Journal of Eukaryotic Microbiology最新文献

Since the advent of sequencing techniques and due to their continuous evolution, it has become easier and less expensive to obtain the complete genome sequence of any organism. Nevertheless, to elucidate all biological processes governing organism development, quality annotation is essential. In genome annotation, predicting gene structure is one of the most important and captivating challenges for computational biology. This aspect of annotation requires continual optimization, particularly for genomes as unusual as those of microsporidia. Indeed, this group of fungal-related parasites exhibits specific features (highly reduced gene sizes, sequences with high rate of evolution) linked to their evolution as intracellular parasites, requiring the implementation of specific annotation approaches to consider all these features. This review aimed to outline these characteristics and to assess the increasingly efficient approaches and tools that have enhanced the accuracy of gene prediction for microsporidia, both in terms of sensitivity and specificity. Subsequently, a final part will be dedicated to postgenomic approaches aimed at reinforcing the annotation data generated by prediction software. These approaches include the characterization of other understudied genes, such as those encoding regulatory noncoding RNAs or very small proteins, which also play crucial roles in the life cycle of these microorganisms.

The phylum Parabasalia includes very diverse single-cell organisms that nevertheless share a distinctive set of morphological traits. Most are harmless or beneficial gut symbionts of animals, but some have turned into parasites in other body compartments, the most notorious example being Trichomonas vaginalis in humans. Parabasalians have garnered attention for their nutritional symbioses with termites, their modified anaerobic mitochondria (hydrogenosomes), their character evolution, and the wholly unique features of some species. The molecular revolution confirmed the monophyly of Parabasalia, but considerably changed our view of their internal relationships, prompting a comprehensive reclassification 14 years ago. This classification has remained authoritative for many subgroups despite a greatly expanded pool of available data, but the large number of species and sequences that have since come out allow for taxonomic refinements in certain lineages, which we undertake here. We aimed to introduce as little disruption as possible but at the same time ensure that most taxa are truly monophyletic, and that the larger clades are subdivided into meaningful units. In doing so, we also highlighted correlations between the phylogeny of parabasalians and that of their hosts.

While metopids (Armophorea: Metopida) represent the most species-rich group of free-living anaerobic ciliates thriving in hypoxic environments, our understanding of their true diversity remains incomplete. Most metopid species are still characterized only morphologically. Particularly, the so-called IAC clade (named in the past after some of the taxa included, Idiometopus, Atopospira, and Clevelandellida), comprising free-living members as well as the endosymbiotic ones (order Clevelandellida), is in serious need of revision. In our study, we establish a new free-living genus in the IAC clade, Pidimetopus n. gen., with descriptions of two new species, P. nanus n. sp., and P. permonicus n. sp., using up-to-date molecular and morphologic methods. The genus is characterized by small cells (up to 75 μm long), not more than 10 adoral membranelles and eight somatic kineties, and usually, four long caudal cilia that can stiffen. In addition to morphologic and molecular characterizations, we also conducted a statistical morphotype analysis of the polymorphic species P. nanus n. sp. We discuss the relevance of the earlier morphologically described species Metopus minor as a putative collective taxon for several small metopids less than 50 μm long.

Microsporidia and Apicomplexa are eukaryotic, single-celled, intracellular parasites with huge public health and economic importance. Typically, these parasites are studied separately, emphasizing their uniqueness and diversity. In this review, we explore the huge amount of genomic data that has recently become available for the two groups. We compare and contrast their genome evolution and discuss how their transitions to intracellular life may have shaped it. In particular, we explore genome reduction and compaction, genome expansion and ploidy, gene shuffling and rearrangements, and the evolution of centromeres and telomeres.

Paramecium exhibits responsive behavior to environmental changes, moving either closer to or further away from stimuli. Electrophysiological experiments have revealed that these behavioral responses are controlled by membrane potentials. Anoctamin, a Ca²⁺-activated Cl⁻ channel, is involved in the regulation of membrane potential in mammals. However, it remains uncertain whether Cl⁻ channels like anoctamin regulate Paramecium behavior. Herein, replacement of external Cl⁻ ions with acetate ion and application of Cl⁻ channel blocker niflumic acid (NFA, 0.1 μM) increased spontaneous avoiding reactions (sARs). Hence, we hypothesized that anoctamin is involved in the stabilization of membrane potential fluctuation. Paramecium cells in which the anoctamin-like protein 1 gene was knocked down displayed frequent sARs in the culture medium without external stimulation. Treatment of anoctamin-like protein 1-knockdown cells with the Ca²⁺ chelator BAPTA or Ca-channel blocker nicardipine reversed the increase in sARs. Electrophysiological experiments revealed extension of membrane depolarization when positive currents were applied to anoctamin-like protein 1-knockdown cells. We concluded that anoctamin-like protein 1 works as a Cl-channel and stabilizes the membrane potential oscillation, reducing sARs.

