Acetate uptake by aquatic bacterial communities measured by autoradiography and filterable radioactivity1

In a pulp mill waste aeration lagoon with a high organic content including measurable amounts of acetate, community uptake of acetate followed Michaelis‐Menten kinetics at concentrations of added acetate up to 30 µg ml−1. The measured in situ substrate level, Sn, was <6% to 46% of the K + Sn value calculated from the Michaelis‐Menten equation. Autoradiography was used to determine the uptake kinetics of individual bacterial cells. Two morphologically distinct bacterial types followed Michaelis‐Menten kinetics, but one was at least four times more active in situ. Comparison of several different cell types indicated a minimum uptake activity range of 20‐fold. A few cell types did not absorb acetate. Different cells of the same type showed a 10‐fold range of activity, and the activity per cell did not follow a Poisson distribution.