Morphological and molecular biological characterization of Pleistophora aegyptiaca sp. nov. infecting the Red Sea fish Saurida tumbil

Global marine microbial diversity and its potential in bioprospecting

The past two decades has witnessed a remarkable increase in the number of microbial genomes retrieved from marine systems1,2. However, it has remained challenging to translate this marine genomic diversity into biotechnological and biomedical applications3,4. Here we recovered 43,191 bacterial and archaeal genomes from publicly available marine metagenomes, encompassing a wide range of diversity with 138 distinct phyla, redefining the upper limit of marine bacterial genome size and revealing complex trade-offs between the occurrence of CRISPR-Cas systems and antibiotic resistance genes. In silico bioprospecting of these marine genomes led to the discovery of a novel CRISPR-Cas9 system, ten antimicrobial peptides, and three enzymes that degrade polyethylene terephthalate. In vitro experiments confirmed their effectiveness and efficacy. This work provides evidence that global-scale sequencing initiatives advance our understanding of how microbial diversity has evolved in the oceans and is maintained, and demonstrates how such initiatives can be sustainably exploited to advance biotechnology and biomedicine.

Microsporidian Pathogens of Aquatic Animals

Around 57.1% of microsporidia occupy aquatic environments, excluding a further 25.7% that utilise both terrestrial and aquatic systems. The aquatic microsporidia therefore compose the most diverse elements of the Microsporidia phylum, boasting unique structural features, variable transmission pathways, and significant ecological influence. From deep oceans to tropical rivers, these parasites are present in most aquatic environments and have been shown to infect hosts from across the Protozoa and Animalia. The consequences of infection range from mortality to intricate behavioural change, and their presence in aquatic communities often alters the overall functioning of the ecosystem.In this chapter, we explore aquatic microsporidian diversity from the perspective of aquatic animal health. Examples of microsporidian parasitism of importance to an aquacultural ('One Health') context and ecosystem context are focussed upon. These include infection of commercially important penaeid shrimp by Enterocytozoon hepatopenaei and interesting hyperparasitic microsporidians of wild host groups.Out of ~1500 suggested microsporidian species, 202 have been adequately taxonomically described using a combination of ultrastructural and genetic techniques from aquatic and semi-aquatic hosts. These species are our primary focus, and we suggest that the remaining diversity have additional genetic or morphological data collected to formalise their underlying systematics.

Mechanics of Microsporidian Polar Tube Firing

As obligate intracellular parasites with reduced genomes, microsporidia must infect host cells in order to replicate and cause disease. They can initiate infection by utilizing a harpoon-like invasion organelle called the polar tube (PT). The PT is both visually and functionally a striking organelle and is a characteristic feature of the microsporidian phylum. Outside the host, microsporidia exist as transmissible, single-celled spores. Inside each spore, the PT is arranged as a tight coil. Upon germination, the PT undergoes a large conformational change into a long, linear tube and acts as a tunnel for the delivery of infectious cargo from the spore to a host cell. The firing process is extremely rapid, occurring on a millisecond timescale, and the emergent tube may be as long as 20 times the size of the spore body. In this chapter, we discuss what is known about the structure of the PT, the mechanics of the PT firing process, and how it enables movement of material from the spore body.

Experimental Horizontal Transmission of Enterospora nucleophila (Microsporea: Enterocytozoonidae) in Gilthead Sea Bream (Sparus aurata)

Enterospora nucleophila is a microsporidian enteroparasite that infects mainly the intestine of gilthead sea bream (Sparus aurata), leading to an emaciative syndrome. Thus far, the only available information about this infection comes from natural outbreaks in farmed fish. The aim of the present study was to determine whether E. nucleophila could be transmitted horizontally using naturally infected fish as donors, and to establish an experimental in vivo procedure to study this host-parasite model without depending on natural infections. Naïve fish were exposed to the infection by cohabitation, effluent, or intubated either orally or anally with intestinal scrapings of donor fish in four different trials. We succeeded in detecting parasite in naïve fish in all the challenges, but the infection level and the disease signs were always milder than in donor fish. The parasite was found in peripheral blood of naïve fish at 4 weeks post-challenge (wpc) in oral and effluent routes, and up to 12 wpc in the anal transmission trial. Molecular diagnosis detected E. nucleophila in other organs besides intestine, such as gills, liver, stomach or heart, although the intensity was not as high as in the target tissue. The infection tended to disappear through time in all the challenge routes assayed, except in the anal infection route.

