Assembly and intrahost/low-frequency variant calling for viral samples

COVID-19: variation analysis reporting

This workflow takes table of variants produced by any of the other four variant calling workflows in https://github.com/galaxyproject/iwc/tree/main/workflows/sars-cov-2-variant-calling and generates a list of variants by Samples and by Variant.

COVID-19: variation analysis on WGS SE data

This workflows performs single end read mapping with bowtie2 followed by sensitive variant calling across a wide range of AFs with lofreq and variant annotation with snpEff 4.5covid19.

COVID-19: variation analysis on WGS PE data

This workflows performs paired end read mapping with bwa-mem followed by sensitive variant calling across a wide range of AFs with lofreq and variant annotation with snpEff 4.5covid19.

COVID-19: variation analysis on ARTIC PE data

The workflow for Illumina-sequenced ARTIC data builds on the RNASeq workflow for paired-end data using the same steps for mapping and variant calling, but adds extra logic for trimming ARTIC primer sequences off reads with the ivar package. In addition, this workflow uses ivar also to identify amplicons affected by ARTIC primer-binding site mutations and, if possible, excludes reads derived from such ...

COVID-19: variation analysis on ARTIC ONT data

This workflow for ONT-sequenced ARTIC data is modeled after the alignment/variant-calling steps of the ARTIC pipeline. It performs, essentially, the same steps as that pipeline’s minion command, i.e. read mapping with minimap2 and variant calling with medaka. Like the Illumina ARTIC workflow it uses ivar for primer trimming. Since ONT-sequenced reads have a much ...

COVID-19: consensus construction

This workflow aims at generating reliable consensus sequences from variant calls according to transparent criteria that capture at least some of the complexity of variant calling.

It takes a collection of VCFs and a collection of the corresponding aligned reads (for the purpose of calculating genome-wide coverage) such as produced by any of the four variant calling workflows in https://github.com/galaxyproject/iwc/tree/main/workflows/sars-cov-2-variant-calling ...

COVID-19: variation analysis on ARTIC ONT data

This workflow for ONT-sequenced ARTIC data is modeled after the alignment/variant-calling steps of the ARTIC pipeline. It performs, essentially, the same steps as that pipeline’s minion command, i.e. read mapping with minimap2 and variant calling with medaka. Like the Illumina ARTIC workflow it uses ivar for primer trimming. Since ONT-sequenced reads have a much ...

COVID-19: variation analysis on WGS PE data

This workflows performs paired end read mapping with bwa-mem followed by sensitive variant calling across a wide range of AFs with lofreq and variant annotation with snpEff 4.5covid19.

COVID-19: variation analysis on WGS PE data

This workflows performs single end read mapping with bowtie2 followed by sensitive variant calling across a wide range of AFs with lofreq and variant annotation with snpEff 4.5covid19.

COVID-19: variation analysis on ARTIC PE data

The workflow for Illumina-sequenced ARTIC data builds on the RNASeq workflow for paired-end data using the same steps for mapping and variant calling, but adds extra logic for trimming ARTIC primer sequences off reads with the ivar package. In addition, this workflow uses ivar also to identify amplicons affected by ARTIC primer-binding site mutations and excludes reads derived from such "tainted" amplicons ...

Preprocessing of raw SARS-CoV-2 reads

The raw reads available so far are generated from bronchoalveolar lavage fluid (BALF) and are metagenomic in nature: they contain human reads, reads from potential bacterial co-infections as well as true COVID-19 reads.

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nf-core/vipr is a bioinformatics best-practice analysis pipeline for assembly and intrahost / low-frequency variant calling for viral samples. The pipeline is built using Nextflow, a workflow tool to run tasks across multiple compute infrastructures in a very portable manner. It comes with docker / singularity containers making installation trivial and results highly reproducible. Pipeline Steps

Step Main program/s

Trimming, combining of read-pairs per sample and QC Skewer, FastQC

Decontamination ...

nfcore/viralrecon is a bioinformatics analysis pipeline used to perform assembly and intrahost/low-frequency variant calling for viral samples. The pipeline currently supports metagenomics and amplicon sequencing data derived from the Illumina sequencing platform. This pipeline is a re-implementation of the SARS_Cov2_consensus-nf and SARS_Cov2_assembly-nf pipelines initially developed by Sarai Varona and Sara Monzon from BU-ISCIII. Porting both of these pipelines to nf-core was an international ...

Evolutionary Analysis

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What's the point?

Wu et al. showed recombination between COVID-19 and bat coronaviruses located within the S-gene. We want to confirm this observation and provide a publicly accessible workflow for recombination detection.

In previous coronavirus outbreaks (SARS), retrospective analyses determined that adaptive substitutions might have occurred in the S-protein Zhang et al., e.g., related to ACE2 receptor ...

Analysis of S-protein polymorphism

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What's the point?

In the previous portion of this study we found a non-synonymous polymorphism within the S-gene. In this section we are trying to interpret its possible effect.

Outline

Obtain coding sequences of S proteins from a diverse group of coronaviruses. Generate amino acid alignment to assess conservation of the polymorphic location.

Input

Downloaded CDS sequences of coronavirus ...

Analysis of variation within individual COVID-19 samples | March 20 2020

What's the point?

The absolute majority of SARS-COV-2 data is in the form of assembled genomic sequences. This is unfortunate because any variation that exists within individual samples is obliterated--converted to the most frequent base--during the assembly process. However, knowing underlying evolutionary dynamics is critical for tracing evolution of the virus as it allows identification of genomic regions under different ...

Dating the most recent common ancestor (MRCA) of SARS-CoV-2

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What's the point?

To estimate the time of COVID-19 emergence we use simple root-to-tip regression (Korber et al. 2000; more complex and powerful phylodynamics methods could certainly be used, but for this data with very low levels of sequence divergence, simpler and faster methods suffice). From the set of all COVID-19 sequences available as of Feb 16, 2020 we obtain ...

Assembly of SARS-CoV-2 from pre-processed reads

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What's the point?

Use a combination of Illumina and Oxford Nanopore reads to produce SARS-CoV-2 genome assembly.

Outline

We use Illumina and Oxford Nanopore reads that were pre-processed to remove human-derived sequences. We use two assembly tools: spades and unicycler. While spades is a tool fully dedicated to assembly, unicycler is a "wrapper" that combines multiple existing ...

Preprocessing of raw SARS-CoV-2 reads

The raw reads available so far are generated from bronchoalveolar lavage fluid (BALF) and are metagenomic in nature: they contain human reads, reads from potential bacterial co-infections as well as true COVID-19 reads.

Live Resources

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What's the point?

Assess quality of reads, remove adapters and remove reads mapping to human genome.

The outline

Illumina and Oxford nanopore reads are pulled from the ...