Protist最新文献

Louis Joblot published one of the first manuals of microscopy in 1718, just a few years before both he and Leeuwenhoek died. It contained Joblot's microscope designs and his extensive observations on microorganisms including experiments on spontaneous generation. Joblot's work and his observations have often been overlooked, misdated, and denigrated. This is due to attention given to a few apparently fanciful drawings of microorganisms, and the identification of his work as appearing in a posthumous 1754 edition. The second edition not only placed Joblot's work as decades after Leeuwenhoek's death, but was also expanded by the publisher to include unattributed material from famous sources. Here an attempt is made to shine a light on Joblot's work and bring it out of Leeuwenhoek's shadow.

A new bakuellid ciliate, Holostichides eastensis nov. spec. isolated from China, is investigated in terms of its morphology, ontogenesis, and molecular phylogenesis. It is characterized by size 150–180 µm × 45–60 µm in vivo; 27–46 macronuclear nodules; cortical granules dark brown, spherical, about 0.5 µm across, clustered in groups and then arranged longitudinally; three frontal cirri with one to four smaller cirri below the middle one, a buccal cirrus, nine to 15 frontoterminal cirri, and midventral complex composed of five to eight cirral pairs and two long midventral rows. The main events during binary fission are as follows: (1) in the proter, the undulating membrane anlage is formed from both the dedifferentiation of old undulating membranes and the basal bodies developing de novo, and the proximal part of the parental adoral zone of membranelles is renewed by a field of basal bodies that originates de novo; (2) in the opisthe, the oral primordium is formed intrakinetally; (3) besides the middle frontal cirrus and buccal cirrus, the FVT-anlagen II produces the extra one to four cirri. Phylogenetic analyses based on SSU rDNA sequence data suggest a close relationship between Holostichides eastensis nov. spec. and its congeners, indicating that the genus Holostichides is monophyletic.

The genus Hyalosira Kützing was recently split and emended based on morphology and molecular phylogeny but many uniseriate taxa could not be resolved. All populations examined in that study had one rimoportula on each valve (i.e., 1 + 1 in the cell). Recent collections from Turkey, Australia, and Micronesia had uniseriate taxa with different numbers of rimoportulae and other new features distinguishing them from all other uniseriate taxa. Two species had two rimoportulae per valve (i.e., 2 + 2) and deep septa, of which one is shown to be Hyalosira hesperia Álvarez-Blanco & S.Blanco, for which we provide a revised description, and the other, from Melbourne and Yap, is proposed as H. pacifica, sp. nov. They are separated by stria density and copula areola density. A third species, from the Great Barrier Reef, H. flexa, sp. nov., is the first Hyalosira found with heterovalvy—including a rimoportula on only one valve (i.e., 1 + 0)—and heteropolarity, including three variously reduced pore fields and the fourth, with the rimoportula, always involved in attachment, essentially a basal pole. A corrected diagnosis of the genus is provided and implications for exploring the functions of rimoportulae are discussed.

Platyproteum is an enigmatic, monotypic genus formerly assigned to the Apicomplexa, until a recent phylogenomic study demonstrated that it diverged from the base of the chromerid/colpodellid (chrompodellid) taxa and apicomplexan clade. In the present study, a new species, P. noduliferae n. sp., is described using a combination of morphological and molecular data. Moreover, a reconstruction of the flagellar apparatus is presented to characterize the presence of flagella which was, until this study, an unknown trait for this genus. Phylogenetic analyses using rDNA sequences suggested that P. noduliferae n. sp. is a sister species of P. vivax, diverging from the base of chrompodellids and apicomplexans. This study provides new morphological data that corroborates the position of Platyproteum amongst other biflagellate species, contributing to an improved understanding of Platyproteum and the evolutionary changes undergone by some marine alveolates as they transitioned into obligate parasitic life styles.

Unicellular green biflagellates of the order Volvocales (Chlorophyceae, Chlorophyta) are common inhabitants of various types of habitats, and can also form peculiar interspecific relationships. Most of their morphological diversity has historically been assigned to the two prominent genera Chlamydomonas and Chloromonas. Ongoing reclassification of these algae, aided by molecular phylogenetics, has resulted in numerous newly proposed genera, but there are certainly brand-new taxa awaiting recognition. In this study, based on morphological and ultrastructural observations together with sequence data of the nuclear 18S and ITS2 rDNA and the plastid rbcL gene, we describe Adglutina synurophila gen. et sp. nov., a volvocalean biflagellate isolated from colonies of the golden-brown alga Synura petersenii (Chrysophyceae). Phylogenetic analyses placed Adglutina in the phylogroup Moewusinia as a sister lineage to the acidophilic “Chlamydomonas” species. It is characterised by having oval to broadly ellipsoidal cells with a low keel-shaped papilla and a cup-shaped chloroplast lacking a pyrenoid, but possessing a lateral eyespot of a variable position. The unique set of features, together with its Synura-loving nature, anchor Adglutina as a well distinguishable phylogenetic lineage within the Moewusinia. The novel alga has a widespread distribution; it has been found in three European countries to date.

