The aim of this work is to introduce and to test the hypothesis that pH-dependent self-oxidation of dead organic matter by its own respiratory electron transport system /ETS/ can be an important alternative process to active decomposition by microorganisms. An important event of the pH-dependent self-oxidation is the opening of cell walls and envelopes of decaying cells providing free opportunity for equilibration the internal and external pH.
The ETS-activity of homogenates of living planktonic organisms and sediments derived from alkaline Lake Balaton /pH=8.4-8.6/ and that of Sphagnum moss from an acidic peat bog /pH=3.9-4.1/ showed uniformity pH-dependence of respiratory enzyme system in vitro, demonstrating that there is no adaptation in enzymatic level to the pH of environment. In an other set of experiments, where decaying Selenastrum capricornUtum Prinz cultures were incubated in axenic conditions at pH=5.4 and pH=8.4, ETS-activity and changes in C of the samples at low pH were minimal. At or high pH a considerably high initial ETS-activity was found which decreased exponentially in time parallel with the exponential decrease of Corg content of the samples. C content of these samples stabilised 5 weeks after the org beginning of the experiment at 19.5% of the original value.
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