Additional Participants

Graduate Student

Carolyn Weber

Project Period

August 2006-July 2007

Level of Access

Open-Access Report

Grant Number


Submission Date



Bacteria play an important role in the global budget of carbon monoxide (CO). Largely unknown bacterial populations in soils and the water column of aquatic systems oxidize hundreds of teragrams per year, or about 10%-20% of the estimated annual flux to the atmosphere. In spite of their biogeochemical significance, relatively little is known about the identity of CO-oxidizing populations active in situ, their phylogenic and physiological diversity or the importance of CO as substrate for their basic metabolic needs. of CO oxidizers. It is clear that CO at high concentrations (> 1000 ppm) can serve as a sole source of cell carbon and energy for laboratory-grown cultures, but ambient CO concentrations seldom reach or exceed a few ppm. Bacteria readily use such concentrations, but are they sufficient to contribute significantly to cellular metabolic needs?

This award supports Professor Gary M. King and one of his graduate students at the University of Maine to collaborate in research on this question with Dr. Y. M. Kim and his research group from Yonsei University in Korea. They will evaluate the significance of low, ecologically realistic CO concentrations for growth and survival of two common soil isolates, Mycobacterium smegmatis and Bradyrhizobium japonicum. This collaborative project will include both molecular and physiological analyses of the ability of CO at low concentrations to promote the survival and viability of CO oxidizers under conditions relevant to their natural dynamics in soils. Dr. Kim has extensive experience with the molecular biology, physiology and growth of CO-oxidizing bacteria, including mycobacteria, and characterization of the genetics and biochemistry of CO dehydrogenase, while Dr. King has extensive experience in studying the ecophysiology and biogeochemistry of microbial trace gas utilization, analytical techniques and instrumentation for near-ambient CO analyses, and expertise in the design of microcosms and gas flow systems for research.

Broader significance

Results of the study will significantly improve our understanding of the ecophysiology of microbial CO metabolism, particularly at real-world levels. This information is an important factor in predicting potential responses to long-term, regional-scale disturbances in climate, land use and eutrophication of aquatic systems.

The work will involve exchanges of both U.S. and Korean graduate students, who will benefit from learning new research techniques and from the cultural experience. The international research experience is likely to expand the future research opportunities of the US students in Dr. King's group. The exchange of techniques and methods in this research partnership will enhance the capabilities of both labs to address topical issues in the ecophysiology of microbial groups that affect atmospheric composition.