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50 results for “18S rDNA”
18S V4 rDNA sequences organized at the OTU level for the SOMLIT-Astan time-series (2009-2016)
<p>The present file includes metadata for each 18S V4<strong> rDNA OTU</strong> from the SOMLIT-Astan time series (2009-2016) including the following fields: <strong>amplicon</strong> = identifier of the representative (most abundant) sequence; <strong>total</strong> = total number of reads; <strong>spread </strong>= number of samples in which the OTU has been found; <strong>cloud </strong>= number of unique sequences constituting the OTU; <strong>sequence</strong> = nucleic acid sequence of the representative sequence; <strong>length</strong> = length of the representative sequence; <strong>quality </strong>= minimum expected error observed for the representative sequence, divided by sequence length; <strong> taxonomy</strong> = taxonomic path assigned to the representative sequence; <strong>identity</strong> = percentage of identity of the representative sequence to the closest reference sequence from PR2; <strong>references</strong> = best hit reference sequence(s) ; <strong>RA090107_02:RA161222_3 </strong>= 375 samples from January 2009 to December 2016, the first two number are the year followed by the month and the day (sampling twice a month during 8 years). Values after “_” indicate the size of the filter used for the filtration: 02 for 0.2 µm and 3 for 3 µm.</p> <p>Generation of 18S V4 rDNA Operational Taxonomic Units (OTUs) from the raw sequencing reads and their assembly into a OTUtable was obtained according to the following pipeline (https://doi.org/10.5281/zenodo.5791089). The V4 region was extracted from the 18S rDNA reference sequences from PR2 v4.12 (Guillou et al., 2013) with Cutadapt. The representative sequences of each OTU were compared to these V4 reference sequences by pairwise global alignment (usearch_global VSEARCH’s command). Each OTU inherits the taxonomy of the best hit or the last common ancestor in case of ties. OTUs with a score below 80% similarity were considered as unassigned (Mahé et al., 2017; Stoeck et al., 2010).</p> <p>The final dataset (filtered OTU table) contains 375 samples (sampled twice per month from 2009 to 2016) with a total of ~30 million sequence reads and 21,418 OTUs.</p>
EukRibo: a manually curated eukaryotic 18S rDNA reference database
<p>EukRibo is a manually curated database of reference small-subunit ribosomal RNA gene (18S rDNA) sequences of eukaryotes, specifically aimed at taxonomic annotation of high-throughput metabarcoding datasets. Unlike other reference databases of ribosomal genes, it is not meant to exhaustively capture all publicly available 18S rDNA sequences from the INSDC repositories, but to represent a subset of highly trustable sequences covering the whole known diversity of eukaryotes, with a focus on protists, manually verified taxonomic identifications, and relatively low genetic redundancy.</p> <p>EukRibo is part of a suite of public resources generated by the UniEuk project (www.unieuk.org), which are all designed to follow a common taxonomic framework for maximal interoperability. The high level of taxonomic accuracy of EukRibo, together with a newly designed, phylogenetically-informed annotation approach, allow high confidence in the taxonomic annotation of environmental metabarcodes, as well as identification of new eukaryotic diversity at various taxonomic levels using a connected components approach.</p> <p>* * *</p> <p>Accompanying preprint available at <a href="https://doi.org/10.1101/2022.11.03.515105">https://doi.org/10.1101/2022.11.03.515105</a>.</p> <p>* * *</p> <p><strong>EukRibo ReadMe file, versions 1 and 2</strong></p> <p>Each EukRibo release consists of <strong>4 files</strong>:<br> - a <strong>tsv table </strong>containing the taxonomic and other information about the 18S rDNA sequences included in the release<br> - a <strong>fasta file </strong>containing the <strong>full sequences </strong>as retrieved from the INSDC repositories (NCBI, EMBL-EBI/ENA, DDBJ)<br> - a <strong>fasta file </strong>containing the <strong>variable region V4 </strong>extracted from all these sequences (based on the fragment amplified with the Tara-Oceans V4 primers)<br> - a <strong>fasta file </strong>containing the <strong>variable region V9 </strong>extracted from the subset of sequences where it is present (based on the fragment amplified with the Tara-Oceans V9 primers)</p> <p>The primary goal of EukRibo was to be used to annotate the EukBank meta-dataset of available V4 metabarcoding datasets, and therefore all sequences included in EukRibo contain the variable region V4.