The Class Nassophorea is not monophyletic with unsolved relationship of four orders, which calls for discussion to combine morphological features and molecular phylogeny. In the present study, the ultrastructure of Apocolpodidium etoschense in the order Colpodidiida is first studied. Comparisons between orders of Nassophorea were conducted and a discussion of systematics was performed based on a SSU rRNA gene-based phylogeny. The order Colpodidiida and Nassulida shared the following features: Two pairs of alveolocysts in the cortex, the presence of a ‘‘B-cartwheel’’ in the distal region of the kinetosome, the presence of cytostomal lamellae and subcytostomal lamellae in the cytopharyngeal basket, and spindle trichocysts with a simple tip. These similarities shape a core group of Nassophorea, which are morphologically and genetically different from the order Microthoracida. Consequently, Microthoracida should be regarded as an independent taxon rather than a member of Nassophorea. Within the core group of Nassophorea, Colpodidiida as an independent order is further validated by its delicate cytopharyngeal basket which lacks nematodesmal lamellae; while the non-monophyly of the order Nassulida might be explained by differentiation of the cartwheels in kinetosomes and the arrangement of kinetosomes with postciliary microtubules in the nassulid organelle 3 within its members.

To infect the human host, Entamoeba histolytica carries out processes requiring cytoskeleton remodeling, which involves reorganizing the actin fibers. However, little is known about the external influence factors, e.g., the pH, on the parasite's cytoskeleton remodeling or cell morphology. Such influence becomes relevant given the pH gradient that the amoeba cope with when going through the human colonic mucus during infection. Therefore, we analyzed the proliferation, the reorganization of the actin fibers, and other actin structures and cell shape during adhesion to fibronectin and erythrophagocytosis in trophozoites at different external pH conditions (6.0, 6.5, 6.8, 7.5, 8.0). We found that the best condition of external pH to perform such functions was 6.8. At acid pH, the trophozoites presented better-defined actin fibers that formed a more compact network, while at alkaline pH, the fibers reorganized, forming a looser and less defined network. Similarly, the number of actin dots also changed from acid to alkaline pH. In conclusion, the external pH alters the proliferation of the amoebas and promotes the dynamic restructuration of their cytoskeleton, allowing them to carry out their functions.

Diplonemids are a group of flagellate protists, that belong to the phylum Euglenozoa alongside euglenids, symbiontids and kinetoplastids. They primarily inhabit marine environments, though are also found in freshwater lakes. Diplonemids have been considered as rare and unimportant eukaryotes for over a century, with only a handful of species described until recently. However, thanks to their unprecedented diversity and abundance in the world oceans, diplonemids now attract increased attention. Recent improvements in isolation and cultivation have enabled characterization of several new genera, warranting a re-examination of all available knowledge gathered so far. Here we summarize available data on diplonemids, focusing on the recent advances in the fields of diversity, ecology, genomics, metabolism, and endosymbionts. We illustrate the life stages of cultivated genera, and summarise all reported interspecies associations, which in turn suggest lifestyles of predation and parasitism. This review also includes the latest classification of diplonemids, with a taxonomic revision of the genus Diplonema. Ongoing efforts to sequence various diplonemids suggest the presence of large and complex genomes, which correlate with the metabolic versatility observed in the model species Paradiplonema papillatum. Finally, we highlight its successful transformation into one of few genetically tractable marine protists.

Ciliated protozoa play important ecological roles in soils, yet few studies have investigated the effect of soil pollution on them. We determined the effect of copper (Cu) and cypermethrin on a soil ciliate community under microcosm conditions. Soils were treated with Cu or cypermethrin and the abundance and species richness of ciliates determined 15 days later. Cu treatment increased soil ciliates abundance at the highest concentration (960 mg kg⁻¹), as did cypermethrin at a treatment of 160 mg kg⁻¹. No negative effect on ciliate abundance was found for either substance due to increased numbers of tolerant species, particularly Homalogastra setosa and Chilodonella uncinata in the case of Cu and Colpoda stenii and Colpoda inflata for cypermethrin treatments. However, several species were absent at high treatment levels. Notably, Halteria grandinella was not found in Cu treatments above 240 mg kg⁻¹, whilst Oxytricha setigera was not found in cypermethrin treatments above 160 mg kg⁻¹. For Homalogastra setosa, there was an initial positive response to cypermethrin, but abundance then decreased at a treatment of 320 mg kg⁻¹, and treatment at 640 mg kg⁻¹ eradicated the species from the microcosms. Accordingly, both substances affected the structure of the soil ciliate community at high concentrations.