Bowtie2
Overview
Bowtie2 is an ultrafast and memory-efficient tool for aligning sequencing reads to long reference sequences. It is particularly good at aligning reads of about 50 up to 100s or 1,000s of characters to relatively long (e.g. mammalian) genomes.
Bowtie 2 is not a “drop-in” replacement for Bowtie 1. Bowtie 2’s command-line arguments and genome index format are both different from Bowtie 1’s. See the section in the bowtie2 manual on how they differ.
Restrictions on use
All users may access and use Bowtie. The software is open source using the GPL3 license. Users should consult the following file for further information:
$BOWTIE2_HOME/LICENSE
For citation information see the Bowtie2 website.
Set up procedure
Please load one of the following modulefiles – we recommend doing this in your jobscript:
module load apps/binapps/bowtie2/2.5.4 module load apps/binapps/bowtie2/2.4.1
The previous version required two commands:
module load apps/bioinf libs/gcc/system module load apps/bowtie2/2.2.6/gcc-4.8.5
Indexes – for both versions no pre-built indexes have been installed. Users should download and build their own indexes and set the variable BOWTIE2_INDEXES on the command line or in .bashrc . For example, in your scratch area:
export BOWTIE2_INDEXES=$HOME/scratch/my_indexes
Running the application
Please do not run bowtie2 commands on the login node. qrsh is recommended for some commands. Computationally intense work should be done via the batch system.
Examples
The following example first runs bowtie2-build as a serial job. We then run bowtie2 using multi-core processing.
To create an index for the Lambda phage reference genome included with Bowtie 2, create a jobscript containing:
#!/bin/bash --login #SBATCH -p serial # (or --partition=) 1-core job #SBATCH -t 4-0 # 4-day wallclock (max permitted is 7 days) # Start with a clean environment in Slurm module purge module load apps/binapps/bowtie2/2.4.1 bowtie2-build $BOWTIE2_HOME/example/reference/lambda_virus.fa lambda_virus
and submit the job using sbatch jobscript where jobscript is the name of your job script file.
Now create a jobscript to run the Bowtie 2 aligner (bowtie2), which aligns a set of unpaired reads to the Lambda phage reference genome using the index generated in the previous step. We run this with multiple threads.
#!/bin/bash --login #SBATCH -p multicore # (or --partition=) Use the AMD 168-core nodes #SBATCH -n 8 # (or --ntasks=) Run in parallel with 8 threads (max is 168 in multicore) #SBATCH -t 2-0 # 2-day wallclock (7-0 is max permitted) # Start with a clean environment in Slurm module purge module load apps/binapps/bowtie2/2.4.1 # Use -p $SLURM_NTASKS to tell bowtie2 to use the number of threads requested above bowtie2 -p $SLURM_NTASKS -x lambda_virus -U $BOWTIE2_HOME/example/reads/reads_1.fq -S eg1.sam
and submit the job using sbatch jobscript where jobscript is the name of your job script file.
To view the first few lines of the output file use
head eg1.sam
Further info
- Bowtie 2 Manual
- Related applications available on the CSF:
- Panagiotis Papastamoulis, from FLS, has very kindly provided some documentaion illustrating how to use Cufflinks on the CSF which includes some Bowtie2 examples.