony, fellow workers sniffed out the "cheater," biting and attacking her.

"While we knew for some time that fertility status in ants was correlated with particular blends of hydrocarbons on the surface of the cuticle, no one was able to demonstrate that this hydrocarbon blend served as an indicator of fertility status to other nest mates," says ASU's Bert Hölldobler, Pulitzer Prize winning author of The Ants, coauthored with Harvard Professor Emeritus Edward O. Wilson.

A second set of experiments confirmed the group's findings. In an ant colony that lacked a queen, and in which some workers were reproducing, colony members had no aggressive response to the chemically altered, fake fertiles.

"This discovery is strong evidence that these hydrocarbons are 'honest indicators,' meaning their expression on the cuticle is intimately coupled with the physiological processes that regulate fertility status," says ölldobler, a professor in ASU's School of Life Sciences.

Fertility is signaled through hydrocarbon signatures on both the eggs and the cuticle of a worker ant. An A. cockerelli worker ant's egg has the same fertility signal as the queen.

According to Smith, these hydrocarbons serve as a red-flag to other workers, announcing: "This one is capable of laying viable eggs." Since egg surface hydrocarbons and cuticular hydrocarbons are physiologically linked, a change in one results in a change in the other.

Why are the hydrocarbons then especially suited to prevent reproductive cheating? Research shows that the chemicals don't lie and worker ants cannot eliminate them to escape detection.

In order to be successful cheats, reproductive workers need to escape being identified. Yet, they still need to assure that their eggs escape detection. Hiding their eggs in plain sight, amongst those of the queen, would be the easiest solution. However, to achieve this, the worker's eggs would need to express the fertility signal, like those of the queen.

"The dilemma is that if you do not produce the fertility signal on the cuticle you can escape detection, but if you don't produce it on the egg, it won't escape detection," Liebig explains. "This seems to make cheating impossible, since they cannot solve both problems at the same time."

The idea that ant colonies stabilize their social structure by maintaining a system for punishing miscreants, with a built-in mechanism for reliably identifying individuals as cheaters, is where work such as Smith, Hölldobler and Liebig's finds application in other systems.

All animal societies share the common problem of individuals exploiting group resources for personal gain at a cost to the group. Smith points out that trying to understand how ant societies deal with this problem "gives us a basis for looking into the mechanisms used by other successful societies."

"This paper opens a new window in our understanding of the social regulation and evolution of reproductive division of labor, a key trait in eusocial insects," adds Hölldobler. In addition to this collaborative work, which will be highlighted in the journal Nature, Hölldobler's nearly half-century study of insect societies has created a proliferation in many new areas of discovery. A book will be released in his honor by Harvard Press in February 2009, Organization of Insect Societies: From Genome to Sociocomplexity.

Designer ecosystems have unintended consequences

ovprea — Mon, 08 Sep 2008 14:41:02 -0600

by Margaret Coulombe

Amidst the semi-arid stretches of Phoenix, a visitor might blink twice at the sight of a sailboat cutting across the horizon. Tempe Town Lake, on the northern edge of Arizona State University, is just one of a multitude of lakes, small ponds, canals and dams combining flood control, water delivery, recreational opportunities and aesthetics, and altering perception of water availability and economics in the area.

Tempe Town Lake

What are the consequences of such human-made tinkering with land cover and hydrology on surrounding native ecosystems and biodiversity? This question forms the backdrop for a case study proffered by an ASU research team and published in the journal BioScience, which found that one of the most profound impacts of urbanization is the "reconfiguration of surface hydrology."

Lead author John Roach, now with Simbiotic Software in Missoula, Mont., ASU professors Nancy Grimm and J. Ramon Arrowsmith and other former graduate students mapped water resources and connectivity and tracked land-use change in the Indian Bend Watershed (IBW). The researchers, associated with the Central Arizona-Phoenix Long Term Ecological Research project (CAP-LTER) and the Integrative Graduate Education and Research Training (IGERT) in Urban Ecology funded by the National Science Foundation, found that construction of artificial lakes and canal systems along with extensive groundwater pumping have had "unintended impacts on nutrient cycling."

