Geomicrobiologist Clara Chan holds a sample of iron-oxidizing bacteria in her lab.

NSF Career Award

Geomicrobiologist receives prestigious NSF award for work on iron-microbe interactions


10:01 a.m., Aug. 23, 2012--Patches of orange slime with an oily sheen are not uncommon to see along stream banks, often mistaken for pollution or decomposing leaves. In fact, the substance is made by metal-eating bacteria that create oxidized iron, or rust, naturally in the environment.

University of Delaware geomicrobiologist Clara Chan studies the role of these rust-producing bacteria in water flowing both above and below ground, and she recently received a prestigious Faculty Early Career Development Award from the National Science Foundation (NSF) to expand her research.

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“Microbial iron cycling is important to understanding the chemistry of our waters,” said Chan, assistant professor of geological sciences in the College of Earth, Ocean, and Environment (CEOE).

Certain bacteria get their energy by consuming iron, leaving behind iron oxide minerals as a waste product. In some settings, microscopic strands of the minerals form large orange mats resembling pumpkin pulp.

The bacteria tend to grow where iron from the earth has seeped into water, bringing Chan to examine them in diverse environments. At a flooded mine in Wisconsin, she found the bacteria were helping remove heavy metals from groundwater. Currently, she is researching how they clog wells in a contaminated Colorado aquifer. She is also investigating the bacteria forming huge mats on the deep ocean floor where hydrothermal vents spew iron into the Pacific.

Chan will use her NSF award to study iron-oxidizing microbes that live in groundwater-soaked soil at two nearby locations: a stream bank in White Clay Creek and the Indian River Inlet north of Bethany Beach. Both are sites where iron-rich water underground meets surface water, creating what Chan calls “happy zones” for bacterial growth. The goal is to better understand the conditions in which the bacteria thrive within sediment in these groundwater-surface water transition areas – and how they affect the chemistry and movement of the water.

“Up until now I’ve mostly studied really obvious, large manifestations of oxidizing bacteria in big formations,” Chan said. “The reason that I chose the groundwater-surface water interface is because the water environment is very different, mostly because there is little oxygen.”

The bacteria need oxygen to metabolize iron, but some seem to prefer low-oxygen environments: Less air means a lower likelihood that the iron will rust away abiotically through chemical reactions before the bacteria can get to it.

“The chemistry helps dictate where the bacteria grow,” Chan said. “The bacteria then affect the chemistry in the environment.”

Identifying which bacteria species in the environment are iron-oxidizers has been one of the challenges in Chan’s research, in part because they are slow to culture in the lab, and so far she and other scientists have discovered several dozen. Instead of focusing just on species identification, she is working to find the genetic markers that indicate any given bacteria’s ability to oxidize iron.

Knowing more about the genetics and physiology of these bacteria will not only improve understanding of the environment today, Chan explained, but also gives clues about the past. Geologic evidence shows increased oxygen levels around 2.4 billion years ago, when the oceans were full of iron. Microfossils of iron-oxidizing bacteria dating to that time could tell more about the conditions that gave rise to new life forms – if scientists like Chan can find them. 

“One of the questions I would like to answer in my entire career is, ‘How did Earth’s surface chemistry co-evolve with life?’” Chan said. “And how did life evolve with the environment around it?”

A Louisiana native, Chan graduated from Stanford University in 1997 with a bachelor’s degree in geological and environmental sciences and earned a master’s in civil and environmental engineering the following year. She worked as an environmental engineer for several years before beginning her doctoral studies at University of California, Berkeley. After earning a Ph.D., she was a postdoctoral fellow in marine chemistry and geochemistry at Woods Hole Oceanographic Institution and joined UD in 2009. 

“Clara’s research explores an intersection of geology, chemistry and microbiology,” CEOE Dean Nancy Targett said. “She is an asset to CEOE’s interdisciplinary approach and an excellent teacher for students interested in the way these fields overlap in the environment.” 

About the NSF Career Award

The Faculty Early Career Development Program is the NSF’s most prestigious award “in support of junior faculty who exemplify the role of teacher-scholars through outstanding research, excellent education and the integration of education and research within the context of the mission of their organizations,” according to the foundation’s website.

Chan is the second faculty member in UD’s geological sciences department to receive a Career Award this year, joining hydrogeologist Holly Michael

Article by Teresa Messmore

Photos by Evan Krape and courtesy of Clara Chan

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