Nitrogen regeneration during the degradation of several amino acids by plankton communities collected near Halifax, Nova Scotia, Canada

Abstract

Nitrogen regeneration accompanying the bacterial degradation of a variety of amino acids supplied at 10.0 μM to samples of coastal plankton communities collected near Halifax, Nova Scotia, Canada was examined. A lag period characterized by a low rate of amino acid uptake and ammonia release was typically followed by a dramatic increase in the rates of uptake and ammonia release. The duration of the lag period varied with the amino acid tested. The ratio of the final ammonia concentration to the nitrogen supplied as amino acid was taken as the regeneration ratio. This value varied from 0.58 to 0.86 for L-arginine and 0.38 to 1.17 for the other amino acids tested, with an average value of 0.74. The presence of inorganic fixed nitrogen at 10.0 μM had no effect on the degradation of L-arginine. Other organic compounds supplied at 10.0 μM decreased the lag period for L-arginine uptake and degradation. Glucose supplied at 50.0 μM decreased the nitrogen regeneration ratio, but did not further decrease the lag for L-arginine degradation. Carbon respiration ratios for L-arginine, L-glutamate, and L-lysine were 0.70, 0.68, and 0.65 when the nitrogen regeneration ratios were 0.86, 0.38, and 0.77, respectively.