Evolutionary analysis of cellular reduction and anaerobicity in the hyper-prevalent gut microbe Blastocystis.

Blastocystis is the most prevalent microbial eukaryote in the human and animal gut, yet its role as commensal or parasite is still under debate. Blastocystis has clearly undergone evolutionary adaptation to the gut environment and possesses minimal cellular compartmentalization, reduced anaerobic mitochondria, no flagella, and no reported peroxisomes. To address this poorly understood evolutionary transition, we have taken a multi-disciplinary approach to characterize Proteromonas lacertae, the closest canonical stramenopile relative of Blastocystis. Genomic data reveal an abundance of unique genes in P. lacertae but also reductive evolution of the genomic complement in Blastocystis. Comparative genomic analysis sheds light on flagellar evolution, including 37 new candidate components implicated with mastigonemes, the stramenopile morphological hallmark. The P. lacertae membrane-trafficking system (MTS) complement is only slightly more canonical than that of Blastocystis, but notably, we identified that both organisms encode the complete enigmatic endocytic TSET complex, a first for the entire stramenopile lineage. Investigation also details the modulation of mitochondrial composition and metabolism in both P. lacertae and Blastocystis. Unexpectedly, we identify in P. lacertae the most reduced peroxisome-derived organelle reported to date, which leads us to speculate on a mechanism of constraint guiding the dynamics of peroxisome-mitochondrion reductive evolution on the path to anaerobiosis. Overall, these analyses provide a launching point to investigate organellar evolution and reveal in detail the evolutionary path that Blastocystis has taken from a canonical flagellated protist to the hyper-divergent and hyper-prevalent animal and human gut microbe.

Repurposing in vitro approaches for screening anti-parasitic drugs against the brain-eating amoeba Naegleria fowleri.

Naegleria fowleri is both a pathogenic and a free-living microbial eukaryote, responsible for the development of primary amoebic meningoencephalitis (PAM) in humans. PAM is a rapid, severe and fatal underestimated infectious disease, which has been reported in countries with warmer climates. The major drawbacks with PAM are the lack of effective therapies and delay in diagnosis. The current frontline treatment presents a low rate of recovery (5%) and severe adverse effects. For example, many drug candidates lack efficacy, since they do not effectively cross the blood-brain-barrier. Consequently, more effective drugs are urgently needed. Herein, we report a new in vitro method suitable for medium- and high-throughput drug discovery assays, using the closely related Naegleria gruberi as a model. We have subsequently used this method to screen a library of 1175 Food and Drug Administration-approved drugs. As a result, we present three drugs (camptothecin, pyrimethamine, and terbinafine) that can be repurposed, and are anticipated to readily cross the blood-brain-barrier with activity against Naegleria species in therapeutically achievable concentrations. Successively, we integrated several in vitro assays that resulted in identifying fast-acting and high amoebicidal drugs. In conclusion, we present a new approach for the identification of anti-Naegleria drugs along with three potential drug candidates for further development for the treatment of PAM.

Establishing a Metabolite Extraction Method to Study the Metabolome of Blastocystis Using NMR.

Blastocystis is an opportunistic parasite commonly found in the intestines of humans and other animals. Despite its high prevalence, knowledge regarding Blastocystis biology within and outside the host is limited. Analysis of the metabolites produced by this anaerobe could provide insights that can help map its metabolism and determine its role in both health and disease. Due to its controversial pathogenicity, these metabolites could define its deterministic role in microbiome's "health" and/or subsequently resolve Blastocystis' potential impact in gastrointestinal health. A common method for elucidating the presence of these metabolites is through 1H nuclear magnetic resonance (NMR). However, there are currently no described benchmarked methods available to extract metabolites from Blastocystis for 1H NMR analysis. Herein, several extraction solvents, lysis methods and incubation temperatures were compared for their usefulness as an extraction protocol for this protozoan. Following extraction, the samples were freeze-dried, re-solubilized and analysed with 1H NMR. The results demonstrate that carrying out the procedure at room temperature using methanol as an extraction solvent and bead bashing as a lysis technique provides a consistent, reproducible and efficient method to extract metabolites from Blastocystis for NMR.

