Abstract
A method is presented to measure respiratory electron transport system (ETS) activity in marine sediments. To prepare cell-extracts a mechanical Braun-Melsungen homogenizer, Model MSK, is used. The ETS assay procedure is carried out with NADH, NADPH and succinate as electron donors and with INT as electron acceptor. Triton X-100 in the reaction mixture makes extraction of formazan in organic solvents not necessary. With the method described not only aerobic but also anaerobic mineralization by sulphate reduction is measured, as was demonstrated with pure cultures of Desulfovibrio. The effect of homogenization time, enzyme concentration, incubation time, substrate concentration and temperature on the ETS activity was studied. The Michaelis-Menten constant K m for NADH as substrate appeared to be 0.044 mM. For the temperature range between 20° C and 30° C the activation energy was found to be 5.4 kcal.mol −1, the Q 10 = 1.4.
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