NITRIFICATION AND DENITRIFICATION - PROBING THE NITROGEN-CYCLE IN AQUATIC ENVIRONMENTS

Methods designed to detect microorganisms involved in the biogeochemis try of nitrogen in the marine environment are rapidly being developed and deployed in ecological investigations. Probes based on phylogeneti c sequences (usually rRNA) and those based on the sequences of-functio nal genes or proteins have both been demonstrated in the nitrogen cycl e. The most progress has been made for ammonia oxidizers; several sets of PCR primers have been described and their specificity may be optim ized to allow detection of genetically and ecologically meaningful gro ups. For denitrifying bacteria, functional probes based on nitrite red uctase show most promise. These approaches should complement the more familiar, but no less sophisticated, methods that focus on quantificat ion of in situ transformation rates. Both approaches in combination wi ll be useful in understanding regulation and environmental control of biogeochemical processes.