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Mapping-Assisted Targeted-Assembly for Metagenomics
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README.md

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Mapping-Assisted Targeted-Assembly for Metagenomics

MATAM is a software dedicated to the fast and accurate targeted assembly of short reads sequenced from a genomic marker of interest. It has been applied to the assembly of 16S rRNA markers and is validated on simulated, synthetic and genuine metagenomes.

The related article of this method is available here.

Table of contents

1. Hardware requirements

We recommend running MATAM with at least 10Go of free RAM. You can try running MATAM with less RAM by setting --max_memory to a lower value (eg. --max_memory 4000 for 4Go). However, this could degrade the performance of the software.

Some steps of MATAM are highly parallelized. So you can get a significant speed up by setting the --cpu option according to your hardware configuration.

2. Installation

There are three possible ways of installing MATAM: either with CONDA, or as a docker container, or directly from the source code.

2.1 MATAM with conda

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Before you begin, you should have installed Miniconda or Anaconda. See https://docs.conda.io/projects/conda/en/latest/user-guide/install/ for more details.
Then you will need to add the followings channels:

conda config --add channels defaults
conda config --add channels bioconda
conda config --add channels conda-forge

Finally, matam can be installed with:

conda install -c bioconda matam

All the commands used in this README will be available in your PATH.

2.2 MATAM in Docker

To retrieve the docker image, run the following command:

docker pull quay.io/biocontainers/matam:{release_version}

Then all the commands used in this README will be available as:

docker run -v host_directory:/workdir quay.io/biocontainers/matam:{release_version} CMD

Noticed that you have to specify a docker volume to share data between the host and the container and use this workdir for your analysis. Otherwise your data will be lost when exiting the container.

Finally, if you prefer an interactive session with the container, run:

docker run -it quay.io/biocontainers/matam:{release_version}

2.3 MATAM from source code

To install all of the needed dependencies you need conda installed. See the following section for more details on how to configure conda.

Then run the following commands:

  1. Cloning MATAM repository

git clone https://github.com/bonsai-team/matam.git && cd matam

  1. Install dependencies: conda env create -f environment.yml && conda activate matam

  2. Compile MATAM

./build.py

  1. Update your PATH to make MATAM's commands available:
echo 'export PATH="$MATAMDIR/bin:$PATH"' >> ~/.profile
source ~/.profile

3. Run MATAM

3.1 Input data

The reads used to reconstruct the markers must be provided under FASTQ format.
Be aware than the the sequence identifiers have to be unique and the the score must be Phred+33 encoded.

3.2 Database preparation (clustering & indexation)

3.2.1 Provided database

By default, MATAM provides a SSU rRNA reference database where the clusterisation step has already been done (i.e. the sequences sharing 95% of identity have been clustered with Sumaclust).
The FASTA file used for this database comes from SILVA 128 release.

To use the default SSU rRNA reference database, run the following command:

index_default_ssu_rrna_db.py -d $DBDIR --max_memory 10000

where $DBDIR is the directory used to store the database.

3.2.2 Custom database

If the provided database does not fulfill your needs, you can prepare a custom database of your own by running the following command:

matam_db_preprocessing.py -i ref_db.fasta -d $DBDIR --cpu 4 --max_memory 10000 -v

where $DBDIR is the directory used to store the database.

3.3 De-novo assembly

When your database is ready, then you will be able to reconstruct your markers:

  • Assembly only
    In this mode, MATAM will reconstruct the full length sequences present in the sample.
    matam_assembly.py -d $DBDIR/prefix -i reads.fastq --cpu 4 --max_memory 10000 -v

  • Assembly and taxonomic assignment
    In this mode, MATAM additionnaly provides a taxonomic classification of the sequences found, together with their abundance. Note that the classification is done with RDP with the default training model "16srrna". So this mode may be not suitable for other phylogenetic markers.
    matam_assembly.py -d $DBDIR/prefix -i reads.fastq --cpu 4 --max_memory 10000 -v --perform_taxonomic_assignment
    The taxonomic assignment is done with RDP classifier and the training model used by default is "16srrna"

where $DBDIR is the database directory and prefix is the common prefix used to name the database files. For example, with the default database, the prefix is SILVA_128_SSURef_NR95.

3.4 Example with default database and provided dataset

  1. Retrieve the example dataset: 16 bacterial species simulated dataset

wget https://raw.githubusercontent.com/bonsai-team/matam/master/examples/16sp_simulated_dataset/16sp.art_HS25_pe_100bp_50x.fq

  1. Getting and indexing default SSU rRNA reference database

index_default_ssu_rrna_db.py -d $DBDIR --max_memory 10000

  1. De-novo assembly

matam_assembly.py -d $DBDIR/SILVA_128_SSURef_NR95 -i 16sp.art_HS25_pe_100bp_50x.fq --cpu 4 --max_memory 10000 -v --perform_taxonomic_assignment

4. Samples comparaison

We provide a script to compare the abundances of different samples. Available only if the --perform_taxonomic_assignment was used when running MATAM.

matam_compare_samples.py -s samples_to_compare.tsv -t contingency_table.tsv -c comparaison_table.tsv

The samples_to_compare.tsv file is a tabulated file listing the FASTA & RDP files of each sample to compare (see example below).
The contingency_table.tsv file will report the abundance for each sequence.
The comparaison_table.tsv file will report a comparaison by "taxonomic path" of the abundance for the samples.

Example

sample1 <tab> $WORKDIR/matam_sample1/final_assembly.fa <tab> $WORKDIR/matam_sample1/rdp.tab
sample2 <tab> $WORKDIR/matam_sample2/final_assembly.fa <tab> $WORKDIR/matam_sample2/rdp.tab

The first column is the ID of the sample and it must be unique among the file.

5. Release versioning

MATAM releases will be following the Semantic Versioning 2.0.0 rules described here: http://semver.org/spec/v2.0.0.html

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