METABOLIC ADAPTATION IN NATURAL BACTERIAL-POPULATIONS SUPPLEMENTED WITH SELECTED AMINO-ACIDS

Amino acids at concentrations of 10·0 μm induced abrupt increases in the rates of uptake and degradation of amino acids by coastal plankton communities. Treatment of the communities with erythromycin, an inhibitor of protein synthesis in bacteria, prevented the increase. The induced uptake was restricted to a group of amino acids that depended upon the amino acid initially supplied. A rapid, transitory increase in the concentration of ATP coincided with the increases in the rates of uptake and degradation of l-arginine and l-glutamate. Uptake rates measured in separate short-term incubations increase markedly after a 60 h lag in a sample exposed to l-arginine and then decrease slowly during the 180 h following the complete depletion of the substrate in the sample (at 64 h). When more l-arginine was added to the sample a second marked increase in l-arginine uptake rates occurred after a 12 h lag. The duration of the initial lag correlated with the incubation temperature. These results suggest that the bacteria in these communities respond to relatively large increases in amino acid concentrations through metabolic adaptation or activation involving the synthesis of inducible enzymes. © 1979.