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Microbiology 146 (2000), 3245-3250
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Microbiology (2000), 146, 3245-3250.
© 2000 Society for General Microbiology

Bioenergetics and Transport

Continuous monitoring of the cytoplasmic pH in Methanobacterium thermoautotrophicum using the intracellular factor F420 as indicator

Peter von Felten1 and Reinhard Bachofen1

Institute of Plant Biology, University of Zürich, Zollikerstraße 107, CH-8008 Zürich, Switzerland1

Author for correspondence: Reinhard Bachofen. Tel: +41 1 634 82 80. Fax: +41 1 634 82 04. e-mail: bachofen{at}botinst.unizh.ch

The absorption spectrum of factor F420 changes depending on the pH and the redox state of the cytoplasm. Specific wavelengths were used to calibrate absorption changes to allow the measurement of changes in the cytoplasmic pH in Methanobacterium thermoautotrophicum. Upon a hydrogen pulse, a rapid efflux of protons was observed. Under these energized conditions, the {Delta}pH amounts to 0·2–0·4 pH units at pH 6·6, and 0·6–0·8 pH units at pH 6·0. It decays within 10–20 s. In parallel, a sodium gradient is formed which has a slightly longer lifetime. Both {Delta}pH and {Delta}{Psi} contribute to the proton-motive force present during methanogenesis. The energy-conversion rate, as indicated by the decay of the energized state of the cell, is fastest under growth conditions, i.e. at pH 6·9 and at a temperature of 58 °C.

Keywords: cytoplasm, pH gradient, intracellular pH, protonmotive force, methanogenic bacteria

Abbreviations: BESA, bromoethanesulfonic acid; CF, carboxyfluorescein; TCS, tetrachlorosalicylanilide




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L. M. I. de Poorter, W. J. Geerts, and J. T. Keltjens
Hydrogen concentrations in methane-forming cells probed by the ratios of reduced and oxidized coenzyme F420
Microbiology, May 1, 2005; 151(5): 1697 - 1705.
[Abstract] [Full Text] [PDF]


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