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A broad distribution of the alternative oxidase in microsporidian parasites.

ABSTRACT: Microsporidia are a group of obligate intracellular parasitic eukaryotes that were considered to be amitochondriate until the recent discovery of highly reduced mitochondrial organelles called mitosomes. Analysis of the complete genome of Encephalitozoon cuniculi revealed a highly reduced set of proteins in the organelle, mostly related to the assembly of iron-sulphur clusters. Oxidative phosphorylation and the Krebs cycle proteins were absent, in keeping with the notion that the microsporidia and their mitosomes are anaerobic, as is the case for other mitosome bearing eukaryotes, such as Giardia. Here we provide evidence opening the possibility that mitosomes in a number of microsporidian lineages are not completely anaerobic. Specifically, we have identified and characterized a gene encoding the alternative oxidase (AOX), a typically mitochondrial terminal oxidase in eukaryotes, in the genomes of several distantly related microsporidian species, even though this gene is absent from the complete genome of E. cuniculi. In order to confirm that these genes encode functional proteins, AOX genes from both A. locustae and T. hominis were over-expressed in E. coli and AOX activity measured spectrophotometrically using ubiquinol-1 (UQ-1) as substrate. Both A. locustae and T. hominis AOX proteins reduced UQ-1 in a cyanide and antimycin-resistant manner that was sensitive to ascofuranone, a potent inhibitor of the trypanosomal AOX. The physiological role of AOX microsporidia may be to reoxidise reducing equivalents produced by glycolysis, in a manner comparable to that observed in trypanosomes.

SUBMITTER: Williams BA

PROVIDER: S-EPMC2820529 | biostudies-literature | 2010 Feb

REPOSITORIES: biostudies-literature

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A broad distribution of the alternative oxidase in microsporidian parasites.

Williams Bryony A P BA Elliot Catherine C Burri Lena L Kido Yasutoshi Y Kita Kiyoshi K Moore Anthony L AL Keeling Patrick J PJ

PLoS pathogens 20100212 2

Microsporidia are a group of obligate intracellular parasitic eukaryotes that were considered to be amitochondriate until the recent discovery of highly reduced mitochondrial organelles called mitosomes. Analysis of the complete genome of Encephalitozoon cuniculi revealed a highly reduced set of proteins in the organelle, mostly related to the assembly of iron-sulphur clusters. Oxidative phosphorylation and the Krebs cycle proteins were absent, in keeping with the notion that the microsporidia a ...[more]

PMID: 20169184

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Project description:BACKGROUND:The amphipod and microsporidian diversity in freshwaters of a heterogeneous urban region in Germany was assessed. Indigenous and non-indigenous host species provide an ideal framework to test general hypotheses on potentially new host-parasite interactions, parasite spillback and spillover in recently invaded urban freshwater communities. METHODS:Amphipods were sampled in 17 smaller and larger streams belonging to catchments of the four major rivers in the Ruhr Metropolis (Emscher, Lippe, Ruhr, Rhine), including sites invaded and not invaded by non-indigenous amphipods. Species were identified morphologically (hosts only) and via DNA barcoding (hosts and parasites). Prevalence was obtained by newly designed parasite-specific PCR assays. RESULTS:Three indigenous and five non-indigenous amphipod species were detected. Gammarus pulex was further distinguished into three clades (C, D and E) and G. fossarum more precisely identified as type B. Ten microsporidian lineages were detected, including two new isolates (designated as Microsporidium sp. nov. RR1 and RR2). All microsporidians occurred in at least two different host clades or species. Seven genetically distinct microsporidians were present in non-invaded populations, six of those were also found in invaded assemblages. Only Cucumispora dikerogammari and Dictyocoela berillonum can be unambiguously considered as non-indigenous co-introduced parasites. Both were rare and were not observed in indigenous hosts. Overall, microsporidian prevalence ranged from 50% (in G. roeselii and G. pulex C) to 73% (G. fossarum) in indigenous and from 10% (Dikerogammarus villosus) to 100 % (Echinogammarus trichiatus) in non-indigenous amphipods. The most common microsporidians belonged to the Dictyocoela duebenum- /D. muelleri- complex, found in both indigenous and non-indigenous hosts. Some haplotype clades were inclusive for a certain host lineage. CONCLUSIONS:The Ruhr Metropolis harbours a high diversity of indigenous and non-indigenous amphipod and microsporidian species, and we found indications for an exchange of parasites between indigenous and non-indigenous hosts. No introduced microsporidians were found in indigenous hosts and prevalence of indigenous parasites in non-indigenous hosts was generally low. Therefore, no indication for parasite spillover or spillback was found. We conclude that non-indigenous microsporidians constitute only a minimal threat to the native amphipod fauna. However, this might change e.g. if C. dikerogammari adapts to indigenous amphipod species or if other hosts and parasites invade.

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A broad distribution of the alternative oxidase in microsporidian parasites.

Publications

A broad distribution of the alternative oxidase in microsporidian parasites.

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