Chapter

Anoxia

Volume 21 of the series Cellular Origin, Life in Extreme Habitats and Astrobiology pp 83-112

Date:

Hydrogenosomes and Mitosomes: Mitochondrial Adaptations to Life in Anaerobic Environments

  • Rob M. De GraafAffiliated withDepartment of Evolutionary Microbiology, Faculty of Science, Radboud University Nijmegen Email author 
  • , Johannes H. P. HacksteinAffiliated withDepartment of Evolutionary Microbiology, Faculty of Science, Radboud University Nijmegen

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Abstract

The adaptation of unicellular eukaryotes to life under permanently anaerobic conditions involves substantial changes in mitochondrial morphology and metabolism. The analysis of 16 independently arisen adaptations reveals that losses of genes of the organellar genome initiate a pathway that eventually leads to the complete loss of the genome. Simultaneously, the mitochondrial electron transport chain undergoes changes that lastly lead to a complete loss of the subunits and the loss of the ability to generate ATP by using a proton gradient. In addition, many genes found in textbook mitochondria become lost, leading to a rainbow of mitochondrion-derived organelles with characteristic proteomes. These derived organelles are named hydrogenosomes if they generate hydrogen and ATP, and mitosomes if they produce neither of the two. In essence, these organelles are mitochondria that adapted to life under anaerobic conditions by reductive evolutionary tinkering.