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Original Research ARTICLE Provisionally accepted The full-text will be published soon. Notify me

Front. Cell. Infect. Microbiol. | doi: 10.3389/fcimb.2018.00371

The human gut colonizer Blastocystis respires using Complex II and alternative oxidase to buffer transient oxygen fluctuations in the gut

  • 1University of Kent, United Kingdom
  • 2Defence Science and Technology Laboratory, United Kingdom
  • 3University of Sussex, United Kingdom
  • 4University of Exeter, United Kingdom

Blastocystis is the most common eukaryotic microbe in the human gut. It is linked to irritable bowel syndrome (IBS), but its role in disease has been contested considering its widespread nature. This organism is well adapted to its anoxic niche and lacks typical eukaryotic features such as a cytochrome-driven mitochondrial electron transport. Although generally considered a strict or obligate anaerobe, its genome encodes an alternative oxidase. Alternative oxidases are energetically wasteful enzymes as they are non-protonmotive and energy is liberated in heat, but they are considered to be involved in oxidative stress protective mechanisms. Our results demonstrate that the Blastocystis cells themselves respire oxygen via this alternative oxidase thereby casting doubt on its strict anaerobic nature. Inhibition experiments using alternative oxidase and Complex II specific inhibitors clearly demonstrate their role in cellular respiration. We postulate that the alternative oxidase in Blastocystis is used to buffer transient oxygen fluctuations in the gut and that it likely is a common colonizer of the human gut and not causally involved in IBS. Additionally the alternative oxidase could act as a protective mechanism in a dysbiotic gut and thereby explain the absence of Blastocystis in established IBS environments.

Keywords: Alternative oxidase (AOX), Blastocystis, Oxygen, complex II, intestine, Salicylhydroxamic acid (SHAM), Octyl gallate, thenoyltrifluoroacetone (TTFA)

Received: 15 Jun 2018; Accepted: 03 Oct 2018.

Edited by:

Katherine Ralston, University of California, Davis, United States

Reviewed by:

Elisa Azuara-Liceaga, Universidad Autónoma de la Ciudad de México, Mexico
Alena Zikova, Biology Centre (ASCR), Czechia
Juan Pablo Pardo, Universidad Nacional Autónoma de México, Mexico  

Copyright: © 2018 Tsaousis, Hamblin, Elliot, Young, Rosell Hidalgo, Gourlay, Moore and van der Giezen. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Dr. Mark van der Giezen, University of Exeter, Exeter, United Kingdom,