Abstract:SUMMARY
Eukaryotic picoplankton was isolated from Lake Kinneret, Israel. This green picoplankton is spheroidal or ovoidal in shape. The cell wall has a network of ribs on its surface. The chloroplast is cup‐ or mantel‐shaped without a pyrenoid. The morphology and cellular structure of this autosporic alga is identical with Mychonastes homosphaera (Skuja) Kalina et Punčochářová. The phylogenetic tree based on 18S ribo‐somal RNA gene sequence data showed that M. homosphaera is placed in the Chlorophyceae and loc… Show more
“…The majority of the isolates were identified as members of the genus Choricystis (Somogyi et al 2016), which is widely distributed in freshwater lakes in Europe, Asia and North-America (Belykh et al 2000;Fawley et al 2004;Hepperle and Krienitz 2001;Hepperle and Schlegel 2002). Members of the Mychonastes clade, which were also isolated from Lake Balaton, are also reported from various lakes worldwide (Hepperle and Krienitz 2001;Hepperle and Schlegel 2002;Krienitz et al 1999;Fawley et al 2004;Hanagata et al 1999;Shi et al 2019).…”
Section: Diversity Of Eukaryotic Picoalgae In Lake Balatonmentioning
Occurrence of the smallest phototrophic microorganisms (photoautotrophic picoplankton, APP) in Lake Balaton was discovered in the early 1980s. This triggered a series of systematic studies on APP and resulted in the setting of a unique long-term picoplankton dataset. In this review, we intend to summarize the obtained results and to give a new insight on APP ecology and diversity in Lake Balaton. According to the results, APP dynamics depends on trophic state, temperature, nutrient, and light availability, as well as grazing pressure. APP abundance in Lake Balaton decreased to a low level (1-2 × 10 5 cells mL −1) as a consequence of decreasing nutrient supply (oligotrophication) during the past more than two decades, and followed a characteristic seasonal dynamics with higher abundance values from spring to autumn than in winter. Concomitantly, however, the APP contribution to both phytoplankton biomass and primary production increased (up to 70% and 40-50%, respectively) during oligotrophication. Regarding annual pattern, picocyanobacteria are dominant from spring to autumn, while in winter, picoeukaryotes are the most abundant, most likely due to the different light and temperature optima of these groups. Within picocyanobacteria, single cells and microcolonies were both observed with midsummer dominance of the latter which correlated well with the density of cladocerans. Community-level chromatic adaptation (i.e., dominance of phycoerythrin-or phycocyanin-rich forms) of planktonic picocyanobacteria was also found as a function of underwater light quality. Sequence analysis studies of APP in Lake Balaton revealed that both picocyanobacteria and picoeukaryotes represent a diverse and dynamic community consisting several freshwater genotypes
“…The majority of the isolates were identified as members of the genus Choricystis (Somogyi et al 2016), which is widely distributed in freshwater lakes in Europe, Asia and North-America (Belykh et al 2000;Fawley et al 2004;Hepperle and Krienitz 2001;Hepperle and Schlegel 2002). Members of the Mychonastes clade, which were also isolated from Lake Balaton, are also reported from various lakes worldwide (Hepperle and Krienitz 2001;Hepperle and Schlegel 2002;Krienitz et al 1999;Fawley et al 2004;Hanagata et al 1999;Shi et al 2019).…”
Section: Diversity Of Eukaryotic Picoalgae In Lake Balatonmentioning
Occurrence of the smallest phototrophic microorganisms (photoautotrophic picoplankton, APP) in Lake Balaton was discovered in the early 1980s. This triggered a series of systematic studies on APP and resulted in the setting of a unique long-term picoplankton dataset. In this review, we intend to summarize the obtained results and to give a new insight on APP ecology and diversity in Lake Balaton. According to the results, APP dynamics depends on trophic state, temperature, nutrient, and light availability, as well as grazing pressure. APP abundance in Lake Balaton decreased to a low level (1-2 × 10 5 cells mL −1) as a consequence of decreasing nutrient supply (oligotrophication) during the past more than two decades, and followed a characteristic seasonal dynamics with higher abundance values from spring to autumn than in winter. Concomitantly, however, the APP contribution to both phytoplankton biomass and primary production increased (up to 70% and 40-50%, respectively) during oligotrophication. Regarding annual pattern, picocyanobacteria are dominant from spring to autumn, while in winter, picoeukaryotes are the most abundant, most likely due to the different light and temperature optima of these groups. Within picocyanobacteria, single cells and microcolonies were both observed with midsummer dominance of the latter which correlated well with the density of cladocerans. Community-level chromatic adaptation (i.e., dominance of phycoerythrin-or phycocyanin-rich forms) of planktonic picocyanobacteria was also found as a function of underwater light quality. Sequence analysis studies of APP in Lake Balaton revealed that both picocyanobacteria and picoeukaryotes represent a diverse and dynamic community consisting several freshwater genotypes
“…The genus is currently represented by 20 species in Algaebase (Guiry & Guiry 2020); their characteristics and habitat preferences are described in Supplementary table. Species of this genus were previously found in Scotland, Germany, Slovakia, Russia, Ukraine, Brazil, Peru, Kenya, Angola, India, USA (Simpson & Valkenburg 1978;Hindák 1978;Komárek & Fott 1983;Hindák 1984;Hindák 1988a, b;Andreyeva 1998;Hanagata et al 1999;Tsarenko et al 2011;Krienitz et al 2011;Ramos et al 2015, etc).…”
This paper describes a new species from the Class Chlorophyceae, Mychonastes frigidus sp. nov., isolated from a cold-water mountain stream in the north of Russia (Subpolar Ural). The taxon is described using morphological and molecular methods. Mychonastes frigidus sp. nov. belongs to the group of species of the genus Mychonastes with spherical single cells. Comparison of ITS2 rDNA sequences and its secondary structures combined with the compensatory base changes approach confirms the separation between Mychonastes frigidus sp. nov and other species of the genus. Mychonastes frigidus sp. nov. represents a cryptic species that can only be reliably identified using molecular data.
“…In the tree, M.homosphaera was clustered by family, forming a monophyletic group with the other Mychonastaceae species. There was robust support (BP = 95) for the inclusion of M.homosphaera in Mychonastaceae , where it was positioned closest to Mychonastes homosphaera (AB025423) isolated from Lake Kinneret, Israel [ 19 ]. Fig.…”
Background: Picophytoplankton are abundant and can contribute greatly to primary production in eutrophic lakes. Mychonastes species are among the common eukaryotic picophytoplankton in eutrophic lakes. We used thirdgeneration sequencing technology to sequence the whole genome of Mychonastes homosphaera isolated from Lake Chaohu, a eutrophic freshwater lake in China. Result: The 24.23 Mbp nuclear genome of M.homosphaera, harboring 6649 protein-coding genes, is more compact than the genomes of the closely related Sphaeropleales species. This genome streamlining may be caused by a reduction in gene family number, intergenic size and introns. The genome sequence of M.homosphaera reveals the strategies adopted by this organism for environmental adaptation in the eutrophic lake. Analysis of cultures and the protein complement highlight the metabolic flexibility of M.homosphaera, the genome of which encodes genes involved in light harvesting, carbohydrate metabolism, and nitrogen and microelement metabolism, many of which form functional gene clusters. Reconstruction of the bioenergetic metabolic pathways of M.homosphaera, such as the lipid, starch and isoprenoid pathways, reveals characteristics that make this species suitable for biofuel production. Conclusion: The analysis of the whole genome of M. homosphaera provides insights into the genome streamlining, the high lipid yield, the environmental adaptation and phytoplankton evolution.
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