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BioMed Research International
Volume 2015 (2015), Article ID 437534, 6 pages
Review Article

Stress Management in Cyst-Forming Free-Living Protists: Programmed Cell Death and/or Encystment

Department of Biological and Biomedical Sciences, Aga Khan University, Karachi 74800, Pakistan

Received 8 September 2014; Revised 8 December 2014; Accepted 24 December 2014

Academic Editor: Philippe Holzmuller

Copyright © 2015 Naveed Ahmed Khan et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


In the face of harsh conditions and given a choice, a cell may (i) undergo programmed cell death, (ii) transform into a cancer cell, or (iii) enclose itself into a cyst form. In metazoans, the available evidence suggests that cellular machinery exists only to execute or avoid programmed cell death, while the ability to form a cyst was either lost or never developed. For cyst-forming free-living protists, here we pose the question whether the ability to encyst was gained at the expense of the programmed cell death or both functions coexist to counter unfavorable environmental conditions with mutually exclusive phenotypes.