fasta_filter

This little tool accept a fasta file (or from stdin), and out put a filtered fasta file (or to stdout). It is (relatively) fast, see comparison between a simple python implementation.

Usage:

fasta_filter 0.1.4
Haogao Gu <koohoko@gmail.com>
A tool for filtering fasta sequences with threshold of specific bases (e.g. 'N'), written in Rust.

USAGE:
    fasta_filter [OPTIONS] --file <FILE> --num_base <NUMBER>

OPTIONS:
    -f, --file <FILE>
            Path of fasta file or use '-' as stdin.

    -b, --base <STRING>
            Bases to be accounted for. Examples: "N,-". Please note that this is case sensitive.
            [default: N]

    -n, --num_base <NUMBER>
            Frequency of specified bases, any sequences with bases count over this threshold will
            not be print out. Use 0 to skip this step if you only want to use the specified_pos
            filter.

    -s, --specified_pos_file <FILE>
            Path to a txt file specifying genomic positions of interest, each line should contain
            one integer specifying nucleotide position. Positions are 1-based rather than 0-based.

    -m, --specified_num_base <NUMBER>
            The num_base threshold for the specified positions.

    -o, --out_file <NUMBER>
            Path to write to the outfile, if "-" will write to stdout. [default: -]

    -v, --verbose
            Add this flap to print parameters to stderr.

    -h, --help
            Print help information

    -V, --version
            Print version information

Installation

Executable

Directly download executables from Releases.

Install from source

1. Install Rust from here.
2. Download source code by git clone https://github.com/Koohoko/fasta_filter.git.
3. Install with cargo install --path fasta_filter.
4. You are ready to go.

Examples

Example input:

>seq1_8N_5del
NNNAAAAAAAAAAAAACCCCCCCCCCCTTTTTTTTGGGGGGGGGGGGGGGGAAACCC-----AAAAAANNNNNTTTTT
>seq2_20N_10del
NNNAAAAAAAAA-----CCCCCCCCCTTTTTTTTGGGGGGGNNNNNNNGGAAACCC-----AAAAAANNNNNNNNNNT
>seq1_5N_5del
TTTAAAAAAAAAAAAACCCCCCCCCCCTTTTTTTTGGGGGGGGGGGGGGGGAAACCC-----AAAAAANNNNNTTTTT

Example usage:

• Drop the sequences with > 5 "N" bases:

✗ fasta_filter -b N -n 5 -f data/small.fasta
>seq3_5N_5del
TTTAAAAAAAAAAAAACCCCCCCCCCCTTTTTTTTGGGGGGGGGGGGGGGGAAACCC-----AAAAAANNNNNTTTTT

• Drop the sequences with > 20 "N"+"-" bases:

✗ fasta_filter -b N,- -n 20 -f data/small.fasta 
>seq1_8N_5del
NNNAAAAAAAAAAAAACCCCCCCCCCCTTTTTTTTGGGGGGGGGGGGGGGGAAACCC-----AAAAAANNNNNTTTTT
>seq3_5N_5del
TTTAAAAAAAAAAAAACCCCCCCCCCCTTTTTTTTGGGGGGGGGGGGGGGGAAACCC-----AAAAAANNNNNTTTTT

• Drop the sequences with > 2 "N bases within specified positions (positions are specified in a txt file). Here we use "-n 0" to skip the full genome filter:

✗ fasta_filter -b N -n 0 -f data/small.fasta -s ./data/mut_pos.txt -m 2
>seq2_20N_10del
NNAAAAAAAAAA-----CCCCCCCCCTTTTTTTTGGGGGGGNNNNNNNGGAAACCC-----AAAAAANNNNNNNNNNT
>seq3_5N_5del
TTTAAAAAAAAAAAAACCCCCCCCCCCTTTTTTTTGGGGGGGGGGGGGGGGAAACCC-----AAAAAANNNNNTTTTT

• filtering both specified positions and the full genome with different threshold:

✗ fasta_filter -b N -n 10 -f data/small.fasta -s ./data/mut_pos.txt -m 2
>seq3_5N_5del
TTTAAAAAAAAAAAAACCCCCCCCCCCTTTTTTTTGGGGGGGGGGGGGGGGAAACCC-----AAAAAANNNNNTTTTT

• Input compressed files and output to a regular fasta file, showing verbose info:

✗ fasta_filter -b N -n 10 -f data/small.fasta.xz -s ./data/mut_pos.txt -m 2 -v -o ./data/test_output.fasta
### Job started! ###

fasta file: data/small.fasta.xz
Output file: ./data/test_output.fasta
bases: ['N']
num_base: 10
allow_iupac: true
specified_pos_file: ./data/mut_pos.txt
specified_num_base: 2

### Job finished! ###

✗ cat ./data/test_output.fasta 
>seq1_8N_5del
TTTAAAAAAAAAAAAACCCCCCCCCCCTTTTTTTTGGGGGGGGGGGGGGGGAAACCC-----AAAAAANNNNNTTTTT

Benchmark

• Runing on plain fasta file containing SASR-CoV-2 sequences (it is 1.5GB in file size, and contains 50,000 sequences (length of each sequence ~ 29900)). When output to /dev/null, fasta_filter used ~0.6s and the python3 one used ~12s on my poor computer (Intel NUC8i5beh). Details can be found here (Rust, Python).

• Using filter_fasta with double filters for a big fasta file (302GB in plain text, multiple sequence alignment of SARS-CoV-2 downloaded from GISAID). IO seems to be the major bottleneck.

✗ time -hl fasta_filter -f /Volumes/SSD_480G/Downloads/msa_2022-04-04/2022-04-04_unmasked.fa -b n,-,N -n 4500 -m 10 -s ./data/BA1_BA2_pos.txt -o /Users/koohoko/Downloads/2022-04-04_unmasked_filtered.fasta 
	10m7.61s real		2m52.32s user		4m44.53s sys
             1458176  maximum resident set size
                   0  average shared memory size
                   0  average unshared data size
                   0  average unshared stack size
                 521  page reclaims
                   1  page faults
                   0  swaps
                   0  block input operations
                   7  block output operations
                   0  messages sent
                   0  messages received
                   0  signals received
               27170  voluntary context switches
             1002349  involuntary context switches
       2358390178277  instructions retired
       1400439339433  cycles elapsed
              618496  peak memory footprint

TODO / PLANS

• Test pipe streams. Stdin and Stdout work as expected.
• Test zip files. gz and xz inputs are also supported.
• Benchmark against python implementation.
• Add installation instruction.
• Work in multithread mode?

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