<br> Only a subset of these sequences (about 75%) also contain the variable region V9; this is because many 18S rDNA sequences in the INSDC repositories stop before the V9 fragment.</p> <p>Sequences with slightly incomplete V4 or V9 fragments were kept if phylogenetically useful - i.e. if they are the only available representatives of a certain taxonomic lineage.<br> <strong>V4 </strong>We allowed up to 50 missing positions in the relatively conserved area at the 5' end of the V4 fragment (for an average fragment length of about 380 bp); no sequence incomplete at the 3' end of the V4 fragment is included.<br> <strong>V9 </strong>We allowed up to 30 missing positions in the relatively conserved area at the 3' end of the V9 fragment (for an average length of about 135 bp); no sequence incomplete at the 5' end of the V9 fragment is included.<br> We allowed a higher proportion of missing positions for the V9 region because being more conservative would imply losing too many sequences, including entire taxonomic lineages.</p> <p><strong>Version 1 of EukRibo</strong><br> This is the starting version of EukRibo that was used for the taxonomic annotation of the EukBank dataset, with taxonomy strings that were fixed as of October 2020.<br> - Contains 46,345 sequences with a sufficiently complete V4 region; 46,299 with the actual complete V4 region and 46 (about 0.1%) with missing positions at the 5' end.<br> - Of these, 34,438 also include a sufficiently complete V9 region; 23,226 with the actual complete V9 region and 11,206 (about 33%) with missing positions at the 3' end.</p> <p><strong>Version 2 of EukRibo</strong><br> This is a version of EukRibo that was made taxonomically compatible with version 3 of the EukProt database (<a href="https://doi.org/10.1101/2020.06.30.180687">https://doi.org/10.1101/2020.06.30.180687</a>), with taxonomic revisions as of July 2022 as well as additional information on the included selection of sequences that was not provided in the tsv file of version 1.<br> - Contains the exact same selection of sequences as in version 1, with the addition of genus <em>Meteora</em>, the last remaining known supergroup-level eukaryotic lineage for which an 18S rDNA was not previously available. (The <em>Meteora </em>sequence contains the full V4 fragment but does not include a sufficiently complete V9 fragment.)<br> - Only 34,432 sequences with a sufficiently complete V9 region are now retained because of 6 previously unrecognised chimeric sequences where the V9 fragment does not originate from the same organism as the V4 fragment.</p> <p><strong>Files in EukRibo version 1</strong>:<br> 46345_EukRibo.tsv.gz<br> 46345_EukRibo_full_seqs.fas.gz<br> 46345_EukRibo_V4.fas.gz<br> 34438_EukRibo_V9.fas.gz</p> <p>The tsv file contains 6 columns:<br> <strong>gb_accession </strong>- INSDC accession number of the sequence<br> <strong>supergroup</strong>, <strong>taxogroup1</strong>, <strong>taxogroup2 </strong>- binning of the taxa into strictly monophyletic clades of evolutionary and/or ecological significance<br> <strong>UniEuk_taxonomy_string </strong>- full UniEuk-compatible taxonomic annotation of the sequence<br> - an unlimited number of levels is allowed (going down to strain for isolated organisms or to clone for environmental sequences)<br> - informal names are used for phylogenetically supported clades without formal name<br> <strong>V9 </strong>- presence ('Y') or absence ('N') of a sufficiently complete V9 fragment in the sequence</p> <p><strong>Files in EukRibo version 2</strong>:<br> 46346_EukRibo-02.tsv.gz<br> 46346_EukRibo-02_full_seqs.fas.gz<br> 46346_EukRibo-02_V4.fas.gz<br> 34432_EukRibo-02_V9.fas.gz</p> <p>The tsv file now contains 12 columns:<br> <strong>gb_accession</strong>, <strong>supergroup</strong>, <strong>taxogroup1</strong>, <strong>taxogroup2</strong>, <strong>UniEuk_taxonomy_string</strong><br> - same