con-hi

“Con-hi” means “consensus-highlighter”.

Latest version is 4.1.a (2026-03-18 edition).

Description

This program annotates low-coverage and high-coverage regions of sequences in fasta format using read mapping in BAM format.

Input

1. Target sequence(s) in fasta format.
2. Read mapping in a sorted BAM file.
3. Coverage threshold(s) for searching low-coverage and high-coverage regions.

Output

• A GenBank or BED file with annotated low-coverage and high-coverage regions.

Dependencies

• Python 3.6 or later.
• Biopython package.
• samtools 1.13 or later is recommended. Versions from 1.11 to 1.12 are acceptable, but might calculate coverage inaccurately.

You can install Biopython with following command:

pip3 install biopython

You can install samtools by downloading latest release from samtools page on github. Then follow instrunctions in downloaded INSTALL file.

Usage

Basic usage is:

./con-hi.py -f <TARGET_FASTA> -b <MAPPING_BAM>

You can specify custom coverage theshold(s) by passing comma-separated list of thresholds with options -c, -C and -X. For example, following command will annotate:

• regions with coverage below 25 and all regions below 55 (and also with zero coverage);

• regions with coverage greater than 1.5×M and greater than 2.0×M, where M is median coverage.

./con-hi.py \
    -f my_sequence.fasta -b my_mapping.sorted.bam \
    -c 25,55 -X 1.5,2.0

Options

-f or --target-fasta: *
    File of target sequence(s) in fasta format.

-b or --bam: *
    Sorted BAM file which contains mapping on target sequence(s).

-o or --outfile:
    Output file.
    Deault value: 'highlighted_sequence.gbk'.

-O or --output-format:
    Output format: `genbank` or `bed`.
    Default: `genbank`.

-r or --target-seq-ids:
    Comma-separated list of target sequence IDs to process.
    Examples: "seq_1" or "seq_1,seq_9,seq_12".
    Dasta sequence id is the part of its header before the first space.
    Default: process all target sequences.

-c or --lower-coverage-thresholds:
    Comma-separated list of lower coverage threshold(s).
    To annotate regions with coverage < c.
    Default: 10.
    To disable it, specify "-c off", and low-coverage regions won't be annotated.

-C or --upper-coverage-thresholds:
    Comma-separated list of upper coverage threshold(s).
    To annotate regions with coverage > C.
    Default: 500.
    To disable it, specify "-C off", and high-coverage regions won't be annotated.

-n or --no-zero-output:
    Disable annotation of zero-coverage regions.
    Disabled by default.

-X or --upper-coverage-coefficients:
    Comma-separated list of coverage coefficient(s).
    To annotate regions with coverage > 1.7×M,
      where M is median coverage, specify "-X 1.7".
    Default: 2.0.
    To disable it, specify "-X off", and high-coverage regions won't be annotated.

-l or --min-feature-len:
    Minimum length of a feature to output. Must be int >= 0.
    Default: 5 bp.

--circular:
    Target sequence in curcular. Affects only corresponding GenBank field.
    Disabled by default.
    
--organism:
    Organism name. Affects only corresponding GenBank field.
    If it contains spaces, surround it with quotes (see Example 4).
    Empty by default.

-k or --keep-temp-cov-file:
    Don't delete temporary TSV file "coverages.tsv" after work of the program.
    The program creates this file in the same directory where the "-o" file is located.
    Default behaviour is to delete this file afterwards.

* - mandatory option

Examples

Example 1. Basic usage

Annotate file my_sequence.fasta with default parameters according to mapping from file my_mapping.sorted.bam:

./con-hi.py -f my_sequence.fasta -b my_mapping.sorted.bam

Example 2. How to use -c and -C options

Annotate regions with coverage below 25, fragments with coverages below 50 and regions with zero coverages:

./con-hi.py -f my_sequence.fasta -b my_mapping.sorted.bam -c 25,50

Annotate regions with coverage above 25 and fragments with coverages above 50:

./con-hi.py -f my_sequence.fasta -b my_mapping.sorted.bam -C 25,50

Example 3. How to use options -c, -n

Annotate regions with coverage below 25, fragments with coverages below 50. Disable annotation of zero coverage regions:

./con-hi.py -f my_sequence.fasta -b my_mapping.sorted.bam -c 25,50 -n

Example 4. How to use options --circular, --organism

Specify the name of the organism for output file. The sequence is circular:

./con-hi.py -f my_sequence.fasta -b my_mapping.sorted.bam \
    --circular --organism "Serratia marcescens"

Example 5. How to turn off annotation of low-coverage regions (-c off) and use -X options

Disable annotation of low-coverage regions (-c off). Annotate high-coverage regions with coverage above 1.7×M and above 2.4×M (where M is median coverage) using -X option:

./con-hi.py -f my_sequence.fasta -b my_mapping.sorted.bam \
    -c off -X 1.7,2.4

Example 6. How to use -r option

Target file my_sequences.fasta contains the following sequences:

1. a prokaryotic chromosome (sequence id chr);

2. one high-copy plasmid (sequence id plasmid_H1);

3. two low-copy plasmids (sequence ids plasmid_L1 and plasmid_L2).

One might expect that the more copies a replicon has the higher is its read coverage. Use coverage threshold of 20 for the chromosome, 50 for the high-copy plasmid, and 5 for low-copy plasmids:

./con-hi.py -f my_sequences.fasta -b my_mapping.sorted.bam \
    -r chr \
    -c 20

./con-hi.py -f my_sequences.fasta -b my_mapping.sorted.bam \
    -r plasmid_H1 \
    -c 50

./con-hi.py -f my_sequences.fasta -b my_mapping.sorted.bam \
    -r plasmid_L1,plasmid_L2 \
    -c 5

Example 7. How to use -O option

Output results in BED format instead of GenBank:

./con-hi.py -f my_sequence.fasta -b my_mapping.sorted.bam -O bed