Protist最新文献

Although copper (Cu²⁺) is a micronutrient, the metal may be toxic if present in high concentrations in soil ecosystems and subsequently affect various organisms, ranging from microorganisms to earthworms. We performed a microcosm study with an array of Cu²⁺ concentrations, with a specific focus on Cercozoa, an important protozoan group in most soil food webs. Research on Cercozoa is still scarce in terms of both diversity and ecology; hence, to explore this group in more depth, we used high-throughput sequencing to detect Cu²⁺ induced community changes. Increased levels of Cu²⁺ caused a shift in the cercozoan community, and we observed decreased cercozoan relative abundance across the majority of orders, families and genera. Due to their key role in soil food webs, especially as bacterial predators and providers of nutrients to plants, the reduction of cercozoan abundance and diversity may seriously affect soil functionality. Our results indicate that the increase of Cu²⁺ concentrations in the soil could potentially have this effect and the consequences need exploration.

The present investigation focused on studying the phylogenetic position of the green Noctiluca endosymbiont, Pedinomonas noctilucae, collected from the Gulf of Mannar, India. In this study, we re-examined the evolutionary position of this endosymbiotic algae using rbcL sequences. The phylogenetic analysis revealed that P. noctilucae is distantly related to the Pedinomonas species, and formed a monophyletic clade with Marsupiomandaceae. Based on the phylogenetic association of endosymbiont with Maruspiomonadales it was concluded that the endosymbiont belongs to an independent genus within the family Marsupiomonadaceae. At the site of the bloom, Noctiluca scintillans was found to exhibit a dense monospecific proliferation, with an average cell density of 27.l88 × 10³ cells L⁻¹. The investigation revealed that the green Noctiluca during its senescent phase primarily relied on autotrophic nutrition, which was confirmed by the presence of a high number of trophonts, vegetatively reproducing cells (1.45 × 10³ cells L⁻¹) and the absence of food vacuoles.

Herein we describe a new photosynthetic euglenoid species found in Poland - Euglena mazurica. A large population exists in a small, eutrophic body of water located in a pasture near Mikołajki town inside the Masurian Landscape Park (covering a part of the Masurian Lake District in Poland). The unique cell shape (corkscrew-like) discerns it well from other previously described euglenoid species with metabolic cells. The new species possesses two plate-like chloroplasts each with a pyrenoid accompanied by two paramylon caps placed on either side of it (diplopyrenoids). On the phylogenetic tree, the new species is situated within the Euglena clade. Though it is a sister branch to three clades – one representing the similar Euglena agilis, characterized by its fusiform cells and two chloroplasts with diplopyrenoids, the two species are clearly morphologically and molecularly distinct.

Biological complexity is challenging to define, but can be considered through one or more features, including overall genome size, number of genes, morphological features, multicellularity, number of life cycle stages and the ability to adapt to different environments. Euglena gracilis meets several of these criteria, with a large genome of ∼38,000 protein coding genes and a considerable ability to survive under many different conditions, some of which can be described as challenging or harsh. Potential molecular exemplars of complexity tying these aspects together are signalling pathways, including GTPases, kinases and ubiquitylation, which increase the functionality of the gene-encoded proteome manyfold. Each of these examples can modulate both protein activity and gene expression. To address the connection between genome size and complexity I have undertaken a brief, and somewhat qualitative, survey of the small ras-like GTPase superfamily of E. gracilis. Unexpectedly, apart from Rab-GTPases which control intracellular transport and organelle identify, the size of the GTPase cohort is modest, and, for example, has not scaled with gene number when compared to the close relatives, trypanosomatids. I suggest that understanding the functions of this protein family will be vital to uncovering the complexity of E. gracilis biology.

Though endosymbioses between protists and prokaryotes are widespread, certain host lineages have received disproportionate attention what may indicate either a predisposition to such interactions or limited studies on certain protist groups due to lack of cultures. The euglenids represent one such group in spite of microscopic observations showing intracellular bacteria in some strains. Here, we perform a comprehensive molecular analysis of a previously identified endosymbiont in the Eutreptiella sp. CCMP3347 using a single cell approach and bulk culture sequencing. The genome reconstruction of this endosymbiont allowed the description of a new endosymbiont Candidatus Grellia alia sp. nov. from the family Midichloriaceae. Comparative genomics revealed a remarkably complete conjugative type IV secretion system present in three copies on the plasmid sequences of the studied endosymbiont, a feature missing in the closely related Grellia incantans. This study addresses the challenge of limited host cultures with endosymbionts by showing that the genomes of endosymbionts reconstructed from single host cells have the completeness and contiguity that matches or exceeds those coming from bulk cultures. This paves the way for further studies of endosymbionts in euglenids and other protist groups. The research also provides the opportunity to study the diversity of endosymbionts in natural populations.

