28 research outputs found
Protist community composition in the Pacific sector of the Southern Ocean during austral summer 2010
Knowledge about the protist diversity of the
Pacific sector of the Southern Ocean is scarce. We tested
the hypothesis that distinct protist community assemblages
characterize large-scale water masses. Therefore, we
determined the composition and biogeography of late
summer protist assemblages along a transect from the coast
of New Zealand to the eastern Ross Sea. We used state of
the art molecular approaches, such as automated ribosomal
intergenic spacer analysis and 454-pyrosequencing, combined
with high-performance liquid chromatography pigment
analysis to study the protist assemblage. We found
distinct biogeographic patterns defined by the environmental
conditions in the particular region. Different water
masses harbored different microbial communities. In contrast
to the Arctic Ocean, picoeukaryotes had minor
importance throughout the investigated transect and
showed very low contribution south of the Polar Front.
Dinoflagellates, Syndiniales, and small stramenopiles were
dominating the sequence assemblage in the Subantarctic
Zone, whereas the relative abundance of diatoms increased
southwards, in the Polar Frontal Zone and Antarctic Zone.
South of the Polar Front, most sequences belonged to haptophytes.
This study delivers a comprehensive and taxon
detailed overview of the protist composition in the investigated
area during the austral summer 2010
Picoeukaryote Plankton Composition off West Spitsbergen at the Entrance to the Arctic Ocean
Investigation of marine eukaryotic picoplankton composition is limited by missing morphological features for appropriate identification. Consequently, molecular methods are required. In this study, we used 454-pyrosequencing to study picoplankton communities at four stations in the West Spitsbergen Current (WSC; Fram Strait). High abundances of Micromonas pusilla were detected in the station situated closest to Spitsbergen, as seen in surveys of picoplankton assemblages in the Beaufort Sea. At the other three stations, other phylotypes, affiliating with Phaeocystis pouchetii and Syndiniales in the phylogenetic tree, were present in high numbers, dominating most of them. The picoplankton community structures at three of the stations, all with similar salinity and temperature, were alike. At the fourth station, the influence of the East Spitsbergen Current, transporting cold water from the Barents Sea around Spitsbergen, causes different abiotic parameters that result in a significantly different picoeukaryote community composition, which is dominated by M. pusilla. This observation is particularly interesting with regard to ongoing environmental changes in the Arctic. Ongoing warming of the WSC could convey a new picoplankton assemblage into the Arctic Ocean, which may come to affect the dominance of M. pusilla
The genome sequence of Pycnococcus provasolii (CCAP190/2) (Guillard, 1991) [version 1; peer review: 2 approved]
We present a genome assembly from cultured Pycnococcus provasolii (a marine green alga; Chlorophyta; None; Pseudoscourfieldiales; Pycnococcaceae). The genome sequence is 32.2 megabases in span. Most of the assembly is scaffolded into 44 chromosomal pseudomolecules (99.67%). The mitochondrial and plastid genomes have also been assembled, and the length of the mitochondrial scaffold is 24.3 kilobases and of the plastid genome has been assembled and is 80.2 kilobases in length
Chytrid fungi distribution and co-occurrence with diatoms correlate with sea ice melt in the Arctic
Global warming is rapidly altering physicochemical attributes of Arctic waters. These changes are predicted to alter microbial networks, potentially perturbing wider community functions including parasite infections and saprotrophic recycling of biogeochemical compounds. Specifically, the interaction between autotrophic phytoplankton and heterotrophic fungi e.g. chytrids (fungi with swimming tails) requires further analysis. Here, we investigate the diversity and distribution patterns of fungi in relation to abiotic variables during one record sea ice minimum in 2012 and explore co-occurrence of chytrids with diatoms, key primary producers in these changing environments. We show that chytrid fungi are primarily encountered at sites influenced by sea ice melt. Furthermore, chytrid representation positively correlates with sea ice-associated diatoms such as Fragilariopsis or Nitzschia. Our findings identify a potential future scenario where chytrid representation within these communities increases as a consequence of ice retreat, further altering community structure through perturbation of parasitic or saprotrophic interaction network
