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Applied and Environmental Microbiology, August 2003, p. 4527-4533, Vol. 69, No. 8
0099-2240/03/$08.00+0     DOI: 10.1128/AEM.69.8.4527-4533.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.

Osmoregulation in the Parasitic Protozoan Tritrichomonas foetus

Sarah L. Maroulis, Philip J. Schofield, and Michael R. Edwards*

School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, New South Wales 2052, Australia

Received 26 December 2002/ Accepted 2 May 2003

Tritrichomonas foetus was shown to undergo a regulatory volume increase (RVI) when it was subjected to hyperosmotic challenge, but there was no regulatory volume decrease after hypoosmotic challenge, as determined by using both light-scattering methods and measurement of intracellular water space to monitor cell volume. An investigation of T. foetus intracellular amino acids revealed a pool size (65 mM) that was similar to that of Trichomonas vaginalis but was considerably smaller than those of Giardia intestinalis and Crithidia luciliae. Changes in amino acid concentrations in response to hyperosmotic challenge were found to account for only 18% of the T. foetus RVI. The T. foetus intracellular sodium and potassium concentrations were determined to be 35 and 119 mM, respectively. The intracellular K+ concentration was found to increase considerably during exposure to hyperosmotic stress, and, assuming that there was a monovalent accompanying anion, this increase was estimated to account for 87% of the RVI. By using light scattering it was determined that the T. foetus RVI was enhanced by elevated external K+ concentrations and was inhibited when K+ and/or Cl- was absent from the medium. The results suggested that the well-documented Na+-K+-2Cl- cotransport system was responsible for the K+ influx activated during the RVI. However, inhibitors of Na+-K+-2Cl- cotransport in other systems, such as quinine, ouabain, furosemide, and bumetanide, had no effect on the RVI or K+ influx in T. foetus.

* Corresponding author. Mailing address: School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, NSW 2052, Australia. Phone: 61-2-9385-2017. Fax: 61-2-9385-1483. E-mail: m.edwards{at}unsw.edu.au.

Applied and Environmental Microbiology, August 2003, p. 4527-4533, Vol. 69, No. 8
0099-2240/03/$08.00+0     DOI: 10.1128/AEM.69.8.4527-4533.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Kleydman, Y., Yarlett, N., Gorrell, T. E. (2004). Production of ammonia by Tritrichomonas foetus and Trichomonas vaginalis. Microbiology 150: 1139-1145 [Abstract] [Full Text]  


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