columns as in version 1<br> <strong>alternative_strain_names </strong>(new) - provides alternative strain/isolate names when known to help cross-linking genetic data coming from the same organism<br> <strong>V4 </strong>(new) - indicates whether the V4 fragment is complete ('yes - complete') or missing positions at the 5' end ('yes - partial')<br> <strong>V9 </strong>(emended content) - now contains more precise information than in version 1 about whether it is complete ('yes - complete'), missing positions at the 3' end ('yes - partial'), or was excluded, and the 6 possible reasons why ('no - missing', 'no - too incomplete', 'no - chimera', 'no - bad quality', 'no - deletion in V9', 'no - Ns in V9')<br> <strong>EukProt_ID_same_strain </strong>(new) - accession of EukProt datasets from the same isolate<br> <strong>EukProt_ID_different_strain </strong>(new) - accession of EukProt datasets from a different isolate of the same species<br> <strong>columns_modified_since_previous_version </strong>(new) - lists all of the 6 pre-existing columns that have a modified content compared to version 1<br> <strong>remarks </strong>(new) - additional information such as presence of an intron in the V9 fragment, taxonomic identity of the two parts of chimeric sequences, or the presence of Ns or a deletion in the V4 or the V9 fragment (but insufficient to warrant exclusion)</p>
rDNA 18S V9 metabarcoding tables (Swarm) for Tara Oceans Expedition (2009-2013), including Tara Polar Circle Expedition (2013)
<p>Reads were grouped into OTUs using the following swarm-based pipeline: paired-end reads were merged with vsearch’s --fastq_mergepairs command (version 2.15.1, allowing for staggered reads; Rognes et al., 2016), and trimmed with cutadapt (version 3.0; Martin, 2011), keeping only reads containing both forward and reverse primers. After trimming, the expected error per read was estimated with vsearch’s command --fastq_filter and the option --eeout. Each sample was then de-replicated, i.e. strictly identical reads were merged, using vsearch’s command --derep_fulllength, and converted into fasta format. Clustering was performed at the sample level with swarm 3.0 using default parameters (Mahé et al., 2015). Prior to global clustering, individual fasta files (one per sample) were pooled and further dereplicated with vsearch. Files containing per-read expected error values were also dereplicated to retain only the lowest expected error for each unique sequence. Global clustering was performed with swarm (using the fastidious option). Cluster representative sequences were then searched for chimeras with vsearch’s command --uchime_denovo using default parameters (Edgar et al., 2011).</p> <p>Clustering results, expected error values, taxonomic assignments, and chimera detection results were used to build a “raw” occurrence table. Reads without primers, reads shorter than 32 nucleotides and reads with uncalled bases (“N”) were discarded. For a “filtered” occurrence table, non-chimeric sequences, sequences with an expected error per nucleotide below 0.0002, and clusters containing at least 2 reads were retained. Since primer trimming is not perfect, some sequences can still contain primer fragments or be excessively trimmed. These sub- or super-sequences were identified using vsearch and merged with their closest, most abundant perfectly trimmed sequence. Finally, occurrence patterns throughout our sample collection were used to further refine the occurrence table. Clusters that contain sub-clusters with only a single-nucleotide difference but with different ecological patterns (defined here as uncorrelated abundance values in at least 5% of the samples) were turned into distinct clusters (https://github.com/frederic-mahe/fred-metabarcoding-pipeline). On the other hand, clusters with similar sequences that had correlated abundance values in at least 95% of the samples, were merged using a re-implementation of lulu's method (Frøslev et al. 2017; https://github.com/frederic-mahe/mumu).</p> <p> </p>
Fig. 5. Phylogenetic relationships between jellyfishes within the order Semaeostomeae inferred from nearly complete 18S in Comprehensive Analysis of the Jellyfish (Goette, 1886) (Semaeostomeae: Pelagiidae) with Description of the Complete rDNA Sequence.
