Perspectives Online

College ProfileSoil microbiologist Dr. Alexandria Graves zeroes in on the sources of ecosystem contamination to both clean up and prevent pollution. By Dee Shore


Dr. Alexandria Graves
Photo by Marc Hall

Every year from sixth grade until 12th, Alexandria Graves visited N.C. State University’s campus for cheerleading camp. But never during all that time did she imagine that one day she would be a faculty member here. And it certainly never occurred to her that her work would involve studying fecal contamination.

But today, as an assistant professor in the College of Agriculture and Life Sciences’ Department of Soil Science, Dr. Graves studies the causes of contamination in water bodies, soils and food.

It’s work that has important implications for public policy, public health and the economy, because knowing what’s causing pollution is key to stopping it.

And, as Graves points out, what’s causing pollution isn’t always readily apparent.

“When you have contamination, it’s easy to point the finger at agricultural or municipal sources or septic systems, but monitoring – just getting the numbers alone – doesn’t really tell you where it’s coming from,” she explains. “You really need to go beyond the numbers to source track if you are really going to identify the contributors.”

Source tracking is at the center of Graves’ work at N.C. State. It involves using antibiotic resistance and genetic markers to determine the source of bacteria in the environment. She and her students collect fecal samples from livestock and wildlife near contaminated sites and from human sources such as septic systems, as well. Then she builds a database — or “library” — against which unknown samples can be compared.

Pinpointing a contamination source opens the way for a cleanup that allows a formerly polluted area to be used for recreation, fishing and aquaculture. Not only that, it also gives policymakers the information they need to develop regulations that prevent future pollution.

A recently completed project in Sampson County, featured in the Summer 2009 issue of Perspectives, is exemplary of Graves’ source-tracking research. For that study, Graves’ graduate student Lloyd Liwimbi used antibiotic resistance genes recovered from E. coli to determine the sources of fecal pollution in a Sampson County creek that was in the heart of North Carolina’s swine production area. The study showed that swine production was actually not the major source of pollution. Rather, wildlife such as birds needed to be considered.

Now, Graves is wrapping up a project to determine sources of bacteria in Oyster Creek in Hyde County, and she has another experiment on Carteret County’s North River to evaluate water and sediment samples to determine sources of E. coli.

The river “is in a more urban area, so you get a mixed bag, essentially, of contributors,” Graves says. “Not only are wildlife associated, but you do see some pets as well as human sources contributing.”

When an area has many land uses, environmental pollution can be a controversial topic. Because of that, Graves takes extra steps to ensure that her work is accurate and can be double-checked.

“It’s not my objective to be involved in … legal situations. Rather, my objective is to provide information so policymakers and communities can be informed and decide what the best mitigation strategy should be,” she says.

“However, because it is still so controversial, our work has to be defendable. One has to make sure that they are maintaining the integrity of their work. For example, we use multiple methods. … (W)hen they tell you the same thing, you have some assurance of your results.”

While most of her work thus far has focused on fecal contamination in water bodies, Graves is also interested in using source tracking to identify the cause of foodborne illnesses. In 2006, researchers found that wild pigs were the likely cause of an E. coli outbreak on spinach that killed three and made hundreds in the United States and Canada sick. And birds were suspected in a more recent deadly case of Salmonella in peanut butter.

Graves sees the challenges related to fecal contamination, whether in North Carolina or beyond, to be sufficient to sustain her career well into the future.

“I think there will always be a need with regard to evaluating sources of fecal pollution, remediating these sources of pollution in the environment …, not only for water quality but also air and food protection, as well,” she says.

But Graves didn’t always see it that way. It was a circuitous and unpredicted path that led her to soil microbiology and her faculty position at N.C. State.


In her Williams Hall lab, Graves prepares a sample for testing as she tracks sources of water, soil and food pollutants.
Photo by Marc Hall
When she entered Winston-Salem State University in the 1990s as an undergraduate, the Yanceyville native figured she would one day work in some area of medicine. She started out as a medical technology major, then switched to physical therapy, then to biology and then microbiology.

That led to a fateful summer research training program at the National University of Singapore.

“I was in a microbiology lab, and we were working with soil samples. We were isolating bacteria from the soil because we wanted to get antifungal agents from those bacteria for a long-term goal of developing new antifungal drugs, especially for the immuno-compromised patient,” Graves says. “And so that was my first introduction to more of the agriculture side of microbiology, but yet there’s still a connection with public health.”

Following that experience, Graves set her sights on earning a Ph.D. in microbiology, landing a spot in the master’s program in the Department of Crop and Soil Environmental Sciences at Virginia Tech and ultimately getting her doctorate in 2003. She then conducted post-doctoral research at Texas A&M before returning to her home state to join NCSU’s faculty.

Graves is now pursuing tenure, juggling teaching of two soil microbiology courses, advising students, conducting research and getting that research published. She’s also a single mother to a 7-year-old daughter, Chloe.

“It’s a lot, and I’m sweating buckets trying to get things accomplished and things out the door,” she says.

‘Soil microbiology is so interconnected to many other disciplines, and it impacts everything we do — from the air we breathe to the food we eat and the water we drink.’
When all’s said and done, Graves hopes to look back and see that her work has added up to a “better understanding of some of these fecal bacteria and an overall understanding of various contributors.

“I think ultimately if we get a better understanding of how these organisms are moving through our environment and how they are impacting our ecosystem — and the ecosystem impacting these organisms — we can get a better handle on how to reduce or eliminate some of these bugs in the environment.”

Once the tenure process is behind her, Graves hopes to become more active in introducing people to the soil microbiology. She sees herself interacting with elementary and high school students and getting involved in community projects that let young people know of the possible careers in agricultural science and soil microbiology — careers she didn’t have an inkling of back when she was involved in those cheerleading camps.

Graves also hopes to continue teaching. Many of her students take soil microbiology to fulfill a requirement rather than out of interest, and so she loves “seeing the light bulb go on. Typically by the end of the semester, they have such a greater appreciation for soil microbiology.

“As I tell them, soil microbiology is so interconnected to many other disciplines, and it impacts everything we do — from the air we breathe to the food we eat and the water we drink. I never would have imagined it.”