Resistance of Blastocystis to chlorine and hydrogen peroxide

10.1007/s00436-022-07713-2Parasitology Research1221167-17

The Mitochondrion-Related Organelles of Blastocystis

Blastocystis is an anaerobic microbial eukaryote that inhabits the gut of various animals. While it was considered to be a parasite, its pathogenicity is controversial, since recent estimations suggest that Blastocystis could be present in more than one billion humans. Blastocystis belongs to the stramenopiles (heterokonts), a diverse group of eukaryotes that also include unicellular diatoms and giant multicellular kelps. The Blastocystis cell lacks typical features of other stramenopiles, its genome has laterally acquired many genes from other prokaryotes and eukaryotes, resulting in having exceptional biochemistry and unique adaptations of its mitochondria. For example, Blastocystis mitochondrion-related organelles (MROs) have characteristics of typical mitochondria, including Complex I and II from electron transport chain, mitochondrial DNA, Fe-S cluster assembly and amino acid metabolism, but also proteins that are typically present in obligate anaerobes including FeFe-Hydrogenase, pyruvate metabolism and alternative oxidase. Some of the pathways have been localized and biochemically characterized, providing a better understanding on the functions of these organelles. In this chapter, we will present and examine the status quo regarding the biology and morphology of Blastocystis MROs and we will discuss future avenues on exploring even further adaptations of these organelles

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

Large-scale comparative metagenomics of Blastocystis, a common member of the human gut microbiome

The influence of unicellular eukaryotic microorganisms on human gut health and disease is still largely unexplored. Blastocystis spp. commonly colonize the gut, but its clinical significance and ecological role are currently unsettled. We have developed a high-sensitivity bioinformatic pipeline to detect Blastocystis subtypes (STs) from shotgun metagenomics, and applied it to 12 large data sets, comprising 1689 subjects of different geographic origin, disease status and lifestyle. We confirmed and extended previous observations on the high prevalence the microrganism in the population (14.9%), its non-random and ST-specific distribution, and its ability to cause persistent (asymptomatic) colonization. These findings, along with the higher prevalence observed in non-westernized individuals, the lack of positive association with any of the disease considered, and decreased presence in individuals with dysbiosis associated with colorectal cancer and Crohn’s disease, strongly suggest that Blastocystis is a component of the healthy gut microbiome. Further, we found an inverse association between body mass index and Blastocystis, and strong co-occurrence with archaeal organisms (Methanobrevibacter smithii) and several bacterial species. The association of specific microbial community structures with Blastocystis was confirmed by the high predictability (up to 0.91 area under the curve) of the microorganism colonization based on the species-level composition of the microbiome. Finally, we reconstructed and functionally profiled 43 new draft Blastocystis genomes and discovered a higher intra subtype variability of ST1 and ST2 compared with ST3 and ST4. Altogether, we provide an in-depth epidemiologic, ecological, and genomic analysis of Blastocystis, and show how metagenomics can be crucial to advance population genomics of human parasites