Multiphasic Kinetics for D-Glucose Uptake by Assemblages of Natural Marine Bacteria

Abstract

D-glucose-6-( super(3)H) uptake kinetics for marine microbial assemblages were multiphasic when the kinetics were determined over a broad concentration range (10 super(-9) M to 10 super(-3) M). Maximum uptake velocity (V sub(max)) and the sum of half saturation constant (K sub(t)) and ambient glucose concentration (S sub(n)), (K sub(t) + S sub(n)), increased gradually as the range of glucose concentration was increased. In all seawater samples examined the lowest (K sub(t) + S sub(n)) values were 2-5 x 10 super(-9) M; highest values were as high as 5.9 x 10 super(-4) M. Simple diffusion into algae or bacteria cannot explain the non-linearity of kinetics curves. Removal of most algal cells did not change the kinetic pattern, and indirect estimates of diffusion into bacteria were too small to have greatly changed the uptake in 1 x 10 super(-9) - 1 x 10 super(-5) M range of glucose. The kinetic diversity of marine bacterial assembleges has implications in the cycling of dissolved organic matter in the varied concentration regimes presumably present in production microzones.