CORE Metadata, citation and similar papers at core.ac.uk Provided by e-Prints Soton The Journal of Experimental Biology 208, 2569-2579 2569 Published by The Company of Biologists 2005 doi:10.1242/jeb.01660 Life at acidic pH imposes an increased energetic cost for a eukaryotic acidophile Mark A. Messerli1,2,*, Linda A. Amaral-Zettler1, Erik Zettler3,4, Sung-Kwon Jung2, Peter J. S. Smith2 and Mitchell L. Sogin1 1The Josephine Bay Paul Center for Comparative Molecular Biology and Evolution, Marine Biological Laboratory, Woods Hole, MA 02543, USA, 2BioCurrents Research Center, Program in Molecular Physiology, Marine Biological Laboratory, Woods Hole, MA 02543, USA, 3Sea Education Association, PO Box 6, Woods Hole, MA 02543, USA and 4Centro de Biología Molecular, Universidad Autónoma de Madrid, Cantoblanco, Madrid 28049, Spain *Author for correspondence (e-mail:
[email protected]) Accepted 25 April 2005 Summary Organisms growing in acidic environments, pH·<3, potential difference of Chlamydomonas sp., measured would be expected to possess fundamentally different using intracellular electrodes at both pH·2 and 7, is close molecular structures and physiological controls in to 0·mV, a rare value for plants, animals and protists. The comparison with similar species restricted to neutral pH. 40·000-fold difference in [H+] could be the result of either We begin to investigate this premise by determining the active or passive mechanisms. Evidence for active magnitude of the transmembrane electrochemical H+ maintenance was detected by monitoring the rate of ATP gradient in an acidophilic Chlamydomonas sp. (ATCC® consumption. At the peak, cells consume about 7% more PRA-125) isolated from the Rio Tinto, a heavy metal ATP per second in medium at pH·2 than at pH·7.