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The purpose of this study was to assess the efficacy of certain plant extracts and to compare them with current biocides on the viability of Acanthamoeba castellanii cysts and trophozoites in vitro. Amoebicidal and cysticidal assays were performed against both trophozoites and cysts of Acanthamoeba castellanii (ATCC 50370). Ten plant extracts were evaluated alongside the current agents included polyhexamethylene biguanide (PHMB), octenidine and chlorhexidine digluconate. A. castellanii (ATCC 50370) was treated to serial two-fold dilutions of the test compounds and extracts in microtitre plate wells to investigate the effect on trophozoites and cysts of A. castellanii (ATCC 50370). Furthermore, the toxicity of each of the test compounds and extracts were assessed towards a mammalian cell line. Minimum trophozoite inhibitory concentration (MTIC), minimum trophozoite amoebicidal concentration (MTAC), and minimum cysticidal concentration (MCC) were used to establish A. castellanii (ATCC 50370) in vitro sensitivity. The findings of this research revealed that the biguanides PHMB, chlorhexidine, and octenidine all had excellent effectiveness against trophozoites and cysts of A. castellanii (ATCC 50370). The plant extracts testing results showed that, great activity against trophozoites and cysts of A. castellanii (ATCC 50370) at lower concentrations. This is the first study to demonstrate that the Proskia plant extract had the lowest MCC value, which was 3.9 µg/mL. The time kill experiment confirmed this finding, as this extract reduced cysts of A. castellanii (ATCC 50370) by more than 3-log at 6 hour and by 4-log after 24 hour. The anti-amoebic efficacy of new plant extracts on the viability of A. castellanii (ATCC 50370) cysts and trophozoites was comparable to existing biocide treatments and was not toxic when tested on a mammalian cell line. This could be a promising novel Acanthamoeba treatment by using the tested plant extracts as a monotherapy against trophozoites and cysts.

Microalgal conversion of high-level CO₂ in industrial flue gas to value-added products is attractive technology for mitigating global warming. However, reduction of microalgal production costs for medium ingredients, particularly nitrogen salts, is essential. The use of atmospheric nitrogen as a nitrogen source for microalgal cultivation will dramatically reduce its production costs. We attempted to enrich a microalga–bacteria community, which fixes both CO₂ and atmospheric nitrogen under high level CO₂. By cultivating biofilm recovered from the surface of cobbles in a riverbank, a microalgal flora which grows in a nitrogen salts-free medium under 10% CO₂ was enriched, and the coccoid microalgal strain MP5 was isolated from it. Phylogenetic analysis revealed that the strain MP5 belongs to the genus Coelastrella, and the closest known species was C. terrestris. With PCR–DGGE analysis, it was found that the enriched microalgal community includes bacteria, some of which are suggested diazotrophs. The addition of bactericides in culture medium inhibited MP5 growth, even though the strain MP5 is eukaryotic. Growth of bacteria-free MP5 was stimulated by addition of Agrobacterium sp. isolates in nitrogen salts-free medium, suggesting that MP5 and the bacteria have responsibility for photosynthetic carbon fixation and nitrogen fixation, respectively.

Gertia stigmatica is a recently described member of the Kareniaceae with a peridinin-containing plastid rather than the aberrant, haptophyte-derived, tertiary plastid found in canonical Kareniaceae genera such as Karenia, Karlodinium, and Takayama. G. stigmatica provides a unique opportunity to compare biochemical traits, such as sterol composition, between these two fundamentally different types of Kareniaceae. To this point, canonical members of the Kareniaceae have been observed to typically produce a set of 4α-methyl-substituted, Δ⁸⁽¹⁴⁾-nuclear-unsaturated major sterols, such as (24R)-4α-methyl-5α-ergosta-8(14),22-dien-3β-ol (gymnodinosterol) and 27-nor-(24R)-4α-methyl-5α-ergosta-8(14),22-dien-3β-ol (brevesterol), which are very uncommon throughout other members of the class Dinophyceae. Our objective was to compare the sterols of G. stigmatica to canonical Kareniaceae to elucidate whether these same distinctive sterols are found, with our hypothesis being that they would because G. stigmatica is indeed a member of the Kareniaceae. Contrary to our hypothesis, G. stigmatica lacks gymnodinosterol and brevesterol, with its sterols instead dominated by 4-desmethyl sterols, such as cholesterol, 24-methylcholesta-5,22E-dien-3β-ol, and the unusual tri-unsaturated sterols ergosta-5,8(14),22E-trien-3β-ol and cholesta-5,8(14),22E-trien-3β-ol. No sterols were found to possess a 4α-methyl substituent or a single Δ⁸⁽¹⁴⁾ nuclear unsaturation. Thus, G. stigmatica's sterol composition as a member of the Kareniaceae is atypical.

