Hostile

Hostile removes host sequences from short and long reads, consuming paired or unpaired fastq[.gz] input and producing fastq.gz output. Batteries are included – Hostile downloads and saves a human T2T-CHM13v2.0 + HLA reference genome to $XDG_DATA_DIR when run for the first time. Read headers are replaced with incrementing integers for privacy and more compressible FASTQs. Hostile is implemented as a Python package with a CLI and Python API, but all of the heavy lifting is done by fast compiled code (Minimap2/Bowtie2 and Samtools). When used with a masked reference genome, Hostile achieves near-perfect retention of microbial reads while removing >99.5% of human reads. Please read the BioRxiv preprint for further information and open a GitHub issue, tweet or toot me to report bugs or suggest improvements.

Reference genomes

The default human-t2t-hla reference is downloaded when running Hostile for the first time. This can be overriden by specifying a custom --index. Bowtie2 indexes need to be untarred before use. The databases human-t2t-hla and human-t2t-hla-argos985-mycob140 were compared in the paper.

Install

Installation with Conda/Miniconda or Docker is recommended due to non-Python dependencies (Minimap2, Bowtie2, Samtools, Bedtools). Hostile is tested with Ubuntu Linux 22.04, MacOS 12, and WSL2.

Conda

curl -OJ https://raw.githubusercontent.com/bede/hostile/main/environment.yml
conda env create -f environment.yml  # Use Mamba if impatient
conda activate hostile
pip install hostile

Development install

git clone https://github.com/bede/hostile.git
cd hostile
conda env create -f environment.yml  # Use Mamba if impatient
conda activate hostile
pip install --editable '.[dev]'
pytest

Command line usage

$ hostile clean --help
usage: hostile clean [-h] --fastq1 FASTQ1 [--fastq2 FASTQ2] [--aligner {bowtie2,minimap2,auto}] [--index INDEX] [--rename] [--out-dir OUT_DIR] [--threads THREADS] [--force] [--debug]

Remove host reads from paired fastq(.gz) files

options:
  -h, --help            show this help message and exit
  --fastq1 FASTQ1       path to forward fastq(.gz) file
  --fastq2 FASTQ2       optional path to reverse fastq(.gz) file
                        (default: None)
  --aligner {bowtie2,minimap2,auto}
                        alignment algorithm
                        (default: auto)
  --index INDEX         path to custom genome or index. For Bowtie2, provide an index path without the .bt2 extension
                        (default: None)
  --rename              replace read names with incrementing integers
                        (default: False)
  --out-dir OUT_DIR     path to output directory
                        (default: ./)
  --threads THREADS     number of CPU threads to use
                        (default: 10)
  --force               overwrite existing output files
                        (default: False)
  --debug               show debug messages
                        (default: False)

Short reads

$ hostile clean --fastq1 reads.r1.fastq.gz --fastq2 reads.r2.fastq.gz
INFO: Using Bowtie2
INFO: Found cached index (/Users/bede/Library/Application Support/hostile/human-t2t-hla)
INFO: Cleaning…
[
    {
        "aligner": "bowtie2",
        "index": "/path/to/data/dir/human-t2t-hla",
        "fastq1_in_name": "reads.r1.fastq.gz",
        "fastq2_in_name": "reads.r2.fastq.gz",
        "fastq1_in_path": "/path/to/hostile/reads.r1.fastq.gz",
        "fastq2_in_path": "/path/to/hostile/reads.r2.fastq.gz",
        "fastq1_out_name": "reads.r1.clean_1.fastq.gz",
        "fastq2_out_name": "reads.r2.clean_2.fastq.gz",
        "fastq1_out_path": "/path/to/hostile/reads.r1.clean_1.fastq.gz",
        "fastq2_out_path": "/path/to/hostile/reads.r2.clean_2.fastq.gz",
        "reads_in": 20,
        "reads_out": 20,
        "reads_removed": 0,
        "reads_removed_proportion": 0.0
    }
]

Long reads

$ hostile clean --fastq1 tests/data/h37rv_10.r1.fastq.gz
INFO: Using Minimap2's long read preset (map-ont)
INFO: Found cached reference (/Users/bede/Library/Application Support/hostile/human-t2t-hla.fa.gz)
INFO: Cleaning…
[
    {
        "aligner": "minimap2",
        "index": "/Users/bede/Library/Application Support/hostile/human-t2t-hla.fa.gz",
        "fastq1_in_name": "reads.fastq.gz",
        "fastq1_in_path": "/path/to/hostile/reads.fastq.gz",
        "fastq1_out_name": "reads.clean.fastq.gz",
        "fastq1_out_path": "/path/to/hostile/reads.clean.fastq.gz",
        "reads_in": 10,
        "reads_out": 10,
        "reads_removed": 0,
        "reads_removed_proportion": 0.0
    }
]

Python usage

from pathlib import Path
from hostile.lib import clean_paired_fastqs, ALIGNER

# Short reads, defaults
clean_fastqs(
    fastqs=[(data_dir / "reads_1.fastq.gz", data_dir / "reads_2.fastq.gz")],
)

# Long reads, all the options, capture statistics
statistics = lib.clean_paired_fastqs(
    fastqs=[data_dir / "reads.fastq.gz"],
    aligner=ALIGNER.minimap2,
    index=data_dir / "reference.fasta.gz",
    out_dir=data_dir / "decontaminated-reads",
    threads=4
)

print(stats)

Masking reference genomes

The mask subcommand makes it easy to create custom-masked reference genomes and achieve maximum retention of specific target organisms:

hostile mask human.fasta lots-of-bacterial-genomes.fasta --threads 8

​ You may wish to use one of the existing reference genomes as a starting point. Masking uses Minimap2's asm10 preset to align the supplied target genomes with the reference genome, and bedtools to mask out all aligned regions. This feature requires a development install until release in version 0.0.3. For Bowtie2—the default aligner for decontaminating short reads—you will also need to build an index before you can use your masked genome with Hostile.

bowtie2-build masked.fasta masked-index
hostile clean --index masked-index --fastq1 reads_1.fastq.gz --fastq2 reads_2.fastq.gz