"As Phoenix grew from a small settlement to the large urban center it is today, it built an extensive canal network to bring water from the Salt, Verde, and Colorado rivers to agricultural fields and city taps," says Roach. "While these canals enabled farmers to grow crops in the desert, they also cut across stream channels, disrupting the flow of water and sediments from tributary networks to the main channel. In pristine streams, sandbars and other patches created where these sediments collect are often ideal places for nutrient cycling. By starving streams of their historic supply of this material, canals accidentally alter the way nutrients are cycled in stream ecosystems."

Humans have altered water systems in the Phoenix area as far back as 300 B.C. The Hohokam people constructed an extensive series of canals for irrigation in the region (until 1450 A.D.) A new group of settlers arrived in the 1860s and immediately began building "ditches" or simple irrigation canals. Construction continued through the 1900s as dams were built to harness the Salt and Verde rivers and the canal system was expanded to bring more land under cultivation. As the area became more urban, flood control became more important, necessitating construction of the Indian Bend Wash greenbelt, one of the first non-structural flood management structures in the United States. These activities altered surface water availability, dramatically increasing the timing and spatial distribution of stream flow.

"Prior to these alterations, channel systems like those of Indian Bend Wash were ephemeral, storm precipitation-driven systems with only a limited connection to the groundwater (via loss from the channel bed)," notes Ramon Arrowsmith, professor with School of Earth and Space Exploration in ASU's College of Liberal Arts and Sciences. "Now, the surface and subsurface hydrologic network is short-circuited with water entering the channel from well and canal sources, and water leaving by important evaporation, seepage, and canal redirection."

The authors emphasize how modern urban water systems shatter any limitations imposed by the topographic contours of a region. The Central Arizona Project cuts a blue swatch across the Sonoran Desert and subdivides watersheds, to deliver a reported 1.7 Ãƒâ€” 109 m³ per year (or 1.5 million acre-feet) of surface water to the area. In addition, the pumping of ground water has dropped the water table 90 meters and connected surface and subsurface flows, "not only increasing the spatial and temporal availability of water, but having the unintended effect of increasing the flux of NO₃ through urban waterways by returning nitrogen leached from historic fertilizer applications to surface flows."

One concern is the potential impact on riparian species, the "integrity of native ecosystems and the continued delivery of goods and services from these ecosystems."

Streams in deserts are often overlooked in their importance because of their ephemeral nature; however, streams in general have been shown to be critical to the removal of excess nitrogen from agricultural fields and wastewater runoff from urban areas. Denitrification, a bacterially-mediated process, converts nitrate to nitrogen gas, which then is released harmlessly to the atmosphere. High nitrogen loads from urban areas can overwhelm streams' capacity to remove nitrates and the resulting pollution of downstream rivers has been linked to the proliferation of coastal dead zones. (Read more about streams and coastal zones.)

"We were surprised by how frequently the concentration of nitrate in surface waters was determined by the turning of a tap," Roach notes. "Because the groundwater below the greater Phoenix ecosystem contains a lot of nitrate, when groundwater wells are tuned on, the concentration of nitrate in the canals and streams receiving this water goes up. This nitrogen, in turn, can act as fertilizer, stimulating unwanted growth and producing changes in what the stream looks like that are independent of the decision to deliver more water to city lawns."

The present study underscores the importance of understanding the structure and function of natural streams and arid ecosystems and how they are impacted by human-altered systems, water distribution and design. The authors point out that the unintended consequences "must be carefully evaluated—especially in arid and semiarid cities—if managers are to have any hope of mitigating them."

Grimm, a professor in the School of Life Sciences and member of the Global Institute of Sustainability at ASU, sums their study up: "Our findings contribute to answering the more general question of how fundamental ecosystem services—those processes of ecosystems that provide a natural resource or regulate properties of the resource, for example—change when people make large alterations to streams during the course of urban development. Perhaps our case study will help define how to best design such ecosystems to meet the need to provide multiple services—in this case, protection from flooding, recreation, and regulation of nutrient concentrations reaching downstream systems."

This article first appeared in SOLS News.

Read more about urban ecosystems in "Taking measure of the megacity."