A diversified and segregated mRNA spliced-leader system in the parasitic Perkinsozoa
Spliced-leader trans-splicing (SLTS) has been described in distantly related eukaryotes and acts to mark mRNAs with a short 5′ exon, giving different mRNAs identical 5′ sequence-signatures. The function of these systems is obscure. Perkinsozoa encompasses a diversity of parasitic protists that infect bivalves, toxic-tide dinoflagellates, fish and frog tadpoles. Here, we report considerable sequence variation in the SLTS-system across the Perkinsozoa and find that multiple variant SLTS-systems are encoded in parallel in the ecologically important Perkinsozoa parasite Parvilucifera sinerae. These results demonstrate that the transcriptome of P. sinerae is segregated based on the addition of different spliced-leader (SL) exons. This segregation marks different gene categories, suggesting that SL-segregation relates to functional differentiation of the transcriptome. By contrast, both sets of gene categories are present in the single SL-transcript type sampled from Maranthos, implying that the SL-segregation of the Parvilucifera transcriptome is a recent evolutionary innovation. Furthermore, we show that the SLTS-system marks a subsection of the transcriptome with increased mRNA abundance and includes genes that encode the spliceosome system necessary for SLTS-function. Collectively, these data provide a picture of how the SLTS-systems can vary within a major evolutionary group and identify how additional transcriptional-complexity can be achieved through SL-segregation
Regional variability in eukaryotic protist communities in the Amundsen Sea
We determined the composition and structure of late summer eukaryotic protist assemblages
along a west–east transect in the Amundsen Sea. We used state-of-the-art molecular approaches, such as
automated ribosomal intergenic spacer analysis (ARISA) and 454-pyrosequencing, combined with pigment
measurements via high performance liquid chromatography (HPLC) to study the protist assemblage. We
found characteristic offshore and inshore communities. In general, total chlorophyll a and microeukaryotic
contribution were higher in inshore samples. Diatoms were the dominant group across the entire area, of
which Eucampia sp. and Pseudo-nitzschia sp. were dominant inshore and Chaetoceros sp. was dominant
offshore. At the most eastern station, the assemblage was dominated by Phaeocystis sp. Under the ice,
ciliates showed their highest and haptophytes their lowest abundance. This study delivers a taxon detailed
overview of the eukaryotic protist composition in the Amundsen Sea during the summer 2010
Identification of a non-canonical ciliate nuclear genetic code where UAA and UAG code for different amino acids.
The genetic code is one of the most highly conserved features across life. Only a few lineages have deviated from the "universal" genetic code. Amongst the few variants of the genetic code reported to date, the codons UAA and UAG virtually always have the same translation, suggesting that their evolution is coupled. Here, we report the genome and transcriptome sequencing of a novel uncultured ciliate, belonging to the Oligohymenophorea class, where the translation of the UAA and UAG stop codons have changed to specify different amino acids. Genomic and transcriptomic analyses revealed that UAA has been reassigned to encode lysine, while UAG has been reassigned to encode glutamic acid. We identified multiple suppressor tRNA genes with anticodons complementary to the reassigned codons. We show that the retained UGA stop codon is enriched in the 3'UTR immediately downstream of the coding region of genes, suggesting that there is functional drive to maintain tandem stop codons. Using a phylogenomics approach, we reconstructed the ciliate phylogeny and mapped genetic code changes, highlighting the remarkable number of independent genetic code changes within the Ciliophora group of protists. According to our knowledge, this is the first report of a genetic code variant where UAA and UAG encode different amino acids
Example multiple sequence alignments of <i>Plagiopyla frontata</i> genes with internal UGA codons identified by PhyloFisher with orthologous sequences spanning Eukaryota.
Example multiple sequence alignments of Plagiopyla frontata genes with internal UGA codons identified by PhyloFisher with orthologous sequences spanning Eukaryota.</p
Bayesian phylogenomic analysis of 46 ciliate species and 9 outgroup Alveolata species, based on a concatenated alignment of 89 BUSCO proteins under the CAT-GTR model using PhyloBayes-MPI.
Bayesian phylogenomic analysis of 46 ciliate species and 9 outgroup Alveolata species, based on a concatenated alignment of 89 BUSCO proteins under the CAT-GTR model using PhyloBayes-MPI.</p