Aquatic Sciences Meeting, Albuquerque 2001

SS14 Microbial Diversity (Disciplinary Connections)

Date: Monday, February 12, 2001, Time: 4:45:00 PM

Location: Brazos

Casciotti, K, L, Princeton University, Princeton, USA, cascioti@princeton.edu

Sigman, D, M, Princeton University, Princeton, USA, sigman@princeton.edu

Ward, B, B, Princeton University, Princeton, USA, bbw@princeton.edu

MOLECULAR AND BIOGEOCHEMICAL SIMILIARITY OF NITRITE REDUCTASE IN NITRIFYING AND DENITRIFYING BACTERIA

The reduction of NO2- by nitrifying bacteria is an important source of NO and N2O in aquatic ecosystems. We have previously demonstrated, using molecular techniques, the presence of a gene for copper-containing nitrite reductase (nirK) in ammonia-oxidizing bacteria that is very similar to the nirK of classical denitrifying bacteria. In this study, the kinetic isotope effects for nitrite reduction were determined for several ammonia-oxidizing bacteria possessing the copper-containing nitrite reductase. These are compared to the isotope effects we measure for NO2- reduction by two classical denitrifiers: Pseudomonas aureofaciens (which possesses the copper-NiR) and Pseudomonas chlororaphis (which possesses the cd-heme NiR). The isotope effects for NO2- reduction by organisms possessing the copper-containing nitrite reductase were found to be very similar, regardless of the organism (nitrifier or denitrifier), whereas the isotope effect for the cd-heme NiR in P. chlororaphis was significantly different. This study thus extends the known similarity of the copper-containing nitrite reductase in nitrifying and denitrifying bacteria from a molecular level to a biogeochemically relevant level and underscores potential biogeochemical differences between the copper- and heme-containing dissimilatory nitrite reductases.

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Aquatic Sciences Meeting, Albuquerque 2001

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