For more information contact, Nancy Grimm, nbgrimm@asu.edu or Ramon Arrowsmith, ramon.arrowsmith@asu.edu

Genes and nutrition influence caste in unusual species of harvester ant

ovprea — Mon, 25 Aug 2008 16:55:29 -0600

A minor worker of P. badius carrying an exceptionally large seed (two times her own body mass) back to the nest. (photograph by Chris R. Smith)

Is nature or nurture more important in determining an ant's status in the colony? That is the question researchers posed in a new study of the Florida harvester ant, Pogonomyrmex badius, a resilient creature found in many parts of the southeastern United States. The answer? Both nature (i.e. the ant's genetic makeup) and nurture (what it eats, for example) play a role in determining its fate.

The research team included scientists from the University of Illinois, the University of Arizona, Linfield College and Arizona State University. The findings were published online on August 14 by American Naturalist.

In the hierarchy of an ant colony, status is everything. If you are a "gyne" and thus destined to become a queen, you can expect the very best accommodations and generous portions at mealtimes. If you are a worker, you must be ready to sacrifice your health, welfare and reproductive capacity for the betterment of the colony.

The researchers were drawn to P. badius because its social structure is more complex than most. Its caste system includes two categories of workers: majors and minors. Major workers are nearly four times heavier than minors, but the minors outnumber them by 20:1. Gynes (pronounced "JINES") are about eight times heavier than minors.

The researchers wanted to know whether the ant's genetic endowment dictated its caste and size or whether nutrition also played a role.

"Basically what we found is that things are more complicated than previously thought," said Christopher R. Smith, a former graduate student in the School of Integrative Biology at Illinois and corresponding author on the study. "Our study shows that there is a large genetic component to caste determination, but that there is also a very strong environmental component."

The researchers found that the genetic makeup of the colonies they studied was quite diverse. The average P. badius queen had mated with at least 20 males (the norm for ants is one to five). The genetic analysis also suggested that the offspring of most males could develop into any caste, but that some male lineages (patrilines) were more likely to become gynes while others were more likely to become major or minor workers.

A recent study of honeybees found that colonies with a lot of genetic diversity were better at nest building and finding and storing food than their less diverse counterparts.

While historically, it has been assumed that castes are environmentally determined, recent studies on Pogonomyrmex harvester ants have found colonies in which becoming a worker or gyne is determined exclusively by genetic differences. This constrains the colony's ability to adaptively adjust to environmental realities. For example, colonies that have few workers and yet produce many larvae that are destined to become gynes fail to grow to maturity because they lack the resources to feed the voracious gynes. On the other hand, colonies that can respond to environmental factors and alter the ratio of the castes they produce are often more successful in a changing environment. They can produce more workers when resources are scarce and more gynes when food is plentiful.

"Flexibility in caste determination is essential as it allows the colony to respond to changes in need or environmental fluctuations," said principal investigator Andrew Suarez, an Illinois professor of animal biology and of entomology and an affiliate of the Institute for Genomic Biology.

The three female castes of the Florida harvester ant, Pogonomyrmex badius. Clockwise from the top: new queen, major worker, minor worker. (photograph by Adrian A. Smith)

In the new study, the researchers analyzed what the P. badius ants were eating. Using stable isotope analysis, which looks for different versions of elements such as nitrogen and carbon in the diet, the researchers could tell whether individual ants were eating higher or lower on the food chain. Those at the top would have a more carnivorous diet, with a higher nitrogen content in their foods. They would also ingest more of a specific isotope of nitrogen in their foods than those eating seeds or plants.

The analysis showed that gynes were at the top of the dietary food chain and had the highest proportion of nitrogen in their diets. The minor workers had the lowest nitrogen content and were eating primarily from plant rather than animal sources. The majors were getting a better diet than the minors, but were not eating as well as the gynes.

"Differences in the nutrition that an individual assimilated during larval growth are strong predictors of caste," the authors wrote.
The researchers also found that genetic differences predict size in major workers and gynes, but not minor workers. Minor workers increase in size only as the colony grows, probably because larger colonies have more resources available to them.