Fig. 5. Phylogenetic relationships between jellyfishes within the order Semaeostomeae inferred from nearly complete 18S rDNA (A) and partial 28S rDNA sequences (B) with maximum-likelihood (ML) algorithms. ML analyses of 18S and 28S were used as the nucleotide substitution model of GTR+G. Two hydrozoans (Hydractinia echinata and Podocoryne carnea for 18S rDNA; Astrohydra japonica and Melicertissa sp. for 28S) were included as the outgroups. Additional Bayesian analysis generated similar topology of the tree compared with the ML tree. Posterior probabilities (PP) from the analyses were incorporated into the ML tree to support the strength of each branch. The first and second numbers at the nodes display bootstrap proportions (BP) (> 50%) in ML and PP (> 0.50) in Bayesian, respectively. Branch lengths are proportional to the scale given. *Represents controversial species names, because they were suspected as different species by Bayha et al. (2017).
Fig. 4 in The distribution and host-association of a haemoparasite of damselfishes (Pomacentridae) from the eastern Caribbean based on a combination of morphology and 18S rDNA sequences
Fig. 4. Phylogenetic analysis of the Haemohormidium-like parasite based on 18S rDNA sequences. Bayesian inference (BI) analysis showing the phylogenetic relationships for 8 Haemohormidium-like parasite isolates, 6 from the present study (GenBank: MH401637-42) (in bold) and 2 from Renoux et al. (2017), isolated from three species of Stegastes including Stegastes adustus, Stegastes diencaeus and Stegastes planifrons, from 5 sites in the eastern Caribbean. Comparative sequences representing known coccidia, with Adelina dimidiata (DQ096835) as outgroup, were downloaded from the GenBank database. Nodal support values> 50% are represented on the tree.
Fig. 2 in The distribution and host-association of a haemoparasite of damselfishes (Pomacentridae) from the eastern Caribbean based on a combination of morphology and 18S rDNA sequences
Fig. 2. Peripheral blood stages of the Haemohormidium-like parasite infecting species of Stegastes. Giemsa stained light micrographs of the Haemohormidium-like parasite as observed in the peripheral blood of Stegastes diencaeus from St Thomas, eastern Caribbean (Genbank accession number MH401641). A. rare possible trophozoite stage. B. possible meront stages undergoing transverse binary fission. C. possible meront stages undergoing longitudinal binary fission. Scale bar = 10 μm.
Fig. 3 in The distribution and host-association of a haemoparasite of damselfishes (Pomacentridae) from the eastern Caribbean based on a combination of morphology and 18S rDNA sequences
Fig. 3. Prevalence of infection differences among six Stegastes spp., averaged across six study sites. 95% confidence intervals calculated using the Wilson procedure with continuity corrections. Different lower-case letters above each bar indicates a significant (p ≤ 0.05) difference between species, as indicated by a binomial logistic regression (GLMM results shown in Table 1).
Fig. 1 in The distribution and host-association of a haemoparasite of damselfishes (Pomacentridae) from the eastern Caribbean based on a combination of morphology and 18S rDNA sequences
Fig. 1. Map of the Eastern Caribbean region showing collection sites for the current study and Cook et al., 2015.
