Odd Couple Could Clean Water

Researcher Looks at Bacteria, Manganese to Trap Harmful Metals

March 24, 2009

By Russ L. Hudson

It sounds counterintuitive, but a mix of the metal manganese and bacteria could be a recipe for cleansing contaminated soil and water deep in underground aquifers with a cheaper, less labor-intensive method of bioremediation.

Researchers theorize that adding manganese and bacterial microbes that oxidize the metal can help "clean" soil or water contaminated with high levels of lead, nickel or other harmful metals. Exploring the possibilities calls for hours of lab work every week for Hope Johnson, assistant professor of biological science, and student researchers.

“Strains of bacteria harmless to humans and animals can be used to oxidize manganese within days, and oxidized manganese will absorb those harmful metals, trap them within its chemical web by binding them at the electron level, and turn them into harmless sediment. In soil, it prevents the metals from ever reaching the water table,” Johnson said.

Polluted underground aquifers might benefit from the technique, Johnson said, because the bacteria-manganese combination can reach places conventional methods may not.

“Water headed down to the underground aquifer could be seeded with manganese and bacteria,” she said, in contrast to most current remediation techniques. Those involve pumping water up for treatment or drilling to the aquifers to inject chemicals. Time-consuming and expensive, those tasks only work on aquifers small enough to treat, said Johnson. Some underground aquifers spread for hundreds of miles.

That bacteria oxidize manganese and other metals has long been known, Johnson said. “But how and why they do so is poorly understood. My students and I are focused on a better understanding, with an eye to how the knowledge will lead to better remediation.”

Johnson's work is supported by $5,000 in start-up funds from the College of Natural Science and Mathematics until she can secure a National Science Foundation grant.

“Manganese oxides recently were found to interact with prions, a protein particle similar to a virus and a vector in mad cow and other neurological wasting diseases. They also interact with hormones," Johnson said.

Hormones enter the water from improperly disposed medications, the urine of humans and animals treated with hormones and medications, as well as other sources. Current filtering and cleaning processes don’t remove all of the hormones, she noted. Tiny, but constant, amounts remain. Once in the drinking water, they are consumed by the public, she said. Some scientists point their research at removal of those hormones with oxidized manganese. Manganese-oxide research, while relatively new, has produced a lot of literature, but that knowledge needs to be transformed into application, she said.

Early Interest

Johnson's concern for the environment began early — she was so young she doesn’t remember exactly when — and grew as she earned a master’s degree in environmental engineering at Stanford, where she took a microbiology course and was hooked.

“I thought it was so awesome that life could be described by redox reactions,” the researcher said, referring to reduction-oxidation processes in which oxygen plays a part in converting one chemical to another. That is what happens when living bodies turn food into energy, what happens to manganese when it is oxidized and, in turn, what it does to minerals, prions and hormones. Because of that experience, her doctoral degree included an emphasis in microbiology.

"Being a scientist affects the way I see and comprehend the world, and that permeates all the courses I teach," said Johnson. "I'm deeply fascinated with the incredible metabolic diversity of bacteria and with the fact that we can understand that diversity on a very basic molecular level. I constantly look forward to sharing that with my students."

Johnson takes that enthusiasm into the genetics and molecular biology class she teaches, as well as into her lab. “I’m trying to get across the importance of critical thinking and problem solving,” she said, two indispensable aspects of conducting good science.

Senior biological science major Ralph Gozun, a member of her research team, considers her teaching a success.

“Dr. Johnson guides us in our experiments and, in the process, helps us refine our approaches. I learned from her new and creative ways to design experiments. There's nothing like getting good results in the lab, a huge sense of accomplishment. But, I’m also learning patience, because it’s possible to get inconclusive results even after several trials. You learn all the time, including from your own mistakes.”

Gozun wants to go to graduate school, but which of two career interests he’ll follow is less certain: physical therapy or physician assistant. Either way, “this research will have a definite impact because … working with Dr. Johnson has honed my critical-thinking skills. As a result, I also communicate better with other scientists and have a greater appreciation for them and their work ethic."

He surprised himself, Gozun said, when he found he also communicates better with non-scientists, an ability he thought he might lose. "When non-science major friends ask me what I do in the lab, I can explain so they understand it and they get really interested.

"I think the key is to explain as you would in normal life," Gozun stressed. "You don't tell them, 'I'm trying to determine ligand-receptor specificity,' you tell them, 'I'm trying to figure out if cells communicate with each other using special signals.'

"I do this research because it’s sort of my way of giving back to my field by expanding the knowledge that will be passed on to the next generation of science majors,” added Gozun, who lives in Fullerton.

Johnson, also a Fullerton resident, joined the university in August. She previously held a scientific associate position with the Joint Center for Structural Genomics at the Scripps Research Institute, where she focused on understanding protein function in microorganisms that grow in geothermically heated water.