Section 26
Chapter 25,165

On the metabolism of the purple sulphur bacteria in organic media

Muller, F.M.

Archiv Mikro Biol 4(2): 131-166


DOI: 10.1007/bf00407535
Accession: 025164239

Purple sulphur bacteria were able to develop in media containing only 1 simple N-free organic compound, in absence of oxidizable S compounds. Radiant energy was indispensable for development in these media. In a chem. investigation of the metabolism in cultures containing lactate, pyruvate, acetate, succinate, malate or butyrate as the organic substrate, practically no metabolic products other than relatively small amounts of CO2 were detected; in the butyrate cultures CO2 was taken up instead of being formed. By determining the C content of the bacterial substance synthesized in the cultures, it was shown that the substrate is probably completely converted into cell material and CO2, i.e., that assimilation predominates in metabolism. Differences in the amt. of CO2 formed (or taken up) per unit of substrate consumed in cultures with different substrates are caused by the different oxidation values of the various substrates, the av. oxidation value of cell material being approximately the same with all substrates. Since a consideration of assimilation in general leads to the view that the most of the organic cell constituents are formed from the substrate via pyruvic acid, the ways in which this acid can be formed from the various substrates used in the exps. are discussed. Conversion of the substrates into pyruvic acid involves 1 or more de-hydrogenations; a consideration of the H acceptors which may effect this dehydrogenation shows that CO2 must play a prominent part as an acceptor in this process. It is thus concluded that photosynthetic processes are involved in the metabolism of the purple sulphur bacteria in organic media. In the equation for photosynthesis in general: CO2 + 2H2A [forward arrow] CH2O + 2A + H2O, H2A may now be replaced by organic substances as well as by H2S or H2O.

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