THE BREN SCHOOL OF Environmental Science & Management
at the University of California, Santa Barbara

Presents

Christopher Francis
Department of Environmental Earth System Science
Stanford University

"Ammonia-Oxidizing Archaea:

An Important New Player in the Microbial Nitrogen Cycle"

Hosted by Professor Patricia Holden

Abstract

Nitrification—the microbial oxidation of ammonia to nitrate via nitrite—plays a critical role in nitrogen cycling and removal in aquatic systems. Despite its biogeochemical importance, however, surprisingly little is known regarding how the distribution, diversity, and abundance of nitrifying communities are influenced by key environmental factors. Although the first and rate-limiting step of nitrification—ammonia oxidation—was long believed to be carried out exclusively by ammonia-oxidizing bacteria (AOB), the recent discovery of ammonia-oxidizing archaea (AOA) indicates that our understanding of the microbial ecology of nitrification requires careful re-evaluation. This seminar will highlight our recent work utilizing amoA genes (encoding ammonia monooxygenase subunit A) as molecular markers to assess the relative importance of AOA and AOB communities across physical/chemical gradients in marine and estuarine systems.

Biography

Chris Francis received his PhD in Marine Biology from Scripps Institution of Oceanography (UC San Diego) in 2000. His thesis research focused on characterizing the diversity and mechanisms of metal-cycling bacteria. He then moved to Princeton University, where, as an NSF postdoctoral fellow in Microbial Biology and a Hess Fellow in Geosciences, the focus of his research shifted to the molecular ecology of uncultivated N-cycling microbial communities in a variety of aquatic ecosystems. In 2003 he joined the faculty of the School of Earth Sciences at Stanford University, where his research is currently centered on the molecular, biogeochemical, and ecological aspects of ammonia-oxidizing and denitrifying communities in coastal and estuarine systems, including San Francisco Bay, Elkhorn Slough, Huntington Beach, and the Gulf of California.

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