Identification and characterisation of a cryptic Golgi complex in Naegleria gruberi.

Although the Golgi complex has a conserved morphology of flattened stacked cisternae in most eukaryotes, it has lost the stacked organisation in several lineages, raising the question of what range of morphologies is possible for the Golgi. In order to understand this diversity, it is necessary to characterise the Golgi in many different lineages. Here, we identify the Golgi complex in Naegleria, one of the first descriptions of an unstacked Golgi organelle in a non-parasitic eukaryote, other than fungi. We provide a comprehensive list of Golgi-associated membrane trafficking genes encoded in two species of Naegleria and show that nearly all are expressed in mouse-passaged N. fowleri cells. We then study distribution of the Golgi marker (Ng)CopB by fluorescence in Naegleria gruberi, identifying membranous structures that are disrupted by Brefeldin A treatment, consistent with Golgi localisation. Confocal and immunoelectron microscopy reveals that NgCOPB localises to tubular membranous structures. Our data identify the Golgi organelle for the first time in this major eukaryotic lineage, and provide the rare example of a tubular morphology, representing an important sampling point for the comparative understanding of Golgi organellar diversity.This article has an associated First Person interview with the first author of the paper.

A cell culture platform for Cryptosporidium that enables long-term cultivation and new tools for the systematic investigation of its biology.

Cryptosporidium parasites are a major cause of diarrhoea that pose a particular threat to children in developing areas and immunocompromised individuals. Curative therapies and vaccines are lacking, mainly due to lack of a long-term culturing system of this parasite. Here, we show that COLO-680N cells infected with two different Cryptosporidium parvum strains produce sufficient infectious oocysts to infect subsequent cultures, showing a substantial fold increase in production, depending on the experiment, over the most optimistic HCT-8 models. Oocyst identity was confirmed using a variety of microscopic- and molecular-based methods. This culturing system will accelerate research on Cryptosporidium and the development of anti-Cryptosporidium drugs.

Acquired resistance to oxaliplatin is not directly associated with increased resistance to DNA damage in SK-N-ASrOXALI4000, a newly established oxaliplatin-resistant sub-line of the neuroblastoma cell line SK-N-AS.

The formation of acquired drug resistance is a major reason for the failure of anti-cancer therapies after initial response. Here, we introduce a novel model of acquired oxaliplatin resistance, a sub-line of the non-MYCN-amplified neuroblastoma cell line SK-N-AS that was adapted to growth in the presence of 4000 ng/mL oxaliplatin (SK-N-ASrOXALI4000). SK-N-ASrOXALI4000 cells displayed enhanced chromosomal aberrations compared to SK-N-AS, as indicated by 24-chromosome fluorescence in situ hybridisation. Moreover, SK-N-ASrOXALI4000 cells were resistant not only to oxaliplatin but also to the two other commonly used anti-cancer platinum agents cisplatin and carboplatin. SK-N-ASrOXALI4000 cells exhibited a stable resistance phenotype that was not affected by culturing the cells for 10 weeks in the absence of oxaliplatin. Interestingly, SK-N-ASrOXALI4000 cells showed no cross resistance to gemcitabine and increased sensitivity to doxorubicin and UVC radiation, alternative treatments that like platinum drugs target DNA integrity. Notably, UVC-induced DNA damage is thought to be predominantly repaired by nucleotide excision repair and nucleotide excision repair has been described as the main oxaliplatin-induced DNA damage repair system. SK-N-ASrOXALI4000 cells were also more sensitive to lysis by influenza A virus, a candidate for oncolytic therapy, than SK-N-AS cells. In conclusion, we introduce a novel oxaliplatin resistance model. The oxaliplatin resistance mechanisms in SK-N-ASrOXALI4000 cells appear to be complex and not to directly depend on enhanced DNA repair capacity. Models of oxaliplatin resistance are of particular relevance since research on platinum drugs has so far predominantly focused on cisplatin and carboplatin.