The exact mechanisms by which genetics or diet influence caste are not yet known, Smith said, but in P. badius both play an important role. There may be a hormonal response, for example, that is driven in part by genetics and in part by nutrition that determines the trajectory of an individual ant's development, he said. Smith, currently a post-doctoral fellow at Arizona State University, continues to investigate how genetic differences interact with variation in diet to generate so much diversity in the form and function of all ants.

The fact that nutrition can alter the genetic destiny of some individuals in the colony probably allows the colony to adjust the ratio of workers to gynes to survive in tough times.

"But there are still Ã¢â‚¬Ëœhaves' and Ã¢â‚¬Ëœhave nots' in the colony: those genetic variants who have a reproductive advantage and those that don't," Smith said. "The ant colony and human society have striking parallels."

Smith quotes Marx and Engels, who theorized in their manifesto: "The history of all past society has consisted in the development of class antagonismsÃ¢â‚¬Â¦the exploitation of one part of society by the other."

This article first appeared in SOLS News. For more information contact Diana Yates, University of Illinois, 217.333.5802, diya@illinois.edu or Margaret Coulombe, ASU School of Life Sciences, 480.727.8934, margaret.coulombe@asu.edu

DNA detection could cut airport wait times

ovprea — Mon, 14 Apr 2008 15:24:15 -0600

(Read the full text in SOLS News)

Streams play key role in protecting coastal zones

ovprea — Mon, 17 Mar 2008 17:59:01 -0600

by Margaret Coulombe

Stream

The plight of the world's oceans is dire, according to recent studies, through insults from human activities that are depopulating and damaging reefs, altering coastlines, and creating pollutants, such as nitrogen runoff from terrestrial watersheds.

A study by 31 aquatic biologists involving 72 stream sites in the United States and Puerto Rico has found that one critical buffer to excess nitrogen runoff from agricultural and urban areas turns out to be small streams and rivers. The findings are published March 12 in the journal Nature.

"We found that nitrate was filtered from stream water by tiny organisms such as algae, fungi and bacteria," says Patrick Mulholland, lead author of the study and a member of Oak Ridge National Laboratory's Environmental Sciences Division, with a joint appointment at the University of Tennessee. "Further, our model showed that the entire stream network is important in removing pollution from stream water."

The study used a rare nitrogen isotope to examine the effects of nitrogen loading in streams. The researchers analyzed its removal relative to the amount of nitrogen present in the stream overall. The results showed that much of the nitrogen was removed by bacteria in a process called denitrification, which releases harmless nitrogen gas into the atmosphere. However, the study also demonstrated that as nitrate loads increase, the efficiency of removal was reduced.

"Our study shows that nitrogen loading compromises the ability of streams to retain or transform nitrate, a major pollutant that has been associated with lake and stream eutrophication, groundwater pollution, and coastal dead zones," says Nancy Grimm, an ecologist at Arizona State University who has been involved with the project since the 1980s.

Presently it's believed that small streams and rivers remove three-quarters of the excess nitrogen contamination before it reaches the oceans by acting as "sinks." However, the researchers' findings suggest that as land use changes, and shifts to increasing nitrogen loads occur, that this buffering capacity could be overwhelmed. Nitrogen pollution could generate algal blooms, oxygen depletion (dead zones) and death to coral, fish and shellfish in coastal zones.

Grimm believes that the long-term, collaborative nature of the project supporting this study, which has incorporated two separate experiments each conducted in a range of ecosystems, was key to "advancing understanding of stream nitrogen dynamics far beyond what could be accomplished with a single-investigator grant focused on one region."

As a professor in ASU's School of Life Sciences, Grimm is no stranger to long-term collaborative efforts. For the last 10 years she has led the Central Arizona-Phoenix Long-term Ecological Research (CAP-LTER) project centered on the analysis of urban-semi-arid ecosystem relationships. The co-director of CAP-LTER is anthropologist Charles Redman, director of ASU's School of Sustainability.

With her collaborators, Grimm has established a conceptual basis for including human choice and action in theory of urban ecosystem dynamics. Grimm and her counterparts' empirical work on biogeochemistry, species distribution and abundance, and designed aquatic ecosystems in cities have revealed that many ecological features are best explained by combinations of social and biophysical drivers. Grimm was also the first to describe nitrogen cycling in desert streams, work that led directly to the long-term collaboration and the experiments described in the Nature article.