The salamander, Ambystoma annulatum, is considered a “species of special concern” in the state of Arkansas, USA, due to its limited geographic range, specialized habitat requirements and low population size. Although metazoan parasites have been documented in this salamander species, neither its native protists nor microbiome have yet been evaluated. This is likely due to the elusive nature and under-sampling of the animal. Here, we initiate the cataloguing of microbial associates with the identification of a new heterlobosean species, Naegleria lustrarea n. sp. (Excavata, Discoba, Heterolobosea), isolated from feces of an adult A. annulatum.

The nematode Caenorhabditis elegans is an invaluable host model for studying infections caused by various pathogens, including microsporidia. Microsporidia represent the first natural pathogens identified in C. elegans, revealing the previously unknown Nematocida genus of microsporidia. Following this discovery, the utilization of nematodes as a model host has rapidly expanded our understanding of microsporidia biology and has provided key insights into the cell and molecular mechanisms of antimicrosporidia defenses. Here, we first review the isolation history, morphological characteristics, life cycles, tissue tropism, genetics, and host immune responses for the four most well-characterized Nematocida species that infect C. elegans. We then highlight additional examples of microsporidia that infect related terrestrial and aquatic nematodes, including parasitic nematodes. To conclude, we assess exciting potential applications of the nematode-microsporidia system while addressing the technical advances necessary to facilitate future growth in this field.

The phylogenetic and taxonomic affinities of lineages currently assigned to the non-monophyletic ciliate order Loxocephalida Jankowski (1980) within subclass Scuticociliatia Small (1967) remain unresolved. In the current study, we redescribe the morphology of the type species, Loxocephalus luridus Eberhard (1862) based on two Czech populations and include the first scanning and transmission electron microscopy images of the species. We provide the first 18S rRNA gene sequences for L. luridus and consider its phylogenetic position. Our results support the separation of Dexiotricha from Loxocephalus; however, the former genus is recovered as non-monophyletic. The monophyly of genus Dexiotricha and that of Loxocephalus + Dexiotricha is rejected. Loxocephalus luridus, together with Dexiotricha species, nests within a fully supported clade with Conchophthirus species, long presumed to belong to the Pleuronematida. Haptophrya is recovered as sister to this clade. The monophyly of the Astomatia Schewiakoff (1896) including Haptophrya is rejected. No clear morphologic synapomorphy is identified for the fully supported clade consisting of Haptophrya, Dexiotricha, Loxocephalus, and Conchophthirus.

Microsporidia are obligate intracellular parasites of the Fungal Kingdom that cause widespread infections in nature, with important effects on invertebrates involved in food production systems. The two microsporidian species Vairimorpha (Nosema) ceranae (and the less common Vairimorpha (Nosema) apis) can cause individual disease in honey bees and contribute to colony collapse. The efficacy, safety, and availability of fumagillin, the only drug currently approved to treat microsporidia infection in bees, is uncertain. In this review, we will discuss some of the most promising alternative strategies for the mitigation of Vairimorpha spp. with an emphasis on infection by V. ceranae, now the dominant species infecting bees. We will focus on pharmacologic interventions where the mechanism of action is known and examine both pathogen-directed and host-directed approaches. As limiting toxicity to host cells has been especially emphasized in treating bees that are already facing numerous stressors, strategies that disrupt pathogen-specific targets may be especially advantageous. Therefore, efforts to increase the knowledge and tools for facilitating the discovery of such targets and pharmacologic agents directed against them should be prioritized.

The microbiome is the collection of microbes that are associated with a host. Microsporidia are intracellular eukaryotic parasites that can infect most types of animals. In the last decade, there has been much progress to define the relationship between microsporidia and the microbiome. In this review, we cover an increasing number of reports suggesting that microsporidia are common components of the microbiome in both invertebrates and vertebrates. These microsporidia infections can range from mutualistic to pathogenic, causing several physiological phenotypes, including death. Infection with microsporidia often causes a disruption in the normal microbiome, with both increases and decreases of bacterial, fungal, viral, and protozoan species being observed. This impact on the microbiome can occur through upregulation and downregulation of innate immunity as well as morphological changes to tissues that impact interactions with these microbes. Other microbes, particularly bacteria, can inhibit microsporidia and have been exploited to control microsporidia infections. These bacteria can function through regulating immunity, secreting anti-microsporidia compounds, and, in engineered versions, expressing double-stranded RNA targeting microsporidia genes. We end this review by discussing potential future directions to further understand the complex interactions between microsporidia and the other members of the microbiome.