Jonathan P. Zehr, Ph.D.

Professor, Department of Ocean Sciences, University of California, Santa CruzJonathan P. Zehr’s website
Portrait photo of Jonathan Zehr

SCOPE-ALOHA Project: Functional Aspects of Microbial Communities in the North Pacific Ocean

Marine microbes play critical roles in marine food webs and maintaining the habitability of the planet. Marine microbial communities are diverse in taxa, but also in biogeochemical functions, which are directly related to the roles of microbes in nutrient cycles and trace gas formation and consumption. The relationships among the dynamic environmental factors and microbial abundances, growth and biogeochemical activity are probably the least understood aspects of complex marine microbial communities, and yet are critical for quantitative, predictive understanding. Nitrogen fixation is a particularly important aspect of oligotrophic, open ocean communities, which maintains the fertility of the oceans, and controls global carbon flux. Nitrogen-fixing microorganisms are only one of many examples of important functional groups in the carbon, nitrogen and sulfur cycle.

Little is known about the temporal and spatial constraints on nitrogen fixation and how these distributions are correlated with the environmental factors that control them. This project will examine the genomic and physiological bases of free-living and symbiotic nitrogen-fixing (and other biogeochemically-important microbial groups) microorganisms and how they relates to growth, distributions and biogeochemical activities in space and time. This collaborative work will form links between microbial community structure, biogeochemical cycles of carbon, nitrogen and phosphorus, in order to develop a better quantitative and predictive framework for understanding microbial processes in the sea.

Jonathan P. Zehr has spent the past 15 years as Professor of Ocean Sciences at the University of California, Santa Cruz, and is Adjunct Scientist at the Monterey Bay Aquarium Research Institute. His research has focused on nitrogen cycling by aquatic microorganisms, although he has publications spanning topics in microbial diversity in freshwater and hypersaline systems, organic matter metabolism, selenium metabolism in estuarine sediments, and nitrogen metabolism in oligotrophic oceans. His major focus has been oceanic nitrogen fixation. Zehr was one of the pioneers in applying molecular biology approaches to study microorganisms involved in biogeochemical cycles by targeting “functional” genes and has developed coupled flow cytometry and genome sequencing techniques, that have led to a number of discoveries, including the unusual nitrogen-fixing symbiotic cyanobacterium UCYN-A. Currently he is developing molecular biological, genomic and transcriptomic tools to examine microbial gene expression from entire microbial communities, and developing molecular probes that can be used to detect genes of organisms remotely in the sea on the Environmental Sample Processor (developed by Chris Scholin, MBARI). Zehr is a Fellow of the American Academy of Microbiology.

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