f Oxygen and the Growth and Metabolism of Clostridium acetobutylicum
- Authors: R. W. O'BRIEN*, J. G. MORRIS†
- First Published Online: 01 November 1971, Microbiology 68: 307-318, doi: 10.1099/00221287-68-3-307
- Subject: Physiology And Growth
- Issue Published:
Summary: Clostridium acetobutylicum has been studied during batch cultivation at pH 7 and 35° in a glucose + casein hydrolysate + vitamins and salts medium kept (i) anaerobic (E h, – 400 to – 370 mV), (ii) aerated (E h, – 50 to 0 mV; dissolved O2, < 1 μM), and (iii) aerobic (E h, + 100 mV; dissolved O2, 40 to 50 μM). Short-term (4 to 6 h.) exposure to oxygen was not lethal, though at sufficiently high concentrations oxygen decreased the rate of glucose consumption, halted growth and prevented net synthesis of DNA, RNA and protein. Under these aerobic conditions the organism was drained of ‘reducing power’ and starved of energy – as evidenced by cessation of butyrate formation (but not of acetate production), and by a marked fall in intracellular ATP. These consequences of oxygenation were swiftly reversed when anaerobic conditions were re-established; ‘normal’ growth and glucose metabolism then resumed. There was no evidence of H2O2 production, nor could the effects of oxygenation be attributed merely to its elevation of the culture E h. Thus oxygen (40 μM) inhibited growth even in a medium poised with dithiothreitol at – 50 mV, while growth and glucose metabolism continued unchecked when the E h of an anaerobic culture was maintained at +370 mV by addition of potassium ferricyanide.
Present address: Department of Biochemistry, University of Sydney, Sydney, N.S.W., Australia.
Present address: Department of Botany and Microbiology, University College of Wales, Aberystwyth.
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