Ward Home

Department of Geosciences 
M51 Guyot Hall 
Princeton University 
Princeton, NJ 08544
Phone: (609) 258-5150
Fax: (609) 258-0796
E-Mail:bbw@princeton.edu

Research (Project Summaries)

Marine and global nitrogen cycle, molecular and immunological probes for marine bacteria and bacterial processes (especially nitrification and denitrification), microbal ecology, xenobiotic transformations by bacterial communities.

Microbes control many of the important biogeochemical processes that occur in the oceans as well as on land.  They contribute to the trace gas cycles that influence climate; they utilize and produce nutrients that are involved in eutrophication; and they are even capable of cleansing the environment by degrading a vast variety of chemical compounds, both naturally occurring and anthropogenically produced.  My research focuses on the nitrogen cycle and the microorganisms involved in transformations of inorganic and organic nitrogen in the ocean and in sediment environments.  This research makes use of technical approaches that range from molecular biological techniques to stable isotope biogeochemistry.   The two main bacterial groups we study are the nitrifiers, autotrophs which oxidize ammonium to nitrite and nitrate, and the denitifiers, heterotrophs which can respire nitrate in the absence of oxygen.  The linked activities of these two groups can be crucial in determining the chemical form and supply of nitrogen to planktonic communities and in determining the net nitrogen budget of ecosystems.

We have used molecular methods for identification and analysis of bacteria in natural systems to study the distribution and diversity of nitrifying and denitrifying bacteria in marine environments. One ongoing project utilizes PCR and gene probe analysis to detect nitrifying bacteria in sediments and seawater, and to characterize the bacterial community across spatial and seasonal gradients.  Our objective is to understand how the rates of nitrification may depend on the species composition of the nitrifying bacterial assemblage and its variation over time, space and environmental conditions.  Another project uses genetic techniques to identify the kinds of microorganisms that are responsible for nitrate and ammonium assimilation in seawater.  The field work for these two projects is carried out in Monterey Bay, California, and in estuarine environments on the California Coast.

It has recently been recognized that trace metals such as iron and zinc are essential for plant and algal nutrition and that the availability of these metals may limit primary production.  By contrast, very little is known about the trace metal requirements or toxicities for bacteria, which is the motivation behind another current project.  Our study site is a permanently ice-covered lake in Antarctica which has two separate lobes; denitrification occurs in one lobe but not the other.  We hypothesize that trace metal limitation or toxicity might explain this phenomenon.  Trace metals are required for most of the redox chemistry of bacterial processes, and we are approaching this general area of research initially through study of the denitrifying enzymes.

This research program (Project Summaries)  is supported by field work on research cruises and expeditions as well as by laboratory based research, and is supported by a variety of federal and regional funding agencies.

Recent Extramural Projects
 

2003-2006 National Science Foundation: What limits denitrification and bacterial growth in Lake Bonney, Taylor Valley, Antarctica?

2000-2005 National Science Foundation: Biocomplexity of Aquatic Microbial Systems: Relating Diversity of Microorganisms to Ecosystem Function. 

2000-2003 Department of Energy: The Coupling Between Carbon and Nitrogen Cycles in Coastal Upwelling Ecosystems: Biogeochemical Cyling and Its Molecular Basis.

1998-2001 National Science Foundation:  Control of Dentrification in a Permanently Ice Covered Antarctic Lake:  Potential for Regulation by Bioactive Metals.  (Co-PI Mark Wells, UCSC.)

1998-2007  National Science Foundation and Department of Energy:  Environmental Molecular Science Institute for Environmental  Bioinorganic Chemistry (CEBIC) (PI Francois Morel)

1997-1998 Packard Ocean Science and Technology: Analysis of Monterey Bay Sediment Microbial Communities using Ribosomal DNA based Phylogenetic and Sequencing Analysis.

1997-1999 National Oceanoceanographic and Atmospheric Administration: The effect of Methomyl on Nitrification in Elkhorn Slough Sediments.

1997-2000 Department of Energy: Fate of Upwelled Nitrate in Monterey Bay: Biogeochemical Cycling and its Molecular Basis.

1997-2000 National Science Foundation: Community Structure and Activity of Nitrifying Bacteria in Aquatic Environments.

1994-1997 National Science Foundation: Nitrification and Denitrification: Transformation Rates and Molecular Probes for Bacteria in the Nitrogen.

1994-1995 California Department of Fish and Game: Bioremediation Capabilities of Natural Microbial Communities in San Francisco Bay.

1993-1995 National Science Foundation: CHN Analyzer and TOC Analyzer Instrument Grant. (Co-PI with M. Delaney and K. Bruland, Marine Sciences, UCSC)

1993-1996 Office of Naval Research: Bioremediation by microbial mats.

1991-1994 National Science Foundation: The missing nitrogen: The role of dissolved organic nitrogen (DON) in new production.
 

2000-present  Several cruises per year in Chesapeake Bay/Atlantic Ocean

2001 McMurdo Station, Antarctica, 6 weeks, Nov-Dec.

2000 McMurdo Station, Antarctica, 7 weeks, Nov-Dec.

1998-99 Chief Scientist, Bimonthly one-day cruises in Monterey Bay.

1996 R/V Sagar Sampada, Arabian Sea, 13 days, November.

1995 Chief Scientist, R/V New Horizon, Eastern Tropical North Pacific, 28 days, July.