The findings published in Nature underscore the critical interplay that exists between human action and ecosystems dynamics and capacity, and emphasizes "the management imperative of controlling nitrogen loading to streams and protecting or restoring stream ecosystems to maintain or enhance their nitrogen removal functions."

Along with Mulholland and Grimm, other collaborators on this study include scientists from the Woods Hole Marine Biological Laboratories, University of Georgia, Athens; Eco-Metrics; University of Wyoming, Laramie; Michigan State University; University of Notre Dame; Oregon State University; University of New Mexico; Kansas State University; Institute of Ecosystem Studies; U.S. Forest Service; University of New Hampshire; Virginia Tech; and Ball State University.

This story first appeared in SOLS News. For more information, contact Nancy Grimm, nbgrimm@asu.edu, 480.965.4735. For media inquiries contact Margaret Coulombe, Margaret.Coulombe@asu.edu, 480.727.8934.

Oceanic maps show human impacts gone global

ovprea — Thu, 21 Feb 2008 15:11:12 -0700

Read the full text at SOLS News:
http://sols.asu.edu/sols_news/08_news_08.php

Taking measure of the megacity

ovprea — Mon, 11 Feb 2008 16:15:50 -0700

by Margaret Coulombe

If you are reading this, chances are that you live in a city—one, perhaps, on its way to becoming a megacity with a population that exceeds 10 million or more. If not, you and most of the world's population soon will be, according to global population demographics projections.

What shape could these future cities take and how will their populations meet environmental and resource challenges? An article, "Global Change and the Ecology of Cities," published in the journal Science on Feb. 8, 2008, by Arizona State University ecologist Nancy Grimm and her colleagues, addresses these questions.

"When we think of global change, images of melting ice caps and pasture replacing tropic rainforest come to mind," Grimm says. "What drives these changes? In fact, much of the current environmental impact originates in cities, and with demographic transition to city life the urban footprint is likely to continue to grow."

Grimm's co-authors include ecologists John Briggs, Stan Faeth, and Jianguo (Jingle) Wu of ASU's School of Life Sciences; archaeologist Charles Redman, director of the ASU School of Sustainability; as well as researchers, Nancy Golubiewski from New Zealand Centre for Ecological Economics and Xuemei Bai of CSIRO Sustainable Ecosystems in Australia.

Urban challenges face communities worldwide, with solutions lagging behind. Grimm and her colleagues promote a global perspective of urban development. Their analyses capture some of the commonalities that will face future city planners and societies, viewing cities as both drivers of and responders to environmental change. The authors chart the socio-ecological challenges and changes ahead for all cities, but particularly those in rapidly developing regions, like China and India.

These changes range from land use and cover, urban waste discharge and urban heat island effects to global climate change, hydrosystems, biodiversity and biogeochemical cycles. In all, the authors demonstrate that cities are substantive ecosystems in their own right, replete with complex human-environmental interactions and far-reaching impacts.

"Cities, and the people in them, will ultimately determine the global biodiversity and ecosystem functioning," says Wu. "Sustainable urbanization is an unavoidable path to regional and global sustainability."

Cities as ecosystems
For a decade, Grimm, Redman and more than a dozen co-principal investigators have pioneered urban studies in one of the first long-term ecological research (LTER) projects designed about urban environments. One of two urban long-term projects funded by the National Science Foundation (NSF)—the other is the Baltimore Ecosystem Study in Maryland—CAP LTER researchers have examined the living and non-living components of a city with participation from city planners, engineers, sociologists and other scientists, revealing the dynamic nature of this "ascendant ecosystem."

"Urban areas are hot spots that drive environmental change," says John Briggs. "They are complex, adaptive socioecological systems, centers of production and consumption, in which the delivery of the ecosystems services link society and ecosystems at multiple levels."

Phoenix's rapid growth provides a platform for CAP LTER researchers, as an evolving "before" and "after" laboratory. Phoenix is the fifth largest city in the U.S., with a metro area population or more than 4 million. Phoenix's growth is emblematic of the U.S. West in general, which is expected to experience the largest percentages of population increases in the next 20 years.

