Create BIOM-format tables from Kraken output.

kraken, BIOM, metagenomics, bioinformatics, taxonomy, biom-format, taxonomic-classification
pip install kraken-biom==1.0.1



Travis CI build status

Create BIOM-format tables ( from Kraken output (


From PyPI:

$ pip install kraken-biom

From GitHub:

$ pip install git+

From source:

$ python install


  • biom-format >= 2.1.5


The program takes as input, one or more files output from the kraken-report tool. Each file is parsed and the counts for each OTU (operational taxonomic unit) are recorded, along with database ID (e.g. NCBI), and lineage. The extracted data are then stored in a BIOM table where each count is linked to the Sample and OTU it belongs to. Sample IDs are extracted from the input filenames (everything up to the '.').

OTUs are defined by the --max and --min arguments. By default these are set to Order and Species respectively. This means that counts assigned directly to an Order, Family, or Genus are recorded under the associated OTU ID, and counts assigned at or below the Species level are assigned to the OTU ID for the species. Setting a minimum rank below Species is not yet available.

The BIOM format currently has two major versions. Version 1.0 uses the JSON (JavaScript Object Notation) format as a base. Version 2.x uses the HDF5 (Hierarchical Data Format v5) as a base. The output format can be specified with the --fmt option. Note that a tab-separated (tsv) output format is also available. The resulting file will not contain most of the metadata, but can be opened by spreadsheet programs.

Version 2 of the BIOM format is used by default for output, but requires the Python library 'h5py'. If the library is not installed, kraken-biom will automatically switch to using version 1.0. Note that the output can optionally be compressed with gzip (--gzip) for version 1.0 and TSV files. Version 2 files are automatically compressed.

Currently the taxonomy for each OTU ID is stored as row metadata in the BIOM table using the standard seven-level QIIME format: k__K; p__P; ... s__S. If you would like another format supported, please file an issue or send a pull request (note the contribution guidelines).

usage: [-h] [--max {D,P,C,O,F,G,S}] [--min {D,P,C,O,F,G,S}]
                      [-o OUTPUT_FP] [--fmt {hdf5,json,tsv}] [--gzip]
                      [--version] [-v]
                      kraken_reports [kraken_reports ...]

Usage examples

  1. Basic usage with default parameters:

    $ S1.txt S2.txt
This produces a compressed BIOM 2.1 file: table.biom
  1. BIOM v1.0 output:

    $ S1.txt S2.txt --fmt json
Produces a BIOM 1.0 file: table.biom
  1. Compressed TSV output:

    $ S1.txt S2.txt --fmt tsv --gzip -o table.tsv
Produces a TSV file: table.tsv.gz
  1. Change the max and min OTU levels to Class and Genus:

    $ S1.txt S2.txt --max C --min G

Program arguments

positional arguments:

kraken_reports        Results files from the kraken-report tool.

optional arguments:

-h, --help            show this help message and exit
--max {D,P,C,O,F,G,S}
                      Assigned reads will be recorded only if they are at or
                      below max rank. Default: O.
--min {D,P,C,O,F,G,S}
                      Reads assigned at and below min rank will be recorded
                      as being assigned to the min rank level. Default: S.
-o OUTPUT_FP, --output_fp OUTPUT_FP
                      Path to the BIOM-format file. By default, the table
                      will be in the HDF5 BIOM 2.x format. Users can output
                      to a different format using the --fmt option. The
                      output can also be gzipped using the --gzip option.
                      Default path is: ./table.biom
--fmt {hdf5,json,tsv}
                      Set the output format of the BIOM table. Default is
--gzip                Compress the output BIOM table with gzip. HDF5 BIOM
                      (v2.x) files are internally compressed by default, so
                      this option is not needed when specifying --fmt hdf5.
--version             show program's version number and exit
-v, --verbose         Prints status messages during program execution.