Protist最新文献

Stentor pyriformis is a unicellular organism whose inherent green-algal symbionts can be utilized in evolutionary and cytological studies. The cytoplasm contains symbiotic algae and starch granules, which are in constant motion. The habitats of the ciliate S. pyriformis are restricted to a few oligotrophic ponds in Japan. This study aimed to develop a culture medium for long-term incubation based on pond water quality data and to investigate the cytoplasmic streaming of symbiotic algae and starch granules in S. pyriformis. In addition, the involvement of the cytoskeleton and motor proteins in cytoplasmic streaming was examined using microtubule polymerization and dynein ATPase inhibitors. The results indicated that the cytoplasmic streaming in S. pyriformis is associated with the microtubule system. Immunofluorescence and transmission electron microscopy revealed the presence of KM-fibers, bundles of microtubules running longitudinally along the cell surface. These findings suggest a possible link between microtubules and cytoplasmic streaming in S. pyriformis.

Choanoflagellate species have been taxonomically divided upon the morphological and developmental basis of their extracellular coat (periplast). Species within the order Craspedida possess a purely organic periplast, whereas taxa of the order Acanthoecida have an additional silica based periplast termed the lorica. Whilst small-scale phylogenetic studies have recovered the two orders as monophyletic, recent phylogenomic analyses have rejected the monophyly of the craspedids. These analyses suggest that the freshwater craspedid Codosiga hollandica falls within the earliest branching choanoflagellate lineage; however, it has also been noted that phylogenomic studies result in inconsistent phylogenies, with unstable long-branched species being recovered as basal choanoflagellates. Presented here are phylogenetic analyses, based upon slowly evolving ribosomal proteins, which consistently recover both craspedid monophyly and a derived placement of C. hollandica. The addition of further, long-branched, ribosomal proteins to phylogenetic analyses are shown to generate longer terminal branches and a weakening of the support for Craspedida. The analyses highlight the requirement for an increase in data, in terms of both taxa and gene coverage, to successfully resolve the earliest craspedid branches. In addition, phylogenetically unstable species are identified that are recommended to be omitted from phylogenomic studies as they have the potential to disrupt recovered relationships.

This study discovered the first Asian population of Sphaeroforma nootkatensis (SphX), a member of Mesomycetozoea, in the southern coastal region of South Korea. Although investigating parasites in Pacific oysters (Crassostrea gigas), a single-cell microorganism was isolated from gill tissues. Comprehensive phylogenetic analysis of its 18S rDNA revealed its placement within the order Ichthyophonida, class Mesomycetozoea. SphX formed a distinct cluster within Sphaeroforma spp., separate from Pseudoperkinsus tapetis. Morphological examinations of in vitro cultured cells revealed two distinctive life stages characterized by multilobe and granular sporangium, accompanied by corresponding non-motile larger and motile smaller endospores, respectively. Scanning electron microscope analysis depicted lobular and smooth surfaces on vegetative cells, indicative of differing life cycle stages. Transmission electron microscope observations revealed intriguing features consistent with previous reports on Mesomycetozoea. A prominent fibrillar structure was noted in a vegetative cell. In contrast, smaller endospores were observed with cilia-like structures surrounding the cell wall, indicating their mode of movement. The Ray's fluid thioglycollate medium assay showed that SphX cells were digested, whereas some small endospores remained resistant. This discovery provides novel insights into the life stages of Mesomycetozoans and geographical distribution and underscores the importance of monitoring oyster health for effective aquaculture management.

Reclamation of petroleum-polluted environments is a key issue for today and in the future, as our reliance on oil will persist for decades. An eco-friendly solution is to use microbes that play a role in petroleum-hydrocarbon degradation. However, as hydrocarbon degradation involves a multi-step process involving different functional groups, focusing only on finding efficient bacterial species will not be the complete solution. Heterotrophic protists are unicellular eukaryotic microorganisms that could play a role in remediation of ecosystems by enhancing petroleum-hydrocarbon degradation through different mechanisms. This mini-review discusses the importance of protists in the degradation of petroleum-hydrocarbon and their predatory impact on hydrocarbon-degrading bacterial communities. Additionally, the effect of hydrocarbons on protistan community structure and protistan cells is discussed. A better understanding of the puzzle hydrocarbon-protist interactions will significantly increase our knowledge of how to employ these microbes for bioremediation of hydrocarbon pollutants.

Morphology of seven chrysophycean stomatocysts was studied using scanning electron microscopy. All stomatocysts were recorded from the shallow lakes located in the Steppe zone of South Urals. Four morphotypes (stomatocyst 373 Taylor et Smol, stomatocyst 68 Van de Vijver et Beyens, stomatocyst 99 Pang et Wang and stomatocyst 101 Pang et Wang Forma B) are rare and reported for the first time in Russia. New observations on the formation of the cyst ornamentation allowed us to amend the descriptions of two morphotypes. Three stomatocysts are described as new to science. Morphological variability of all seven morphotypes are illustrated and discussed.

The morphology, morphogenesis, molecular phylogeny, and the resting cyst morphology of the freshwater ciliate, Crassohymena primicirrata (Berger and Foissner, 1987) n. gen., n. comb., found in samples collected from South Korea, were investigated. The Korean two populations observed are identical to each other and are highly similar to the type population showing only few and minor differences in the size and arrangement of cortical granules and the length of dorsal kinety 4. The new genus Crassohymena n. gen. is established and characterized by a number of morphological and ontogenetic features: the thick undulating membranes comprising three or four rows of kinetosomes and in Cyrtohymena pattern; the anteriorly distinctly displaced transverse cirri; the posteriorly set-off cirrus V/3; the opisthe's anlagen IV-VI originate from cirri IV/2, V/4, and V/3, respectively; the proter's anlagen IV-VI originate from cirrus IV/3; and the enormous anlage I in each daughter cell. Phylogenetic analyses based on 18S rRNA gene sequences show that Crassohymena primicirrata n. gen., n. comb. is separated from all other morphologically most similar taxa and forms an adelphotaxon to the clade containing sequences of the families Neokeronopsidae and Spirofilidae, and the two oxytrichid genera Australocirrus and Notohymena.