The effects of various water-sample treatments on the apparent uptake of glutamic acid by natural marine microbial populations

Abstract

The apparent glutamate utilization by natural marine microbial populations was shown to be greatly influenced by the method used to terminate the uptake reaction. There was a significant difference in the amount of labeled material associated with the microorganisms when treated with either acid or buffered formaldehyde before the sample was assayed. A comparison of the data collected from acidified and nonacidified water samples resulted in significant differences in the following calculated values: percentage respired, the maximum velocity of uptake (V_max), the turnover time (T_t), and the transport constant and natural substrate concentration (K_t + S_n). The rates of radioactivity incorporation into CO₂ and acidified and nonacidified cells were followed with time and were found to be nonlinear after extended incubation.Data is presented which indicate that the labeled material that is released during acidification is that associated with the glutamate pool. The effects of these observations on the interpretation of data collected during heterotrophic potential studies are discussed.