Bioinformatics Tools for Microbiome Analysis

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Data generated from microbiome experiments tends to require a distinct analytical approach, one that takes into account the many different organisms which may be present within a single biological sample. The considerations of sample preparation also tend to be fairly specific to the microbiome, e.g. 16S rRNA gene amplicon sequencing tends to be used only for the purpose of performing taxonomic identification for a mixture of bacteria.

The Microbiome Research Initiative was started at Fred Hutch to support and provide a community for scientists researching the microbiome, and part of that effort includes some work to develop a relatively standardized toolkit of bioinformatic analysis tools which can be used by multiple investigators across the center. This page is provided to host a description of analysis tools that are available, and will be updated as more are made available.

The tools below happen to use Nextflow as a system for running reproducible and portable analytical workflows. See this documentation for more details on running Nextflow at Fred Hutch, as well as the docs for more details on Nextflow itself.

For any questions on the tools presented here, either in trying to get them running on your data, or if you would like access to additional functionality (or would like to offer your own utilities), please contact Sam Minot (sminot@fredhutch.org).

Microbial RNAseq

One application of whole-genome shotgun sequencing (WGS) for microbiome research is the analysis of microbial mixtures on the basis of what microbes are present (DNA) or are transcriptionally active (RNA). To address this analytical need, we developed an analysis tool which takes a set of WGS input data and aligns it against a set of whole microbial genomes. With the orientation towards RNAseq, the tool takes a parameter --min_cov_pct which limits the analysis to those organisms which have greater than the specified level of coverage across the rRNA genes found in their genomes. Using just those organisms, the pipeline will then measure the depth of sequencing across all genes for all organisms across all samples, and provide those results to the user in the form of a set of CSV files.

GitHub repository: https://github.com/FredHutch/microbial-rnaseq

Example Run:

All input files are specified in a single file batchfile.csv which notes each sample with the columns name and fastq (fastq1 and fastq2 for paired-end data).

nextflow \
    run \
    fredhutch/microbial-rnaseq \
    --batchfile batchfile.csv \
    --host_genome "s3://fh-ctr-public-reference-data/tool_specific_data/microbial-rnaseq/2019-06-10/Homo_sapiens_assembly38.fasta.tar" \
    --database_folder "s3://fh-ctr-public-reference-data/tool_specific_data/microbial-rnaseq/2019-07-03/" \
    --database_prefix 2019-07-03-rnaseq-database \
    --min_cov_pct 90 \
    --output_folder results/ \
    --output_prefix 2019-05-08-test \
    -work-dir work/ \
    -resume

Viral Metagenomics

When studying viruses in the human microbiome, one fruitful approach can simply be to perform whole-genome shotgun sequencing (WGS) and then align all reads against a set of viruses from some reference database. This is an extremely parallelizable process, and therefore benefits heavily from execution systems like Nextflow which can distribute tasks to cloud computing services (like AWS).

This utility takes a set of input files (FASTQ format) and aligns them all against a set of viral genomes (specified by NCBI accession in a provided CSV file).

GitHub repository: https://github.com/FredHutch/nf-viral-metagenomics

Example Run:

<INPUT_DIRECTRY> contains the set of FASTQ files to analyze <OUTPUT_DIRECTRY> is the location where all outputs will be placed <VIRAL_GENOME_CSV> is a CSV with a column accession containing the set of viral genomes to align against (as NCBI Nucleotide accessions) <NAME_OF_OUTPUT_CSV> is the name of the output file to be placed in the <OUTPUT_DIRECTORY>

nextflow \
    run \
        FredHutch/nf-viral-metagenomics \
        --input_directory <INPUT_DIRECTORY> \
        --output_directory <OUTPUT_DIRECTORY> \
        --viral_genome_csv <VIRAL_GENOME_CSV> \
        --output_csv <NAME_OF_OUTPUT_CSV>

Updated:

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