In our research we investigate molecular microbial metabolism and its linkage to ecological and evolutionary processes. We explore the distinguishing features of novel microbial metabolism and how molecular and biochemical differences in metabolism shape microbial fitness. We study novel microbial metabolism with relevance to bioremediation, bioenergy, and intestinal microbiology.
1) Microbial Electrosynthesis and Electron Transport between Microbes and Surfaces
Some microbes have the the capacity to either derive metabolic electrons from redox-active mineral surfaces or transfer such electrons to these surfaces. These processes are of great relevance to geochemical, environmental, but also bioenergy processes. We are investigating the molecular bases of such novel electron transfer to uncover the enzymes and pathways for electron uptake. More recently, we began to explore microbial electrosynthesis as a novel means to produce CO2-neutral biofuels and commodity chemicals.
2) Microbial Reductive Dehalogenation
Chloroethenes, such as PCE and TCE, are the most prevalent groundwater contaminants in the U.S. and the developed countries. Large scale remediation of contaminated aquifers relies largely on the activity of a group of unusual microbes (Dehalococcoides) that derive energy from reductive dehalogenation. We study reductive dehalogenases and the strictly anaerobic bacteria, such as Dehalococcoides mccartyj and Shewanella, on a biochemical, physiological, genomic, and population level to better understand the unprecedented biochemistry of the coenzyme B 12-containing reductive dehalogenases. We also use this information to improve chlorethene bioremediation. Population-level studies in our lab have been revealing speciation and niche adaptation in Dehalococcoides mccartyj. in response to subtle changes in physical-chemical environments.
3) Biofilms and the emergence of antibiotic tolerance and antibiotic resistance
For the last decade, we have been investigating the mechanism of biofilm formation in medically important microorganisms, including Vibrio chloreae, Pseudomonas aeruginosa, Francisella tularensis, and Shewanella oneidensis. We discovered that the stability of biofilms requires cellular energy, and that extracellular matrix material may have a supportive role. In more recent studies, we developed the first system to examine the pharmacokinetics and pharmacodynamics of Pseudomonas aeruginosa biofilms. We investigate the effect of human simulated concentrations of meropenem and tobramycin, administered singly, and in combination, on biofilms of P. aeruginosa PAO1 and clinical isolates from patients with CF, as well as the effect of human simulated concentrations of meropenem and tobramycin, administered singly, and in combination, on biofilms of P. aeruginosa PAO1 and clinical CF isolates.
4) Microbial Metabolic Processes in the Large Intestine
Irritable Bowel Syndrome (IBS) is a chronic, episodic gastrointestinal disorder that is characterized by abdominal pain and altered bowel habits. IBS prevalence is estimated to be 10-15% in Western countries comprising 25 to 50 percent of all referrals to gastroenterologists. The gastrointestinal tract harbors a complex and diverse microbial community, which plays important roles in host nutrition, immune function, health and disease, and it is hypothesized the IBS disease phenotype is associated with a change in colonic microbiota and/or host factors such as mucosal function and immunity. With our physician collaborator, we study the metabolic processes in the intestinal microbial community, and how cellular metabolism is controlled by the host mucosa.
Honors & Awards
Elected Fellow, American Academy of Microbiology (2013)
Otto Moensted Visiting Professor, Danish Technical University, Lyngby, DK (2003)
Research Award, Charles Lee Powell Foundation (2000)
CAREER Award, National Science Foundation (1998)
Visiting Professor, Department of Biochemistry and Biological Process Institute, University of Minnesota (1997)
Terman Fellowship Award, Stanford University (1995)
Postdoctoral Fellowship, Deutsche Forschungsgemeinschaft (1990)
Planetary Biology Internship Fellowship, NASA Life Sciences (Marine Biological Laboratory) (1986)
Dr. rer. nat., Philipps-University, Marburg (1989)