"Phoenix, and cities in general, are microcosms for the kinds of changes that are happening globally," notes Grimm. "In biogeochemical cycles, for example, they show symptoms of the imbalances in nitrogen, carbon dioxide, ozone and other chemicals that they help to create globally."

Life on the edge
Cities literally are proving to be a hotbed for environmental research. Studies by urban ecologists reveal that city centers are physically hotter. Known as the heat island effect, urban and suburban temperatures are "2 to 10 degrees F (1 to 6 degrees C) hotter than nearby rural areas," according to the Environmental Protection Agency. This rise in temperatures translates into "increases in peak energy demand, air conditioning costs, air pollution levels and heat-related illness and mortality."

Just a one-degree rise in temperature can bump up residential water use 290 gallons per month on average for a single-family unit. However, knowledge about heat island effects also has meant innovation and the rise of new and greener technologies, such as roofing materials with a high solar reflectance and recycled rubber/asphalt composites to pave roadways.

But not all the challenges that occur in the city stay in the city. Grimm says rural landscapes at a city's edge show changes in soils, built structures, human settlements, the diversity of plant and animal species and further impacts on fringe ecosystems. The authors invoke future thinking about cities and their effects as expressed by urban planner and policy expert Robert Lang, of Virginia Polytechnic Institute and State University. Lang believes that a city's "footprint" has ballooned so that "cities are no longer independent, but represent a limited number of dominant megapolitan regions across the globe, with coalitions of urban centers built up in the intervening areas."

"What we see is that landscapes, virtually anywhere in the world, will experience the impact of the growth and operation of nearby and long distance cities," Redman says. "We need to understand the complexity of impacts that rapid global urbanization has both within urban boundaries and across landscapes at increasing distance."

How can so many environmental challenges and changes be considered in any unified way? One recent approach has been to view urban systems as organic units: organisms that take up resources and produce wastes. Though controversial, such an integrated perspective can be useful for interpreting such things as biogeochemical cycles in cities and to analyze their regional or global effects. For example, cities are point sources for carbon dioxide and other greenhouse gases, and anthropogenic nutrient deposition. Fall out from cities can come in the form of urban aerosols, including atmospheric nitrogen, such as that wafted from fast-food joints or manicured lawns.

Studies by Sharon Hall, an ecologist with ASU's College of Liberal Arts and Sciences, and Grimm find that fertilized and irrigated lawns release more nitrous oxide, a potent greenhouse gas, than the native desert soils that preceded them. Also, lawns support a more sustained, year-round production of nitrogen oxide than desert soils, which contributes to tropospheric ozone production and regional increases in photochemical smog.

"Global emissions of nitrous oxide (N₂O) and nitric oxide (NO) have increased dramatically during the last century, primarily due to human activity associated with agriculture and fossil fuel combustion," notes Hall. "We are just now discovering how urban centers figure into this equation, and how cities such as Phoenix impact surrounding landscapes, as well as contribute to larger regional or global climate."

Studies over the last 10 years by Wu and his students using geospatial analysis and computer modeling have shown that the Phoenix urban landscape has become geometrically more complex, but ecologically more fragmented. Also, urbanization-induced increases in temperature, CO₂, and nitrogen deposition will significantly affect the productivity, carbon and nitrogen cycling, and a suite of biogeochemical processes of the native ecosystems, resulting in altered ecosystem functioning and services.

Selection and the city
Biodiversity studies in cities are equally revealing. Urban environments alter species compositions, biomass, distributions and ecosystem function. Studies by CAP-LTER and other groups show that plant types and habitat patches are, somewhat counter intuitively, increased by human activity relative to wild areas and involve a socio-economic component. Wealthier neighborhoods plant more exotics and show increases in yard-to-yard heterogeneity.

