Fermentation of purines and their effect on the adenylate energy charge and viability of starved Peptococcus prévotii.

The principal products of endogenous metabolism of the obligate anaerobe Peptococcus prévotii were carbon dioxide, ammonia, acetate and butyrate, which are also produced by fermentation of nucleosides, purines and ribose, thus supporting our previous finding that RNA is the only cellular component to undergo substantial degradation under starvation conditions. Minor products were hydrogen, formate and propionate. The stoicheiometries 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. However, addition of pulses of xanthine or adenine to organisms in the early stages of starvation sustained their adenylate energy charge and prolonged their viability. Evidence suggests that P. prévotii dies when its principal energy source (RNA) is depleted, and a possible explanation is that the transport function of the cytoplasmic membrane decays rapidly under these conditions so that, on transfer to a recovery medium, uptake of nutrients is inadequate to support growth.