Dataset's files
| Action | DRS | |||
|---|---|---|---|---|
| ERR5210640_1.fastq.gz | Fastqsanger.gz | |||
| ERR5210640_2.fastq.gz | Fastqsanger.gz | |||
| ERR5210650_1.fastq.gz | Fastqsanger.gz | |||
| ERR5210650_2.fastq.gz | Fastqsanger.gz | |||
| ERR5210660_1.fastq.gz | Fastqsanger.gz |
Items per page: 5 1 - 5 of 128 |
Similar Datasets
Project description:Marine protist diversity in European coastal waters and sediments as revealed by high-throughput sequencing
| PRJEB9133 | ENA
Project description:IntroductionEquine theileriosis, an economically important disease that affects horses and other equids worldwide, is caused by a tick-borne intracellular apicomplexan protozoa Theileria equi. Genotyping of T. equi based on the 18S rRNA gene revealed the presence of two, three, four or five genotypes. In previous published reports, these genotypes have been labelled either alphabetically or numerically, and there is no uniformity in naming of these genotypes. The present study was aimed to revisit the phylogeny, genetic diversity and geographical distribution of T. equi based on the nucleotide sequences of the V4 hypervariable region of the 18S rRNA gene available in the nucleotide databases.MethodsOut of 14792 nucleotide sequences of T. equi available in the GenBank™, only 736 sequences of T. equi containing the complete V4 hypervariable region of the 18S rRNA gene (>207 bp) were used in multiple sequence alignment. Subsequently, a maximum likelihood phylogenetic tree was constructed based on the Kimura 2-parameter model (K2+I).ResultsThe phylogenetic tree placed all the sequences into four distinct clades with high bootstrap values which were designated as T. equi clades/ genotypes A, B, C and D. Our results indicated that the genotype B of Nagore et al. and genotype E of Qablan et al. together formed the clade B with a high bootstrap value (95%). Furthermore, all the genotypes probably originated from clade B, which was the most dominant genotype (52.85%) followed by clades A (27.58%), and C (9.78%) and D (9.78%). Genotype C manifested a comparatively higher genetic diversity (91.0-100% identity) followed by genotypes A (93.2-99.5%), and B and D (95.7-100%). The alignment report of the consensus nucleotide sequences of the V4 hypervariable region of the 18S rRNA gene of four T. equi genotypes (A-D) revealed significant variations in one region, between nucleotide positions 113-183, and 41 molecular signatures were recognized. As far as geographical distribution is concerned, genotypes A and C exhibited far-extending geographical distribution involving 31 and 13 countries of the Asian, African, European, North American and South American continents, respectively. On the contrary, the genotypes B and D exemplified limited distribution with confinement to 21 and 12 countries of Asian, African and European continents, respectively. Interestingly, genotypes A and C have been reported from only two continents, viz., North and South America. It was observed that genotypes A and C, and B and D exhibit similar geographical distribution.DiscussionThe present study indicated the presence of only four previously described T. equi genotypes (A, B, C and D) after performing the molecular analyses of all available sequences of the complete V4 hypervariable region of the 18S rRNA gene of T. equi isolates in the GenBank™.
| S-EPMC10978764 | biostudies-literature
Project description:Illumina sequencing is a representative tool for understanding the massive diversity of microbial eukaryotes in natural ecosystems. Here, we investigated the eukaryotic community in a pond (salinity of 2-4) on Dokdo (island) in the East Sea, Korea, using Illumina sequencing with primer sets for the V4 and V9 regions of 18S rDNA from 2016 to 2018 for the first time. Totally, 1,413 operational taxonomic units (OTUs) and 915 OTUs were detected using the V9 and V4 primer sets, respectively. Taxonomic analyses of these OTUs revealed that although the V4 primer set failed to describe the extant diversity for some major sub-division groups, the V9 primer set represented their diversity. Moreover, the rare taxa with <1% of total reads were exclusively detected using V9 primer set. Hence, the diversity of the eukaryotic community can vary depending on the choice of primers. The Illumina sequencing data of the V9 region of 18S rDNA may be advantageous for estimating the richness of the eukaryotic community including a rare biosphere, whereas the simultaneous application of two biomarkers may be suitable for understanding the molecular phylogenetic relationships. We strongly recommend both biomarkers be used to assess the diversity and phylogenetic relationship within the eukaryotic community in natural samples.
| S-EPMC7162856 | biostudies-literature
Project description:DNA barcoding is a molecular tool that exploits a unique DNA sequence of a standardized gene or non-coding region for the species identification of unknown individuals. The investigation into a suitable barcode for diatoms is ongoing and there are several promising candidates including mitochondrial, plastidial and nuclear markers. We analyzed 272 sequences from 76 diatoms species in the orders Thalassiosirales, Lithodesmiales and Cymatosirales, using distance and character based approaches, to assess the applicability of a DNA barcode based on the hypervariable V4 region of the nuclear 18S rRNA gene. We show that the proposed V4 barcode separated ca. 97% of all centric diatom taxa tested using a threshold p-distance of 0.02 and that many problem pairs were further separated using a character based approach. The reliability of amplification, extensive reference library and variability seen in the V4 region make it the most promising candidate to date for a barcode marker for diatoms particularly when combined with DNA character analysis.
| S-EPMC3448646 | biostudies-literature
Project description:Metabarcoding is a powerful tool for exploring microbial diversity in the environment, but its accurate interpretation is impeded by diverse technical (e.g. PCR and sequencing errors) and biological biases (e.g. intra-individual polymorphism) that remain poorly understood. To help interpret environmental metabarcoding datasets, we investigated the intracellular diversity of the V4 and V9 regions of the 18S rRNA gene from Acantharia and Nassellaria (radiolarians) using 454 pyrosequencing. Individual cells of radiolarians were isolated, and PCRs were performed with generalist primers to amplify the V4 and V9 regions. Different denoising procedures were employed to filter the pyrosequenced raw amplicons (Acacia, AmpliconNoise, Linkage method). For each of the six isolated cells, an average of 541 V4 and 562 V9 amplicons assigned to radiolarians were obtained, from which one numerically dominant sequence and several minor variants were found. At the 97% identity, a diversity metrics commonly used in environmental surveys, up to 5 distinct OTUs were detected in a single cell. However, most amplicons grouped within a single OTU whereas other OTUs contained very few amplicons. Different analytical methods provided evidence that most minor variants forming different OTUs correspond to PCR and sequencing artifacts. Duplicate PCR and sequencing from the same DNA extract of a single cell had only 9 to 16% of unique amplicons in common, and alignment visualization of V4 and V9 amplicons showed that most minor variants contained substitutions in highly-conserved regions. We conclude that intracellular variability of the 18S rRNA in radiolarians is very limited despite its multi-copy nature and the existence of multiple nuclei in these protists. Our study recommends some technical guidelines to conservatively discard artificial amplicons from metabarcoding datasets, and thus properly assess the diversity and richness of protists in the environment.
| S-EPMC4121268 | biostudies-literature
Project description:18S rDNA V4 region of environmental samples Raw sequence reads
| PRJNA910243 | ENA