Pseudokabatana alburnus n. gen. n. sp., (Microsporidia) from the liver of topmouth culter Culter alburnus (Actinopterygii, Cyprinidae) from China

We describe the type species of a novel genus of microsporidian parasite, Pseudokabatana alburnus n. gen. n. sp., infecting the liver of topmouth culter, Culter alburnus Basilewsky, 1855, from Lake Poyang off Xingzi county, Jiangxi Province, China. The parasite elicits formation of spherical xenomas of up to 1.2 mm in diameter containing all observed life stages from early merogonal plasmodia to mature spores contained within the cytoplasm of host hepatocytes. Merogonal plasmodia existed in direct contact with the host cytoplasm and contained up to 20 visible nuclei. Plasmotomy of the multinucleate plasmodium led to formation of uninucleate cells in which the nucleus underwent further division to form bi-nucleate presporonts, sporonts (defined by cells with a thickened endospore) and eventually sporoblasts (containing pre-cursors of the spore extrusion apparatus). Mature spores were pyriform and monokaryotic, measuring 2.3 ± 0.19 μm long and 1.3 ± 0.10 μm wide. Spores possessed a bipartite polaroplast and 5-6 coils of a polar filament, in a single rank. The obtained partial SSU rRNA gene sequence, 1383 bp in length, did not match any of microsporidia available in GenBank. SSU rDNA-based phylogenetic analysis indicated a new taxon branching with Kabatana rondoni, a parasite infecting the skeletal muscle of Gymnorhamphichthys rondoni from the Amazon River. Due to different host and tissue tropism, the novel taxon did not fit the diagnostic criteria for the genus Kabatana. Further, based on SSU rDNA-inferred phylogenetic analyses, different ultrastructural features of developmental stages, and ecological considerations, a new genus Pseudokabatana and type species Pseudokabatana alburnus n. sp. was erected for the parasite in topmouth culter.

Light microscopic study of four plagiorchiid trematodes infecting marine fish in the south-eastern Mediterranean Sea, Alexandria City, with descriptions of two new species

During the present investigation, a total of 220 fish specimens belonging to three different species, namely, little tunny Euthynnus alletteratus, African snook Lates niloticus, and striped red mullet Mullus surmuletus, were collected from January-November 2016 from the coasts off Abu Qir landing site, Alexandria City, south-eastern Mediterranean Sea, Egypt. The collected fish samples were dissected and examined for the presence of helminth parasites. Twenty-three out of 220 (10.45%) fish specimens were found to be naturally infected with four species of trematode parasites belonging to three different families of the order Plagiorchiida. The recovered parasite species were collected and identified by applying light microscopic examinations. The present study recorded two new parasite species, namely, Stephanostomum alletterani sp. nov. and Bathycreadium mulli sp. nov., belonging to the families Acanthocolpidae and Opecoelidae and infecting E. alletteratus and M. surmuletus, respectively and re-descriptions of the two remaining species, namely, Acanthostomum spiniceps and Aponurus mulli of the families Acanthostomatidae and Opecoelidae, respectively, to clarify the measurements of some body parts. Morphological and morphometric characterizations revealed some differences between the present species and other related species detected previously. Future studies are recommended to include advanced molecular characteristics for these species.

Microsporidians xenomas of anglerfish from NE Atlantic waters

The presence of emergent visible parasites at commercial valuable fish species is increasingly causing problems at fisheries and seafood industries. Microsporidians have been previously reported to appear forming apparent xenomas complexes in anglerfish species, but no effort has been carried out to simultaneously integrate epidemiological data, phenotypic, genotypic and fine structural characterizations in the same parasite sample. In this work, specimens of Lophius budegassa and Lophius piscatorius from NE Atlantic waters were sampled and examined to provide information about specific site of infection and demographic data of two groups of different sizes of xenomas present at both fish species. Histological descriptions and scanning and transmission electron microscopy were carried out on fresh spores of Lophius budegassa for ultrastructural studies. In both types of xenomas, it was observed simultaneously the microsporidian genus Spraguea in the form of two different types of spores. Molecular analyses of both xenomas from the two fish species, based on the small subunit ribosomal DNA gene, were also performed to genetically support the morphological diagnostic provided.

Morphological characterization and HSP70-, IGS-based phylogenetic analysis of two microsporidian parasites isolated from Antheraea pernyi

Two microsporidian isolates were extracted from single infected egg-laying tussah silk moth (Antheraea pernyi) in Liaoning Province, China. The microsporidia were subsequently grown in silk moth larvae, isolated, and subjected to morphological characterization (by light and transmission electron microscopy) and phylogenetic analysis (based on conserved genes). One type of spore was long-axis-oval in shape, measuring 4.71 × 1.95 μm, and the other type was short-axis-oval, measuring 3.64 × 2.17 μm. These dimensions were markedly different from those reported in the spores of the common microsporidia infecting A. pernyi, namely, Nosema pernyi (4.36 × 1.49 μm). A neighbor-joining phylogenetic tree based on HSP70 indicated that these microsporidia belonged to Nosema species and were closely related with Nosema bombycis and Nosema ceranae. Furthermore, in the phylogenetic tree based on the intergenic spacer (IGS) region, the long-axis-oval isolates were closely related and tended to form a clade away from the short-axis-oval isolates and N. pernyi isolates. The microsporidia isolated from A. pernyi clustered in one group. Nosema bombycis, Nosema spodopterae, and Endoreticulatus spp. appeared to be genetically distant from N. pernyi. The two isolates from A. pernyi fell in the Nosema group, but their spores differed from those of the spores of the common A. pernyi parasite N. pernyi, both in morphological and genetic aspects. The two isolates were designated Nosema sp. Ap (L) and Nosema sp. Ap (S). IGS was found to be informative in ascertaining phylogenetic relationships among species, and even closely related strains, of microsporidia.