The morphology, morphogenesis, and molecular phylogeny of Heterometopus palaeformis (Kahl, 1927) Foissner, 2016 were studied using microscopical observations on live and protargol-stained specimens as well SSU rRNA gene sequencing. The morphogenetic data for the genus are presented for the first time. Compared to other metopids, the morphogenesis of H. palaeformis is distinct since its (1) perizonal stripe rows 4 and 5 are involved in the formation of the opisthe’s adoral polykinetids; (2) perizonal stripe rows 3–5 and two adjacent preoral dome kineties contribute to most of the opisthe’s paroral membrane while perizonal stripe rows 1 and 2 contribute very little; (3) four kinety rows are formed to the left of the opisthe’s adoral zone of polykinetids. The Chinese population resembles the original and neotype populations well in terms of general morphology — characterized by a life size of 55–120 × 10–20 μm, an elongate ellipsoidal body with a hardly spiralized flat preoral dome, about 18 somatic kineties and 20 adoral polykinetids. The SSU rDNA sequence of the present population exhibits a disparity of 1.33%–2.22% divergence from sequences of other populations. Nevertheless, phylogenetic analysis reveals that populations of H. palaeformis form a separate, stable cluster within the paraphyletic Metopidae clade.

Algicidal bacteria exhibit promising potential against harmful algal blooms (HABs); however, their application has been limited due to their limited algicidal activity. This study demonstrates the enhanced algicidal activity of Alteromonas sp. FDHY-CJ bacteria against harmful Skeletonema costatum using a 5 L fermenter. Utilizing this refined framework increased the OD₆₀₀ value and algal cell mortality by 6.50 and 2.88 times, respectively, compared to non-optimized culture cultivated in a flask using marine broth 2216E medium. The mechanism of action involves significant inhibition of algal photosynthetic efficiency with concurrent degradation of photosynthetic pigments. Relative to the non-optimized group, the optimized bacterial treatment led to a significant increase in H₂O₂ and MDA (malondialdehyde) by 19.54 and 4.22-fold, respectively, and resulted in membrane damage. The culture optimization procedure yielded effectual algicidal substances capable of considerably reducing the severity of S. costatum HABs through cell membrane disruption.

Multiple genes encoding family A DNA polymerases (famA DNAPs), which are evolutionary relatives of DNA polymerase I (PolI) in bacteria and phages, have been found in eukaryotic genomes, and many of these proteins are used mainly in organelles. Among members of the phylum Euglenozoa, distinct types of famA DNAP, PolIA, PolIBCD+, POP, and eugPolA, have been found. It is intriguing how the suite of famA DNAPs had been established during the evolution of Euglenozoa, but the DNAP data have not been sampled from the taxa that sufficiently represent the diversity of this phylum. In particular, little sequence data were available for basal branching species in Euglenozoa until recently. Thanks to the single-cell transcriptome data from symbiontids and phagotrophic euglenids, we have an opportunity to cover the “hole” in the repertory of famA DNAPs in the deep branches in Euglenozoa. The current study identified 16 new famA DNAP sequences in the transcriptome data from 33 phagotrophic euglenids and two symbiontids, respectively. Based on the new famA DNAP sequences, the updated diversity and evolution of famA DNAPs in Euglenozoa are discussed.

Euglena gracilis, photosynthetic protist, has a unique ability to generate wax esters in the absence of oxygen, employing a distinctive fatty acid synthesis mechanism. Through comprehensive inhibitor assays and gene-silencing techniques, our research clearly emphasized the indispensable role of the mitochondrial anaerobic respiratory chain in this biosynthesis. We identified acyl-CoA dehydrogenase, electron transfer flavoprotein (ETF), and rhodoquinone (RQ) as central molecular components in the pathway. These findings strongly indicated a potential reversal of beta-oxidation occurring within mitochondria for fatty acid production in anaerobic conditions. Furthermore, our analysis revealed the pivotal function of nicotinamide nucleotide transhydrogenase (NNT) in efficiently managing the NADPH/NAD⁺ conversion essential for sustaining anaerobic metabolism. This review outlines our key findings and provides a comprehensive understanding of the molecular mechanisms that enable E. gracilis to produce wax ester anaerobically.