Mitochondrial glycolysis in a major lineage of eukaryotes

This is the author accepted manuscript. The final version is freely available from OUP via the DOI in this recordThe establishment of the mitochondrion is seen as a transformational step in the origin of eukaryotes. With the mitochondrion came bioenergetic freedom to explore novel evolutionary space leading to the eukaryotic radiation known today. The tight integration of the bacterial endosymbiont with its archaeal host was accompanied by a massive endosymbiotic gene transfer resulting in a small mitochondrial genome which is just a ghost of the original incoming bacterial genome. This endosymbiotic gene transfer resulted in the loss of many genes, both from the bacterial symbiont as well the archaeal host. Loss of genes encoding redundant functions resulted in a replacement of the bulk of the host's metabolism for those originating from the endosymbiont. Glycolysis is one such metabolic pathway in which the original archaeal enzymes have been replaced by the bacterial enzymes from the endosymbiont. Glycolysis is a major catabolic pathway that provides cellular energy from the breakdown of glucose. The glycolytic pathway of eukaryotes appears to be bacterial in origin, and in well-studied model eukaryotes it takes place in the cytosol. In contrast, here we demonstrate that the latter stages of glycolysis take place in the mitochondria of stramenopiles, a diverse and ecologically important lineage of eukaryotes. Although our work is based on a limited sample of stramenopiles, it leaves open the possibility that the mitochondrial targeting of glycolytic enzymes in stramenopiles might represent the ancestral state for eukaryotes.TAW is supported by a Royal Society University Research Fellowship and NERC grant NE/P00251X/1. Work in the lab of MvdG was supported by Wellcome Trust grant 078566/A/05/Z. PGK wishes to acknowledge support by the German Research Foundation (DFG, grant KR 1661/6-1) and the Gordon and Betty Moore Foundation GBMF 4966 (grant DiaEdit)

Exploring the biology and evolution of Blastocystis and its role in the microbiome

Blastocystis is a microbial eukaryote, considered to be the most prevalent microbe colonizing the human gut, colonising approximately one billion individuals worldwide. Although Blastocystis presence has been linked to intestinal disorders, its pathogenicity still remains controversial due to its high prevalence in asymptomatic carriers. Having 17 genetic subtypes, Blastocystis is extremely diverse and can withstand fluctuations of oxygen in the gut. Blastocystis harbors peculiar mitochondrion-related organelles (MROs), which are considered to be an intermediate form between a typical aerobic mitochondrion and an obligate anaerobic hydrogenosome. Another interesting fact about Blastocystis concerns its mixed genome: 2.5% of the Blastocystis proteins have been laterally acquired from eukaryotes and prokaryotes. These acquired genes are associated with carbohydrate scavenging and metabolism, anaerobic amino acid and nitrogen metabolism, oxygen-stress resistance, and pH homeostasis. In addition, Blastocystis has proteins associated with secretion that are potentially involved in infection, escaping host defense and even affect composition of the prokaryotic microbiome and inflammation of the gut. In this chapter, we will challenge the state-of-the-art on Blastocystis knowledge, and we will present published data that can be used to understand the genomic adaptations of this microbial organism and its role within the microbiome of the hosts