Glugea jazanensis sp. nov. infecting Lutjanus bohar in the Red Sea: ultrastructure and phylogeny

During a survey of the microsporean fauna of the two-spot red snapper Lutjanus bohar Forsskål, 1775, from the Red Sea off Jizan (Saudi Arabia), a species of Glugea Thélohan, 1891 was found that did not conform to any known species. The species is characterized by the presence of spherical xenomas (ca. 2-5 mm in diameter) in the host body cavity. Examination of the lifecycle stages and mature spores using light and transmission electron microscopy also revealed morphological characteristics typical of species of the genus Glugea. Spores were elongated-ovoid with a posterior vacuole surrounded by the polar filament coils. Mature spores were 4.5 (4.0-4.8) µm long and 2.5 (2.0-2.5) µm wide. The polar filament was isofilar with 28 to 30 coils, although in most cases 29 coils, organized in 3 rows. Phylogenetic study based on the partial sequence of the small subunit (SSU) rRNA gene clustered the new microsporidia within the clade grouping species of the genus Glugea. The comprehensive analysis of the parasite's ultrastructural characteristics, together with molecular data for the SSU rDNA gene, suggests that this parasite is a new species of the genus Glugea, for which the name Glugea jazanensis sp. nov. is proposed.

Potaspora aequidens n. sp. (Microsporidia, Tetramicridae), a parasite infecting the freshwater fish Aequidens plagiozonatus (Teleostei, Cichlidae) from Brazil

Morphological and molecular procedures were used to describe a new species of microsporidian that infects the muscles of the sub-opercular region and the caudal fins of the freshwater Aequidens plagiozonatus in Brazil. This microsporidian forms whitish xenomas containing variable number of spores, reaching up to ~0.4 mm in diameter. The mature spores, pyriformin shape, with slightly round ends, measured 3.4 ± 0.5 μm long and 1.9 ± 0.3 μm wide (n = 50) and showed characteristics typical of Microsporidia. The average thickness of the spore wall was 100 (96-108) nm (n = 50), and the spore wall was composed of two layers, a thin, electron-dense exospore and a thick electron-transparent endospore. The exospore was surrounded by a thin, irregular layer of granular material. The anchoring disc was mushroom-like, located in the apical region of the spore in an eccentric position relative to the spore axis, rendering bilateral asymmetry to the spore. The anterior part of the polar filament (PF) (manubrium) measured approximately 125 (122-128) nm thick (n = 30), and the angle of tilt between the anterior PF and the spore axis was ~45°; the posterior part was packed in 8-9 coils. Phylogenetic analysis showed a strongly supported clade containing family Spragueidae Weissenberg, 1976, family Tetramicridae Matthews and Matthews, 1980, Microsporidium sp. RBS1, and Kabatana spp. In conclusion, the available morphological, ultrastructural, and molecular data shows that this microsporidian is a new species belonging to group 4, classified as Potaspora aequidens n. sp. This is the second species described in the genus Potaspora.

Morphological and phylogenetic analysis of Nosema sp. HR (Microsporidia, Nosematidae): a new microsporidian pathogen of Histia rhodope Cramer (Lepidoptera, Zygaenidae)

A new microsporidium was isolated from Histia rhodope Cramer (Lepidoptera, Zygaenidae), a pest of Bischofia javanica BL. in China. The morphology and molecular systematic of this novel microsporidian isolate had been described in this study. The spores were long oval and measured 3.1 × 1.9 μm on fresh smears. Ultrastructure of the spores was characteristic for the genus Nosema: 14-15 polar filament coils, posterior vacuole, and a diplokaryon. The sequenced rRNA gene of this isolate is 4309 bp long. The organization of the rRNA gene is 5'-LSU rRNA-ITS-SSU rRNA-IGS-5S-3', which is similar to that of other Nosema species (such as Nosema bombycis). Phylogenetic analysis based on LSU rRNA gene and SSU rRNA gene both revealed that this novel micorsporidian which isolated from H. rhodope had close relationship to the genus Nosema. Additionally, this isolate can also cause systemic infection of Bombyx mori. So, we should pay attention not only to N. bombycis, but also to other microsporidian (such as Nosema sp. HR) in sericulture in the future.

