As Becker leaves the lecture hall to walk back to her office, she doesn't linger long in the afternoon sunshine. She's in a hurry to meet her students in the lab to help them troubleshoot a problematic protocol. Focused and directed, she makes each second of her day count.

Becker's focus keeps her grounded in a challenging career juggling act. A young assistant professor with a big lab, Becker also holds an appointment in University of Maryland Extension as an extension specialist in waste management. She focuses on education and outreach in the community — "anything with a treatment process," ranging from animal manure to stormwater treatment to bioremediation. Each year, she also leads sessions in a job-training program in Baltimore, preparing individuals for entry-level jobs in environmental fields.

In any given week, Becker's days range from academic work based in the lab to applied practical work with citizens of the state. She's involved in a lot of traditional agricultural engineering extension, teaching farmers how to manage manure so "nutrients don't go where they're not supposed to go." This ties her work directly to the challenging issue of slowing the flow of nutrients to the Chesapeake Bay.

She's also been involved in recent efforts to educate farmers about changes that affect implementation of federal air quality regulations. A national study to monitor emissions from animal feeding operations seeks to set size limits for animal operations defined by their emission output — for example, a poultry operation with over 75,000 chickens might be determined to emit too much ammonia, explains Becker. Animal operations that exceed size-based thresholds will be considered emitters and subject to potential lawsuits under a violation of the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA). Becker works to keep citizens aware of what these changes could mean for their businesses.

"Finding a balance between my research and extension programs has been huge," says Becker. "Sometimes I do feel spread thin. But it is very rewarding to help farmers do their job better and to help people get jobs. That is very inspiring to me," she says.

Becker's balancing act seems to be working. In 2002, she received a prestigious Faculty Early Career Development Award (CAREER) from the National Science Foundation (NSF). NSF subsequently selected her from among CAREER grant awardees to receive a Presidential Early Career Award for Scientists and Engineers. This award, established by President Clinton in 1996, is considered to be "the highest honor bestowed by the United States government on scientists and engineers beginning their independent careers."

Nature may not always provide a convenient means of cleaning up human messes.

After a quick stop by her office, Becker heads down to the lab to work with her students on their troublesome protocol. She grabs a can of seltzer on the way down, but doesn't break for lunch. Her post-doc, Hong Yin, and student, Yen-jung Lai, are working with growth media used to maintain a large volume of bacterial culture. The media shows signs of contamination. They've recently seen white filamentous organisms growing in it that shouldn't be there. With Becker supervising, they plan to work through the preparation steps to see if together they can identify the problem.

As they prepare their laboratory equipment, Becker shifts mental gears and enters her practical problem-solving mode. She knows that her ability to prove her theory about how bacteria like D. ethenogenes compete in the environment depends on the success of these time-consuming experiments, which require meticulous attention to detail.

But Becker never loses sight of the bigger context for her research. She's propelled by the idea that the better we can understand how these PCE and TCE-breathing bacteria do what they do, the better we will become at harnessing their power to clean up contaminated sites.

She recognizes that her work on how pollutant-busting bacteria function in their natural environment touches on a question that is even bigger still. How did these bacteria "learn" to break down compounds that they've never encountered before?

The environment has only seen compounds like PCE and TCE for a short time, since after World War II, explains Becker. But bacteria that can break down these compounds did not appear out of nowhere. "Dehalococcoides did not magically evolve these enzymes overnight," agrees Rekha Seshadri, a microbiologist at the Institute for Genomic Research in Rockville, Maryland.

For centuries, bacteria have had natural compounds similar to PCE to work on, explains Becker. However, their concentrations are much lower than can be found at contaminated sites. Some insects, for example, produce chlorinated compounds to protect themselves in what could be considered chemical warfare, and volcanoes may also produce related compounds, Becker says.

Bacteria that break down these natural PCE-like compounds likely acquired mutations that allowed them to respire the man-made ones. Then as pollution in the environment became more widespread, bacteria that could live off these new toxins thrived, Seshadri says, thus selecting for bigger and bigger populations of these bacteria.

The microbial goings-on beneath the former Kings Cleaners remain a mystery.

Seshadri spearheaded the efforts of a group of scientists to sequence the genome of D. ethenogenes, which was published in Science last year. The bug's genetic code revealed its complete dedication to the process of breaking down compounds like PCE. Its genes contained very little extraneous information — only the bare bones necessary to encode the enzymes directly involved in the breakdown process.

The genome sequence also provided hints that D. ethenogenes is evolving rapidly and customizing its physiology to meet the demands of the environment, explains Seshadri. The group found that structures called "integrated islands" make up a surprisingly large percentage of the bug's total genetic material. These "islands" are like footprints of a recent genetic exchange. They reveal areas where D. ethenogenes may have swapped material with another species of bacteria.

Many bacteria like D. ethenogenes appear to evolve rapidly to meet the demands of new and increasingly obnoxious chemicals in the environment — acting as invisible checks and balances on the forces pulling the Earth away from equilibrium. Nature may not always provide a convenient means of cleaning up human messes, says Seshadri. And in the meantime, such pollutants continue to take their toll on human life and health.

Change comes to the human landscape, as the crumbling shell of an abandoned bowling alley makes way for a new warehouse. State officials are certifying that the soil is safe, but not the groundwater below. No wells will be allowed on this location. The subterranean aquifer must remain undisturbed. Photograph by Erica Goldman.

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