There are several alveolate groups outside the well-studied trio – ciliates, dinoflagellates, and apicomplexans – that are crucial for understanding the evolution of this major taxon. One such assemblage is the “colponemids”, which are eukaryotrophic biflagellates, usually with a ventral groove associated with the posterior flagellum. Previous phylogenetic studies show colponemids forming up to three distinct deep branches within alveolates (e.g. sister groups to Myzozoa or all other alveolates). We have developed dieukaryotic (predator–prey) cultures of four colponemid isolates. One represents the first stable culture of the halophile Palustrimonas (feeding on Pharyngomonas), while SSU rDNA phylogenies show the other isolates as two distinct new lineages. Neocolponema saponarium gen. et sp. nov. is a swimming alkaliphile with a large groove, which feeds on a kinetoplastid. Loeffela hirca gen. et sp. nov. is halophilic, has a subtle groove, usually moves along surfaces, and feeds on Pharyngomonas and Percolomonas. Prey capture in both new genera is raptorial, involves a specialized structure/region to the right of the proximal posterior flagellum, and presumed extrusomes. The relationships amongst Myzozoa, ciliates, and the (now) five described colponemid clades are unresolved, signaling that colponemid diversity represents both a challenge and important resource for tracing deep alveolate evolution.

Blastocystis is one of the most common intestinal protists in humans and a great number of animals, including sheep and goats. High prevalence and multiple subtypes of Blastocystis have been reported in sheep in several regions of China and elsewhere. However, there is a dearth of knowledge about Blastocystis in Tibetan sheep. A total of 761 fecal samples were collected from Tibetan sheep in seven counties of Qinghai Province, northwestern China, and were examined for the prevalence and subtypes of Blastocystis using molecular technology based on the partial small subunit ribosomal RNA gene of Blastocystis. The overall prevalence of Blastocystis in the investigated Tibetan sheep was 7.5% (57/761) using PCR and DNA Sanger sequencing, and differences in prevalence were observed among the ruminants from the seven counties (P < 0.01), and across four seasons (P < 0.01). Sequence analysis revealed five subtypes (ST14 (57.9%), ST10 (26.3%), ST12 (5.3%), ST21 (5.3%), and ST30 (5.3%)) of Blastocystis sp. in these Tibetan sheep, with ST14 as the predominant subtype. To our knowledge, this is the first report of Blastocystis colonization in Tibetan sheep.

Bioassays using cultures of the toxic haptophyte Prymnesium parvum and the ciliate Cyclidium sp. as prey were conducted to test the effect of pH (range = 6.5 – 8.5), salinity (range = 1.50 – 7.50‰), and a combination of pH and salinity on the toxicity of P. parvum. pH had a significant effect on P. parvum toxicity. Toxicity was rapidly (within 24 hr) induced by increasing pH of the medium, or reduced by lowering pH. Conversely, lowering salinity reduced toxicity, albeit less effectively compared to pH, and P. parvum cells remained toxic at the lowest values tested (1.50‰ at pH 7.5). An additional effect between pH and salinity was also observed: low salinity combined with low pH led to not only decreased toxicity, but also resulted in lower P. parvum growth rates. Such effects of pH and salinity on P. parvum growth and toxicity provide insight into the environmental factors supporting community dominance and toxic blooms of the alga.

Biological soil crusts (BSC) are associations of different macro and microorganisms and aggregated soil particles located on the surface of soils in many different habitats. BSC harbour a diverse and complex community of ciliates and testate amoebae. These phagotrophic protists play an important role in C and N recycling in soil ecosystems but have not been frequently studied in BSC. In this context, the effects of three increasing N inputs on ciliates and testate amoebae in crusts from a semi-arid Mediterranean ecosystem were evaluated. A field experiment with artificial N-deposition was designed to mimic the effects caused by anthropogenic N depositions. The results have shown that the protist populations of these semi-arid Mediterranean environments have lower species richness than other soil environments. The increase in N produces a net loss of diversity in the populations studied and shifts in the community structure. It has also been shown that some ciliates and testate amoebae, due to their population responses to increased N concentrations, could potentially be used as bio-indicators of N contamination in these BSCs.

Meltwater runoff from glaciers carries particles, so-called glacial flour that may affect planktonic organisms and the functioning of marine ecosystems. Protist microplankton is at the base of marine food webs and thus plays an important role in sustaining important ecosystem services. To assess the effect of glacial flour on photoautotrophic, heterotrophic and mixotrophic microplankton, the spatial distribution of these trophic groups was studied in four Greenlandic fjords during summer. The results suggest that the abundance of the autotrophic microplankton was affected by the glacier meltwater due to reduced light penetration and nutrient availability. The abundance of heterotrophic and mixotrophic microplankton were not apparently affected by the glacier meltwater. Incubation experiments were conducted on the natural population and in laboratory cultures of two mixoplanktonic ciliate species. The experiments on the natural population revealed that none of the trophic groups were affected by the suspended material at concentrations up to 50 mg L⁻¹. The experiments on cultures gave no indication that glacial flour was ingested by the mixoplanktonic ciliates. Growth rates of cultured ciliates were not affected by the glacial flour addition. These results suggest that heterotrophic and mixotrophic microplankton are not affected by glacial flour as much as autotrophic microplankton.