An original simple technique for diagnosis of Microsporidia using glycerol jelly direct smear

Microsporidia spp. are obligate intracellular parasites which are very minute with sizes ranging from 1 to 10 μm. They have been increasingly recognized as human pathogens in AIDS and immunocompromised patients, mainly associated with life-threatening chronic diarrhea and systemic disease. For accurate identification of Microsporidia, permanent staining techniques are used to enable the examiner to use the ×100 objective which reveals the important details needed for diagnosis. On the other hand, ×10 and ×40 objectives are of no value in detection of such a minute organism. Until now, there is no study that demonstrates a rapid satisfactory technique for routine examination of wet mount by the oil-immersion lens. Glycerol jelly (GJ) reagent was previously studied for its benefit in fixing the cover slide of direct wet mounts instantly enabling the use of oil-immersion lens in examination that magnifies its role as a rapid technique for direct examination. The aim of this research is to identify Microsporidia by wet mounts immediately, using GJ reagent that enables the examiner to use the ×100 objective and to evaluate GJ wet mount as a method of identification. Glycerol jelly reagent was prepared (7 g gelatin dissolved in 50 ml boiling water was added to 10 ml glycerol) and added to fecal wet mounts stained by iodine and methylene blue. Wet mounts were examined using the ×100 objective. Satisfactory results were achieved in spite of the small size of Microsporidia, as both iodine and methylene blue stained the cytological structures; GJ reagent fixed the cover slide, maintained the high translucency of the films, and enabled the examiner to use the ×100 oil-immersion objective. We also compared fecal wet mounts stained by iodine and methylene blue + GJ with a stool sample stained by permanent stain modified Ziehl-Neelsen without GJ, and we found that fecal wet mounts stained by iodine and methylene blue + GJ were more clear. We concluded that glycerol jelly wet mount is an easy, fast, reliable, and cheap technique for identification of Microsporidia in direct smear, using the ×100 oil-immersion objective.

Characterization of active ribosomal RNA harboring MITEs insertion in microsporidian Nosema bombycis genome

Microsporidia are a group of obligate intracellular parasites of medical and agricultural importance, which can infect almost all animals, including human beings. Using the genome data of Nosema bombycis, four families of miniature inverted-repeat transposable elements (MITEs) in ribosomal DNA (rDNA) were characterized in the microsporidian N. bombycis and were named LSUME1, ITSME1, SSUME1, and SSUME2, respectively. The genome-wide investigation of these MITEs shows that these MITEs families distribute randomly in N. bombycis genome. All insertion sequences have conserved characteristics of MITEs, the direct repeat sequence and terminal inverted-repeat sequence at both ends of each MITEs sequence. Additionally, using the CLC RNA Workbench Software, secondary structures of rRNA containing MITEs sequence have been predicted and were located in variable region or expansion segment. Furthermore, using two different probes, one is prepared by MITE sequence only (short probe) and the other is prepared by MITE sequence flanking partial rDNA sequence (long probe); northern blotting and dot blotting have been performed to detect the transcriptional and functional activity of the rDNA containing MITEs insertion. Fortunately, we found that the rDNA, which harbors the MITE, not only can be transcripted but also can form a complete ribosome. This is an interesting thing that one gene can keep active even when it has been inserted with another sequence. But the biological and structural significance of this observation is not readily apparent.

Morphological and ultrastructural description of Pleistophora dammami sp. n. infecting the intestinal wall of Saurida undosquamis from the Arabian Gulf, Saudi Arabia

Pleistophora dammami sp. n. is described from Saurida undosquamis from the Arabian Gulf in Saudi Arabia. Infection appeared as whitish cysts in the intestinal wall. Cysts ranged in size from 1 to 4 mm. The prevalence of the infection across both fish sexes was 17.5% (24/420). Two kinds of spores were recognized, microspores and macrospores, and each were ovoid in shape. The microspores measured ~2.5 × 2.0 μm in size, while the macrospores measured ~6.0 × 3.0 μm. Ultrastructurally, the parasite did not form xenoma but it formed cysts surrounded by thick cyst wall. All stages of development as meronts, sporonts, sporoblast and spores occurred in the cytoplasm of the host cells within sporophorous vesicles. The stages of development occurred asynchronously and thus all stages were randomly distributed within the cysts. Meronts were elliptical and multinucleated, with unpaired nuclei which constantly divided giving rise to new sporonts. During the transition to sporonts, the border of the meronts increased in thickness to form dense discontinuous cell coat. Later, the sporont divided into sporoblast cells which gradually differentiated the typical organelles of the spores. In mature spores, the polar filament was arranged in 20-24 coils in two rows either side of the posterior vacuole. All ultrastructural and morphological criteria indicate that the described species belongs to the genus Pleistophora.