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Entamoeba histolytica infection causes amoebiasis, which is a global public health problem. The major route of infection is oral ingestion of E. histolytica cysts, cysts being the sole form responsible for host-to-host transmission. Cysts are produced by cell differentiation from proliferative trophozoites in a process termed ‘encystation’. Therefore, encystation is an important process from a medical as well as a biological perspective. Previous electron microscopy studies have shown the ultrastructure of precysts and mature cysts; however, the dynamics of ultrastructural changes during encystation were ambiguous. Here, we analysed a series of Entamoeba invadens encysting cells by transmission electron microscopy. Entamoeba invadens is a model for encystation and the cells were prepared by short interval time course sampling from in vitro encystation-inducing cultures. We related sampled cells to stage conversion, which was monitored in the overall population by flow cytometry. The present approach revealed the dynamics of ultrastructure changes during E. invadens encystation. Importantly, the results indicate a functional linkage of processes that are crucial in encystation, such as glycogen accumulation and cyst wall formation. Hence, this study provides a reference for studying sequential molecular events during Entamoeba encystation.

The effect of three proteasome inhibitors, lactacystin, clasto-lactacystin β-lactone, and MG-132, on the growth, encystation, and excystation of Entamoeba histolytica and Entamoeba invadens was examined. All of these drugs blocked E. histolytica growth in a concentration-dependent manner; lactacystin was most potent for the inhibition and MG-132 showed the inhibitory effect only at higher concentrations. E. invadens was more resistant to these drugs than E. histolytica. Encystation of E. invadens was also inhibited and was more sensitive to the drugs than was growth. β-Lactone was the most potent encystation inhibitor. The inhibitory effect of lactacystin and the β-lactone on encystation was slightly and little abrogated by the removal of the drug, respectively. Multinucleation occurred in E. histolytica trophozoites treated with these drugs, being most marked with lactacystin. In contrast, no multinucleation was observed in E. invadens treated with the drugs. Electron microscopy revealed that the treatment of E. histolytica trophozoites with lactacystin led to an increase in the number of cells with many glycogen granules in the cytoplasm. Lactacystin, β-lactone and MG-132 had no or little effect on the excystation and metacystic development of E. invadens. These results suggest that proteasome function plays an important role for Entamoeba growth and encystation, but has no obvious effect on excystation or metacystic development.

Protozoan parasites of the genus Entamoeba infect many classes of vertebrates and are primarily classified based on morphological criteria. To date, only a few species have been proven to cause disease. Here, we examined the pathology of infected pigs with hemorrhage and detected Entamoeba parasites. Isolates were characterized genetically and ultrastructurally to identify the species. Histopathologically, bleeding and thrombus formation were seen only in the large intestine mucosa, where a large number of trophozoites or some Entamoeba cysts were observed around breakdowns in the lamina propria. No screw-shaped bacteria were detected in the lesions, and no pathogenic bacteria such as Brachyspira spp. were detected in fecal cultures. Interestingly, electron microscopy revealed that the parasites possessed mitochondrial organelles, unlike other Entamoeba spp. The isolates were identified as Entamoeba suis by PCR analysis and sequencing of the small subunit ribosomal RNA (SSU rRNA) gene. In phylogenetic analyses based on the actin gene, the E. suis isolate formed a cluster with Entamoeba histolytica and Entamoeba invadens, as well as with other parasites of the Amoebidae. Whether the pathogenicity of the E. suis isolate is affected by the severity of infection or host health status remains unclear; however, our results suggest that E. suis could cause or exacerbate clinical symptoms such as hemorrhagic colitis or diarrhea.

Entamoeba suis and Entamoeba polecki subtypes (ST) 1 and 3 have recently been implicated in disease outbreaks in pigs. However, the distributions of these parasites in Japan and the potential sources of infection on farms still remain unclear. Here, we examined a farm of fattening/growing pigs with abnormal feces in Kagoshima Prefecture, Japan, and found the presence of parasites in the farm environment. Examination of intestinal tissues from pigs presenting with ulcerative colitis revealed a large number of trophozoites that had invaded the lesions. We identified single and mixed infections of E. suis and E. polecki ST1 and ST3 in paraffin sections or fecal samples from affected pigs. Two subtypes of Entamoeba were identified using four primer sets by PCR and sequencing. The parasites were detected in moist soil samples obtained around the drinking water source or puddles, implicating transmission of cysts via contaminated soils. Additionally, we found evidence of Entamoeba spp. and coinfections in surveyed pigs without any diarrhea at two neighboring farms. Our results establish methods for successfully identification of parasites, including cases in which multiple infections are present.

Entamoeba histolytica , an anaerobic protozoan parasite, is the causative agent of amoebiasis, bloody diarrhea, and liver abscesses in humans. Amoebiasis is more predominant in tropical areas with poor sanitation conditions, and it remains the fourth leading cause of death due to a protozoan infection. E. histolytica life cycle spans between an infective ‘cyst stage’ and an active disease-causing ‘trophozoite stage’. We have isolated ribosomes from the trophozoite stage of E. histolytica . Here, we report single particle cryo-EM structures of the 53S ribosome large subunit (LSU), and 75S associated ribosomes, with P-tRNA, A/P and P/E tRNAs, and with paromomycin antibiotic, at 2.8 Å to 3.4 Å resolution. The E. histolytica possesses a reduced ribosome with a conserved core, and the periphery evolved with species-specific unique features. The most notable features are the presence of the rRNA triple helix near the peptide exit tunnel, the expansion segment H88ES102 near the exit site on LSU, and unique insertions in r-proteins. Furthermore, the 75S ribosome paromomycin complex structure provides the atomic details of its interactions. These structures provide insights into the evolutionary adaptation of the E. histolytica translational machinery and may be explored further for amoebicidal therapeutic intervention. Entamoeba histolytica causes bloody diarrhea and liver abscesses in humans. Here, the authors report the cryo-EM structure of E. histolytica ribosomes from its disease-causing, trophozoite state and reveal several unique features, such as the rRNA triple helix motif.