Co-author, Faeth, has found that numbers of birds and arthropods like grass hoppers, jump within city boundaries—though at the cost of a diversity of types. In addition, urban-dwelling species often flourish at the expense of indigenous species, the long-term effects of which may be reflected in altered life-history traits and, potentially, evolution. Thus, Faeth notes, cities are ecological and evolutionary arenas that create novel environments, with selective pressures that change flora and fauna, including human "fauna," and that these will become more prevalent worldwide. The article points out that, worldwide, cities alter the behaviors, physiologies, disease patterns, population densities, morphologies and genetics of city-dwelling organisms.

"Cities create novel biological communities and these communities, no matter how Ã¢â‚¬Ëœunnatural' they are, are the ones that most humans know, and in the future, will experience," Faeth says.

"Knowing how cities function, how the Ã¢â‚¬Ëœecosystem services' they provide can be enhanced through planning and urban design, gives us a chance to improve the quality of life and the environment for animal, plant and human inhabitants of cities," Grimm says. "Although every city and its surrounding environment are different, ecological studies of those differences, and participation of ecologists in decision making, can create solutions that apply across many situations."

The NSF became an active partner in long-term urban study in 1997 with the launch of the central Arizona and Baltimore LTER programs. Since then, NSF has expanded support for urban systems research through a wide range of directorates, reflecting the complex questions at hand, encompassing biological sciences, geosciences, social, behavioral, and economic studies, and environmental research and education programs.

"Agglomerations of people in cities increasingly dominate environmental change globally, but are clearly understudied from an ecological standpoint," notes Henry Gholz, of NSF's Division of Environmental Biology. "This hampers our abilities to scale ecological information and make informed predictions of, or policies regarding, future global ecological states."

Grim future?
Urban ecological study may be multi-faceted and complex, yet it offers pivotal insight in how to navigate a sustainable urban future. As soon-to-be dominant ecosystems, cities, harbor a wealth of ideas and creative accomplishments, as they have over centuries of urban living, Grimm and her colleagues say. Moreover, increasing public understanding that cities are more than miles of roadways, steel and glass means that urban ecosystems can be managed and that costs to citizens and environments can be understood and balanced.

"The relatively young and highly interdisciplinary field of urban ecology has demonstrated how well-designed cities can actually have less overall impact on the environment than equivalent dispersed rural populations," says Jonathan Fink, director of ASU's Global Institute of Sustainability. "The kind of counter-intuitive research results described in Grimm's paper show how an ecological perspective can help urban planners and engineers find ways for society to live more harmoniously with nature."

This article first appeared in SOLS News.

For more information, contact Nancy Grimm, 480.965.4735,
nbgrimm@asu.edu

Media contact: Margaret Coulombe, 480.727.8934, Margaret.Coulombe@asu.edu

Bacteria and sunlight make clean, green hydrogen

ovprea — Thu, 17 Jan 2008 14:34:59 -0700

by Skip Derra

If we wanted to create the ideal environmentally friendly energy source, it would be a fuel that is easy and economical to produce, and one that does not pollute our air when burned. That is exactly what researchers at Arizona State University intend to develop in a new program that uses bacteria and sunlight to generate hydrogen, a clean fuel that produces no greenhouse gases.

ASU's biohydrogen project aims to harness the energy in sunlight using microbial photosynthesis to produce hydrogen. A second part of this project is to convert waste materials from the initial process to produce even more hydrogen.

"Hydrogen is the purest fuel you can think of," says microbiologist Willem "Wim" Vermaas, a professor in ASU's School of Life Sciences and the lead investigator on the project. "It generates energy without releasing CO₂ into the atmosphere. It is the ultimate clean energy technology because you are splitting water to make the hydrogen. If you burn the hydrogen, you get water back. In essence, with our process you are converting solar energy into a clean fuel."

"Of course," he adds, "there are many challenges to making this process work efficiently."

Splitting water into its chemical constituents of hydrogen and oxygen can be done through other methods, like electrolysis. ASU's process is more elegant and does not require any energy other than sunlight. What makes the process work is finely tuned cyanobacteria to carry out the reaction.

Vermaas, a member of ASU's Center for Bioenergy and Photosynthesis, said that in the laboratory researchers have used a cyanobacterial system to generate a small amount of hydrogen using only solar energy. To optimize the system, the microorganism must be retooled to put most of the energy it gathers from sunlight into compounds useful for biohydrogen production.