Fig. 5 in Description of Sarcocystis scandentiborneensis sp. nov. from treeshrews (Tupaia minor, T. tana) in northern Borneo with annotations on the utility of COI and 18S rDNA sequences for species delineation
Fig. 5. Phylogenetic tree based on analysis of mitochondrial COI sequences of the Sarcocystidae including the new Sarcocystis sp. examined in this study (black symbols). Other taxa of the Apicomplexa served as root. Evolutionary history was inferred by the Maximum Likelihood (ML) method based on the TamuraNei model, whereby 619 positions were included in the final data set. All positions with less than 95% site coverage were eliminated; that is, fewer than 5% alignment gaps, missing data, and ambiguous bases were allowed at any position. Bootstrap percentages (1000 iterations) are shown next to branches. COI sequences E357-13 and E120-13 (not shown in the tree) are available at GenBank (MN732561 and MN732562, respectively).
Fig. 2 in Description of Sarcocystis scandentiborneensis sp. nov. from treeshrews (Tupaia minor, T. tana) in northern Borneo with annotations on the utility of COI and 18S rDNA sequences for species delineation
Fig. 2. Ultrastructure of S. scandentiborneensis sp. nov. Note, due to ethanol-fixation some ultrastructural details are poorly resolved (e.g. membranes). A) Longitudinal section through the same sample as in Fig. 1C, showing a gross view of the sarcocyst and its villous protrusions (VP) that are sectioned in different orientations. The inset shows a cross section through various VP that reveals the arrangement of microtubules in their inner core; while in this case 16 microtubules are visible (asterisks), sections through more apical portions of the VP showed lower numbers. B) Longitudinal section through the fingerlike VPs that appear to be anchored in the ground substance (arrow) by microtubules (asterisks) that extend into each protrusion; note the electron-dense, U-shaped structure at each tip of the protrusions (arrowheads) and the apparently serrated surface of the VP (flat arrowheads). The inset shows a higher magnification of the apical part of a single VP with the typical U-shaped apex (asterisk), which appears to be connected with the host cell through an electronlucent contact zone (white arrowheads); interestingly, the protrusion appears fenestrated (also visible in the main image) possessing thorn-like structures (black arrows; the white arrow indicates a crosssectional view) that could be responsible for the serration visible at lower magnification. CZ, cystozoites; HC, host cell; VP, villous protrusion.
Fig. 1 in Description of Sarcocystis scandentiborneensis sp. nov. from treeshrews (Tupaia minor, T. tana) in northern Borneo with annotations on the utility of COI and 18S rDNA sequences for species delineation
Fig. 1. Light microscopy of Sarcocystis scandentiborneensis sp. nov. A and B, Haematoxylin & Eosinstained histological sections of striated musculature; C and D, Richardson's dye-stained 1.0 μm thin sections of sarcocysts. A) Tissue section of laryngeal muscle with various sarcocysts in cross section (asterisks), indicating a relatively high density of cysts in this part of musculature. B) Longitudinal section through a sarcocyst, showing a cigar-shaped appearance; however, isolated native sarcocysts, which were not available, may look different. C) Part of a longitudinal section through the tip of a sarcocyst, note the very thin ground substance (arrows) and the fine septae extending into the interior of the cyst (arrowheads); cystozoites (CZ) were loosely scattered within chambers while metrocytes were rarely seen, indicating maturity of the cyst; bars indicate the variable thickness of the cyst wall: the wall was thinner in regions where the villous protrusions were bent (right bar); note that the intense staining at the interface between host cell (HC) and parasite is part of the host cell. D) Cross-section through a sarcocyst showing cystozoites and the cyst wall (bar) including its thin ground substance (arrows).