The cytoskeleton is a key component of eukaryotic cells, including protists. It is composed of microtubules, microfilaments, and intermediate filaments. Here, we review the available information on the cytoskeleton of several relevant pathogenic protists, including Trypanosomatidae, Apicomplexa, Trichomonadidae, Giardia intestinalis, and Entamoeba histolytica. In protists, the first two components, made of tubulins and actin, predominate. Usually, they associate with each other and with other components to form complex structures. Emphasis is given to the following structures: flagellum, flagellar-cell body adhesion zone, paraflagellar rod, sub-pellicular microtubules, cytostome, conoid, adhesive disc, funis, median body, costa, axostyle, parabasal filaments, and clockwise filaments. On the other hand, filamentous structures made of not yet completely characterized proteins form structures such as the costa. Each structure is analyzed using morphological information obtained through modern microscopy techniques and biochemical data.

Of the three species of found in swine, namely , and , can also infect humans, producing colitis or abscesses of liver and leading to death. However, the pathogenicity of other species of has not been fully characterized. Here, we conducted histopathology and molecular surveys on a pig farm where piglets had blackish feces or muddy diarrhea. Histopathological examination of two piglets showed necrosis of the mucous surface at the ileum, cecum, or colon, infiltration of neutrophils, and formation of ulcers. Based on morphological characteristics, and trophozoites were mainly detected at lamina propria and surface of the lesion, respectively, and , a bacterial pathogen, was also detected. Molecular analysis using the small subunit ribosomal RNA gene on other piglets and a sow revealed infection with both and . These findings corroborate our previous reports that the two spp. are pathogenic in pigs as aggravations of symptoms with . This is the first report about mixed infection with and

Hydrogenosomes and mitosomes are mitochondrion-related organelles in anaerobic/microaerophilic eukaryotes with highly reduced and divergent functions. The full diversity of their content and function, however, has not been fully determined. To understand the central role of mitosomes in Entamoeba histolytica, a parasitic protozoon that causes amoebic dysentery and liver abscesses, we examined the proteomic profile of purified mitosomes. Using 2 discontinuous Percoll gradient centrifugation and MS analysis, we identified 95 putative mitosomal proteins. Immunofluorescence assay showed that 3 proteins involved in sulfate activation, ATP sulfurylase, APS kinase, and inorganic pyrophosphatase, as well as sodium/sulfate symporter, involved in sulfate uptake, were compartmentalized to mitosomes. We have also provided biochemical evidence that activated sulfate derivatives, adenosine-5'-phosphosulfate and 3'-phosphoadenosine-5'-phosphosulfate, were produced in mitosomes. Phylogenetic analysis showed that the aforementioned proteins and chaperones have distinct origins, suggesting the mosaic character of mitosomes in E. histolytica consisting of proteins derived from α-proteobacterial, δ-proteobacterial, and ancestral eukaryotic origins. These results suggest that sulfate activation is the major function of mitosomes in E. histolytica and that E. histolytica mitosomes represent a unique mitochondrion-related organelle with remarkable diversity.

Background Intestinal parasitosis is one of several health concerns about immigrants who travel from endemic to non-endemic regions. Reliable rapid sensitive diagnostic tools, for use in non-endemic regions, are urgently required to enable frequent assessment of immigrant workers in jobs where risk of local transmission is a particular concern (e.g. food-handlers). We assessed the burden of intestinal protozoa in newly arrived immigrants and those applying for renewal of work permits in Qatar ( n  = 735), by both microscopic examination of stool samples and by Real Time PCR methodology. Results Prevalence was considerably higher using RT-PCR compared with coproscopy ( Blastocystis hominis : 65.2 vs 7.6%; Giardia duodenalis : 14.3 vs 2.9%; Entamoeba histolytica : 1.6 vs 1.2%). Dientamoeba fragilis was sought only by RT-PCR (prevalence of 25.4%). Prevalence of G. duodenalis was significantly higher in male subjects, associated with blue collar workers and declined over time. Prevalence of B. hominis varied significantly with region of origin of subjects with highest values recorded among African immigrants. Prevalence of D. fragilis also varied with region of origin of subjects, and was lower in young female subjects and in renewal applicants compared with first-time applicants for work permits. Conclusions We strongly recommend that, henceforth, intestinal protozoa should be screened by RT-PCR, with a particular focus on frequent assessment of immigrant food-handlers.

Summary The development of amoebiasis is influenced by the expression of the lysine and glutamic acid rich protein 1 (KERP1), a virulence factor involved in Entamoeba histolytica adherence to human cells. Up to date, it is unknown how the protein transits the parasite cytoplasm towards the plasma membrane, specially because this organism lacks a well‐defined endoplasmic reticulum (ER) and Golgi apparatus. In this work we demonstrate that KERP1 is present at the cell surface and in intracellular vesicles which traffic in a pathway that is independent of the ER–Golgi anterograde transport. The intracellular displacement of vesicles enriched in KERP1 relies on the actin‐rich cytoskeleton activities. KERP1 is also present in externalized vesicles deposited on the surface of human cells. We further report the interactome of KERP1 with its association to endomembrane components and lipids. The model for KERP1 traffic here proposed hints for the first time elements of the endocytic and exocytic paths of E. histolytica.