Kaplan, L.A., and T.L. Bott. 1985. Freshwater Biology 15:133–138.
- The adenylate energy charge (ECA) of microbial communities from streambed sediments was measured during three different seasons, under experimental manipulation and in culture.
- The ECA values of sediments (x±S.E.) in the autumn, winter and spring were low and constant; 0.22±0.03 (n=12), 0.32±0.04 (n= 12) and 0.28±0.03 (n=6) respectively.
- A 5 h exposure of sediments to an algal lysate at 3.0–4.0°C and a 48 h exposure of sediments to tryptone-yeast extract at 8.0–18.0°C failed to increase ECA even though respiration increased 3.7-fold during the latter exposure.
- The cellular ECA of a bacterial monoculture, sampled in log phase, was 0.90±0.10 (n=3), but extracellular AMP depressed the total culture ECA to 0.21±0.01 (n=4).
- Attempts to isolate extracellular AMP from the interstitial waters of sediments were unsuccessful.
- The data suggest that under natural conditions ECA is of limited use as a monitor of subtle changes in the physiological state of microbial communities in streambed sediments.