The ASU researchers, who have years of experience working in this field, are using a cyanobacterium with a known genome and have developed it into a model organism for genetic and metabolic engineering studies. Using its natural photosynthesis machinery, "we are now starting to direct more of the photosynthetic activity into biofuel production, yielding organisms that convert substantially more of the harvested energy into biofuels," Vermaas says.

One of the main challenges for the researchers is finding an enzyme for hydrogen production, called hydrogenase, which can operate in the presence of oxygen. Hydrogenase enzymes are a key component to hydrogen production through the photosynthesis process. However, they currently are very sensitive to oxygen, a natural by-product of the splitting of water (H₂O).

"If you make photosynthetic hydrogen, you also make oxygen and you have a problem because oxygen inactivates the very enzyme that you want to have working," Vermaas explains.

One part of the project, headed up by Ferran Garcia-Pichel in the School of Life Sciences, is to find heartier forms of hydrogenase. Garcia-Pichel will be looking at systems that occur in nature.

"Preliminary data suggest that in a variety of natural habitats cyanobacteria can produce hydrogen, which means that unless there is some way the cells exclude oxygen from the process, their hydrogenase enzyme must be oxygen tolerant," Vermaas says.

"Boosting the oxygen tolerance of the hydrogenase is really a key to the overall system," he adds. With a robust hydrogenase enzyme, the next step is to incorporate their genes into the model cyanobacterial system. But the way they are incorporated and how the oxygen-tolerant hydrogenase is aligned with other enzymes in the cyanobacteria are critical to getting the system to work efficiently.

"We need to be able to effectively connect the hydrogenase to the photosynthetic reaction center complexes of the cyanobacteria," Vermaas says. "We can do that through metabolic engineering."

Each cyanobacterial cell is about 1.5 Ã‚Âµm in size, much smaller than what can be seen individually by the human eye. Bacteria's evolutionary drive is to multiply and in that process electrons and protons are used for the generation of energy and as building blocks for growth of the organism. In the modified cyanobacterial system, Vermaas wants to divert electrons from their normal pathways and push them into new pathways that result in hydrogen production.

"That can be done by more directly linking hydrogenase to where electrons come out of the photosynthetic pathway," he says. "So we are essentially hijacking the electrons to go to the hydrogenase where they, together with protons, form hydrogen."

The third part of the project is to create a microbial fuel cell technology that uses the left over cyanobacterial biomass generated in the hydrogen production process as the energy source for additional hydrogen production. Bruce Rittmann, director of the Center for Environmental Biotechnology at the Biodesign Institute at ASU is leading the effort in this area.

The researchers will develop the scientific and technological basis for microbial fuel cells that oxidize organic materials in biomass at their anodes, while generating hydrogen gas at their cathode. This work is expected to not only capture energy from cyanobacterial biomass, but it will lay the scientific groundwork for microbial conversion of energy from all kinds of biomass, including human and animal wastes, agricultural crops and residues, and ethanol. The process already has demonstrated that it can produce some energy, but Vermaas said there still is a long way to go to make it economical and efficient.

All of this work is based on many years of research that has been done at ASU, especially groundbreaking biochemical and molecular studies carried out by Tom and Ana Moore, Devens Gust, Jim Allen, Andrew Webber, Neal Woodbury and Anne Jones in the Center for Bioenergy and Photosynthesis. Jens Appel, a leading researcher on cyanobacterial hydrogenases, will join the team in January.

"We know the space we need to look in, and where to look in nature for solutions," Vermaas says. "We have the tools to do the work. We have good ideas on how to do metabolic engineering of the cyanobacteria. We just need to do more research to make it work effectively."

This article first appeared in SOLS News.

The project is one of the first to be funded by the ASU President's Intellectual Fusion fund. This endowed fund is supported by two recent gifts totaling $22 million, and is used to make seed investments in research areas that push the boundaries of traditional academic disciplines. Funding for the biohydrogen project ($2.5 million over five years) is being administered through the Global Istitute of Sustainability.

Read more about photosynthesis research at ASU in:
"Catching some rays: Harnessing the power of photosynthesis"
"Bacteria for biofuels"
"The power of green"