AME 73:235-243 (2014)  -  DOI: https://doi.org/10.3354/ame01720

ABSTRACT: Lysis of marine bacteria by viruses releases a range of organic compounds into the environment, including d- and l-amino acids, but the uptake of these compounds by other bacteria is not well characterized. This study determined that Photobacterium sp. strain SKA34 (Gammaproteobacteria) increased in abundance following uptake of d- and l-amino acids from viral lysate of Cellulophaga sp. strain MM#3 (Flavobacteria). Ammonium and dissolved free amino acids were taken up almost to detection limits, suggesting that the C:N ratio of bioavailable organic matter in the lysate was high for Photobacterium sp. growth, thus causing a net uptake of ammonium. In contrast, only 1.51 µmol l^-1 of the 4.77 µmol l^-1 of the total dissolved combined amino acids (DCAAs) were taken up, indicating that a fraction of lysate-derived DCAAs were semi-labile or refractory to bacterial uptake. Both d- and l-amino acid uptake rates were approximately proportional to their concentrations, indicating similar availability for each enantiomer and unsaturated uptake rates. These results imply that under high C:N conditions, both d-amino acids (mainly found in bacterial cell walls) and l-amino acids (found in proteins of the rest of the cell) are equally available for bacterial growth, and support arguments that viruses are key players in marine nitrogen cycling.

KEY WORDS: Viral lysis · Marine bacteria · Amino acid · Nitrogen · Uptake · Nutrient cycling · Ammonium