Dianne Newman is exploring the deep connection between bacteria and rocks -- specifically, the possibility that some varieties of ancient microorganisms gave rise over millennia to vast mineral deposits. She’s intrigued in particular by enormous banded iron formations found on every continent that contain rich evidence of the important role of bacteria.
Newman and her colleagues examine this ore in big and small chunks, and from a biochemical perspective. Buried inside lie fossils of microorganisms and their processes, and it’s by the “careful interpretation of the rock record that we make progress,” says Newman. 3.4 billion-year-old rock chunks called stromatolites contain fossil shapes that look like “microbial mats rolled up,” and filaments resembling the structures some bacteria use for photosynthesis, the process by which modern-day plants split water using sunlight to produce their food. There are also molecule-scale fossils of cyanobacteria (blue green algae), a photosynthetic microorganism, preserved in 2.5 billion year old rock. In the days before atmospheric oxygen became abundant on Earth, could primitive bacteria have used a photosynthetic process based on other elements, like iron, and yielded enormous mineral deposits over time?
To learn what microbial community might have produced stromatolites and other such rocks, Newman headed down to a salt marsh in Woods Hole, to “dig in the sand and see microbial mats with various layers of bacteria” -- cyanobacteria on the top, green and purple beneath and on the bottom, sulfate-reducing bacteria. While scientists have demonstrated that the metabolism of oxygen-producing cyanobacteria stimulates the formation of calcium carbonate minerals, it has been uncertain whether the other bacteria, which don’t produce oxygen, can do the trick of creating such minerals.
Newman’s students found samples of such bacteria near a rusty staircase in Woods Hole and isolated from them a gene required for iron oxidation, part of the process of turning the element of iron into the kind of minerals found in banded iron deposits. Students cultured these bacteria, and watched mineral formations emerge in response to light. Newman ran the numbers to figure out if ancient earth oceans containing such bacteria might have produced the kind of minerals seen in banded iron formations.
The result, she reports, is “encouraging” but not yet conclusive. Ambiguity remains, because non-biological processes might also have produced these formations. For her though, “this question is profound, fascinating and hard to answer. The evolution, when, and how, of different types of photosynthesis remains a mystery, awaiting the next generation of Earth scientists and molecular biologists.”
ABOUT THE SPEAKER:
Dianne Newman explores how microbes affect the structure of the rocks in which they grow, specifically how they use minerals like arsenic and iron in their metabolism. It's an area of research that is yielding new insight into the earliest forms of life while offering a framework for studying the phenomenon of bacterial biofilms.
She studies how anaerobic bacteria survived millions of years ago, before the atmosphere contained oxygen. These bacteria, in essence, "breathed" iron, and Newman focuses on how they used it in the electron transfer process that was fundamental for their metabolism.
Newman received a B.A in German studies from Stanford University, and a Ph.D., in Civil and Environmental Engineering, from MIT. She has been a David and Lucile Packard Fellow in Science and Engineering, and won the Young Investigator Award from the Office of Naval Research.
From Rocks to Genes and Back: Stories about the Evolution of Photosynthesis
Related Media and Events
NREL-MIT study shows an 80 percent renewable energy standard cuts water use in half.
In his first State of the Union address, President Barack Obama set a goal for 80 percent of America's electricity to come from clean energy. Last week, the release of the Renewable Electricity Future study by the U.S. National Renewable Energy Laboratory (NREL) confirms that reaching this goal by 2050 is very possible. But what impact would clean energy have on another key ingredient to daily life: clean water? Researchers at MIT helped answer that question in NREL's report.
The MIT research—Modeling Water Withdrawal and Consumption for Electricity Generation in the United States—is a compilation of the water segment of the Renewable Electricity Future study. In it, the researchers find that as solar panels, wind turbines and other sources of non-thermal renewable energy replace coal, gas and similar thermal powerplants, the use of water to cool those powerplants will decrease by about half.
"The most important use of water for electricity production is for cooling," says Adam Schlosser, an author of the study and the assistant director for science research at MIT's Joint Program on the Science and Policy of Global Change. "The benefit of renewables like wind or solar is that you don't need to boil water for steam to spin the turbines, and then you don't need water to cool the steam. That cooling process is removed, saving a lot of water."
