PROJECT SUMMARY

Traditionally, the importance of inorganic nitrogen (N) for the nutrition and growth of marine phytoplankton has been recognized, while inorganic N utilization by bacteria has historically received less attention. However, accumulating evidence suggests that bacteria compete with phytoplankton for nitrate (NO3-) and that heterotrophic bacteria may have a profound effect on the flux of N, and therefore carbon (C), in ocean margins. Unfortunately, the processes that regulate the assimilation of NO3- by bacteria are not well understood because it is difficult to differentiate between bacterial and phytoplankton N uptake using conventional tracer techniques. This is critical because sinks for dissolved N that do not incorporate inorganic C represent mechanisms which reduce the drawdown of CO2 via the "biological pump".

Since 1997, with the support of the DOE Biotechnology Investigations - Ocean Margins Program, we have developed molecular tools (PCR and RT-PCR primer sets) that allow us to selectively isolate, characterize, and study the diversity and genetic expression (mRNA) of the structural gene responsible for the assimilation of NO3- by heterotrophic bacteria (nasA). To date, our studies have revealed that bacteria capable of assimilating NO3- are ubiquitous in marine waters and that the expression of nasA can be regulated in model organisms by the concentration of NH4+. Furthermore, through this project we have made exciting strides towards institutionalizing a research and education based collaboration between the Skidaway Institute of Oceanography and Savannah State University, an historically black university within the University System of Georgia.

Continuation of this project enhances the development of molecular tools for studying the role of heterotrophic bacterial utilization of NO3- and uses these tools in conjunction with new molecular methods (T-RFLP and quantitative PCR) to investigate the factors regulating bacterial NO3- utilization in diverse ocean margin environments, the nature of the competition between heterotrophic bacteria and phytoplankton for NO3-, and the functional importance of the existence of diverse bacterial populations capable of utilizing NO3-. These studies build on the progress achieved during the past few years and take advantage of the research team and collaborations that are currently in place.

The results of this study are continuing to provide new molecular methods to address questions relative to the utilization of NO3- by bacteria and the underlying mechanisms that control NO3- flux into bacteria. In addition, the program provides a framework for the continuation and expansion of relationships between the Skidaway Institute of Oceanography and Savannah State University. Specifically we intend to vigorously support the implementation of a new graduate program in marine science at Savannah State University through the research proposed. There is no doubt that if this program is successful, it will serve as an important and sustainable mechanism to increase the number of under represented scientists (African Americans, Hispanic Americans, Pacific Island Americans and American Indians) in the field of marine sciences.