Fermentation of Purines and their Effect on the Adenylate Energy Charge and Viability of Starved Peptococcus pravotii

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Abstract
The principal products of endogenous metabolism of the obligate anaerobe P. prevotii were CO2, NH3, acetate and butyrate, which are also produced by fermentation of nucleosides, purines and ribose, thus supporting the previous finding that RNA is the only cellular component to undergo substantial degradation under starvation conditions. Minor products were H2, formate and propionate. The stoichiometries of fermentation of xanthine, adenine, adenosine and ribose were determined. The ability to ferment exogenous nucleosides, purines and ribose declined rapidly on starvation, as did the ability to generate ATP from xanthine, and was paralleled by the loss of viability. Addition of pulses of xanthine or adenine to organisms in the early stages of starvation sustained their adenylate energy charge and prolonged their viability. P. prevotii dies when its principal energy source (RNA) is depleted, probably due to the rapid decay of the transport function of the cytoplasmic membrane under these conditions, so that uptake of nutrients is inadequate to support growth on transfer to a recovery medium.