This work will use the Nitrite reductase enzyme (NiR) as an indicator of in situ denitrification. The hypothesis that induction of NiR is related to initiation of denitrification in low oxygen regimes will be investigated in continuous culture experiments. This work will develop a set of tools for measurement of species specific growth rates and investigation of the in situ distribution of: 1) denitrifying bacteria, 2) NiR among cells of known denitrifying strains and among the total bacterial population, and 3) the genetic potential for denitrification. Assays for enumeration of denitrifiers, for NiR in bulk samples and inside whole cells, probes for the NiR gene and specific probes for denitrifier ribosomal RNA and ribosomal RNA genes are described. Denitrification is a process in which simple inorganic compounds of nitrogen dissolved in water are converted to dinitrogen gas such as makes up most of our atmosphere. This process is carried out by bacteria and is ubiquitous in both soil and water environments. One important consequence of Denitrication in the water column accounts for about half the annual loss of fixed nitrogen from the marine environment. Little is known of the taxonomic and metabolic diversity of marine nitrifying bacteria, but by analogy to terrestrial systems, marine denitrifiers are probably a diverse and successful group. This study involves the application of state of the art immunological and molecular probes to examine the physical and community distribution, as well as the potential for the production of, a key enzyme in the denitrification pathway-Nitrite Reductase. The objective of these advanced molecular biological techniques is to increase our understand- ing of marine denitrification, a problem that has been resistent to the application of more conventional oceanographic methods.