This is good news for water-stressed regions, including much of the western United States, as production of electrical power results in one of the largest uses of water in the nation. A 2005 report by the U.S. Geological Survey found that about 201,000 million gallons of water each day were used to produce electricity, with much of this water going toward keeping powerplants cool.
While most Americans will use less water when powering their homes with renewable energy, the MIT researchers did find that areas that switch to thermal renewable technologies might end up using more water. Biomass energy, being produced mostly in the northwestern United States, is one strong example, the study finds.
"Biomass is obviously contributing to the carbon aspect of the overall problem," Schlosser says, "But it's actually exacerbating an already water-stressed situation because you not only need water to grow it, you also need water to cool the thermal electricity generation process."
Schlosser compares this to concentrated solar technology being used in the southwest, which typically relies on a dry cooling system where fans are used instead of water.
"Solar technology really benefits the southwest because it uses a resource that's so plentiful in that region—the sun—and doesn't use a resource that there is very little of—water," Schlosser says.
But Schlosser explains that the dry cooling technology—while an obvious choice for the drought-stricken southwestern United States because it uses 90 percent less water—is less efficient and more expensive because the electric plant would need to use electricity to run large fans that force air through the heat-exchange process. This explains why areas where water scarcity is more subtle would choose to stick to water cooling technologies in thermal electricity generation.
Along with using less water, the Renewable Electricity Future study finds that greenhouse gas emissions would be reduced by about 80 percent, potentially offering significant public health benefits. The National Research Council estimated that in 2005, air pollution emissions from coal powerplants cost $32 per megawatt of energy in public health damages, the report notes, suggesting that the health cost benefits could counterbalance the costs to build clean energy infrastructure.
RELATED - Union of Concerned Scientists Webinar
Three Questions with Research Scientist Sebastian Rausch
Alli Gold Roberts
MIT Joint Program on the Science and Policy of Global Change
Population growth and increasing social pressures on global water resources have required communities around the globe to focus on the future of water availability. Global climate change is expected to further exacerbate the demands on water-stressed regions. In an effort to assess future water demands and the impacts of climate change, MIT researchers have used a new modeling tool to calculate the ability of global water resources to meet water needs through 2050.
The researchers expect 5 billion (52 percent) of the world’s projected 9.7 billion people to live in water-stressed areas by 2050. They also expect about 1 billion more people to be living in areas where water demand exceeds surface-water supply. A large portion of these regions already face water stress—most notably India, Northern Africa and the Middle East.
The study applies the MIT Integrated Global System Model Water Resource System (IGSM-WRS), a modeling tool with the ability to assess both changing climate and socioeconomics—allowing the researchers to isolate these two influencers. In studying the socioeconomic changes, they find population and economic growth are responsible for most of the increased water stress. Such changes will lead to an additional 1.8 billion people globally living in water-stressed regions.
“Our research highlights the substantial influence of socioeconomic growth on global water resources, potentially worsened by climate change,” says Adam Schlosser, the assistant director of science research at the Joint Program on Global Change and lead author of the study. “Developing nations are expected to face the brunt of these rising water demands, with 80 percent of this additional 1.8 billion living in developing countries.”
Looking at the influence of climate change alone, the researchers find a different result. Climate change will have a greater impact on water resources in developed countries. This is because, for instance, changes in precipitation patterns would limit water supplies needed for irrigation.
When researchers combine the climate and socioeconomic scenarios, a more complicated picture of future water resources emerges. For example, in India, researchers expect to see significant increases in precipitation, contributing to improved water supplies. However, India’s projected population growth and economic development will cause water demands to outstrip surface-water supply.
“There is a growing need for modeling and analysis like this, which takes a comprehensive approach by studying the influence of both climatic and socioeconomic changes and their effects on both supply and demand projections,” says Schlosser. “Our results underscore this need.”
The MIT team plans to continue this work by focusing on specific regions and conducting more detailed analysis of future climate changes and risks to water systems. They plan to refine and add to the model as they research other regions of the globe.