Fig. 4 in Description of Sarcocystis scandentiborneensis sp. nov. from treeshrews (Tupaia minor, T. tana) in northern Borneo with annotations on the utility of COI and 18S rDNA sequences for species delineation
Fig. 4. Mapping (to the Toxoplasma gondii reference molecule M97703) of frequencies (%) of base pair changes observed in sequence comparisons of nu clear 18S rDNA within the new Sarcocystis sp. from treeshrews (intraspecific variation: isolates E364–13 versus E357–13) and between the new species and Sarcocystis zuoi and/or S. clethrionomyelaphis (interspecific variation: E364–13 versus S. zuoi/clethrionomyelaphis). Results were combined for the two latter species to simplify the graph. Here, 87.2% of 2118 alignment positions showed moderate to high levels of consistency, while sections of ambiguous alignment did not relate to the species under investigation. Due to gaps in the alignment, not all of the observed nt changes could be mapped to a homologous position of the reference molecule (i.e., 7 out of 24 bp changes in intraspecific comparison; 33 out of 74 bp changes in interspecific comparison), in which case the position of each nt relative to the helix was inferred from neighboring nt for which such position was known. Gaps were mainly due to insertions in helices V2, V4, and V9 rendering E357-13/E364-13 longer than the sequence of T. gondii. The percentage of parsimony-informative (pi) bp changes per helix is shown for helices V1, V2, V4, V7, and V9 above each column. Also shown is the ratio of transitions versus transversions (Ti/Tv) for selected helices.
Fig. 5. A data-display network constructed from uncorrected 18S rDNA p in Toxoplasma gondii and related Sarcocystidae parasites in harvested caribou from Nunavik, Canada
Fig. 5. A data-display network constructed from uncorrected 18S rDNA p-distances, using all characters, for tissue dwelling coccidians (mostly Sarcocystis spp.). Group names bear no taxonomic designation but merely assigned for discussion purposes. Bootstrap supports are displayed by the gray curves and associated values imposed on the network. Red dots indicate sequences generated in this study. (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.)
Figure 5 in Combined-data phylogenetics and character evolution of Clitellata (Annelida) using 18S rDNA and morphology
Figure 5. Phylogenetic tree obtained from one of the three replicate Bayesian inference runs of the combined (18S rDNA, somatic, and spermatozoal) data set. Posterior probabilities ± 0.85 are indicated in front of the nodes.
Figure 4 in Combined-data phylogenetics and character evolution of Clitellata (Annelida) using 18S rDNA and morphology
Figure 4. Parsimony consensus tree of the combined (18S rDNA, somatic, and spermatozoal) data set. Bootstrap frequencies ± 50% are indicated above the branches.
Figure 2 in Combined-data phylogenetics and character evolution of Clitellata (Annelida) using 18S rDNA and morphology
Figure 2. Phylogenetic tree obtained from one of the three replicate Bayesian inference runs of the 18S rDNA sequences. Posterior probabilities ± 0.85 are indicated in front of the nodes.
Figure 1 in Combined-data phylogenetics and character evolution of Clitellata (Annelida) using 18S rDNA and morphology
Figure 1. Schematic representation of some of the 34 considered spermatozoal characters. Inset, hypothetical plesiomorphic spermatozoon for the Clitellata, as inferred from ancestral-state reconstruction analysis (modified from Jamieson et al., 1987).
Tara Oceans (2009-2013) rDNA 18S V9 ASV table (DADA2) with nf-core/ampliseq
<p>This repository contains datasets describing the DADA2 ASVs generated from <em>Tara</em> Oceans 18S V9 rDNA data. The ASVs were generated using the nf-core workflow <a href="https://nf-co.re/ampliseq" target="_blank" rel="noopener">ampliseq</a>. Please refer to the readme file (README.html) for more details.</p>
Tara Oceans (2009-2013) rDNA 18S V4 ASV table (DADA2) with nf-core/ampliseq
<p>This repository contains datasets describing the DADA2 ASVs generated from <em>Tara</em> Oceans 18S V4 rDNA data. The ASVs were generated using the nf-core workflow <a href="https://nf-co.re/ampliseq" target="_blank" rel="noopener">ampliseq</a>. Please refer to the readme file (README.html) for more details.</p>
Cryptosporidium Nested-PCR on 18S rDNA Tutorial
<p>Video tutorial for<em> Cryptosporidium</em> spp. identification by nested-PCR on 18S rDNA locus.</p>
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