Bio-Tradis

Bio-Tradis contains a set of tools to analyse the output from TraDIS analyses. For more information on the TraDIS method, see http://genome.cshlp.org/content/19/12/2308

Bio-Tradis provides functionality to:

• detect TraDIS tags in a BAM file
• add the tags to the reads
• filter reads in a FastQ file containing a user defined tag
• remove tags
• map to a reference genome
• create an insertion site plot file available as standalone scripts or as perl modules.

It requires the htslib version of samtools http://www.htslib.org/

Objects and Methods

####Bio::Tradis::DetectTags

• Required parameters:
  • bamfile - path to/name of file to check
• Methods:
  • tags_present - returns true if TraDIS tags are detected in bamfile

####Bio::Tradis::AddTagsToSeq

• Required parameters:
  • bamfile - path to/name of file containing reads and tags
• Optional parameters:
  • outfile - defaults to file.tr.bam for an input file named file.bam
• Methods:
  • add_tags_to_seq - add TraDIS tags to reads. For unmapped reads, the tag is added to the start of the read sequence and quality strings. For reads where the flag indicates that it is mapped and reverse complemented, the reverse complemented tags are added to the end of the read strings. This is because many conversion tools (e.g. picard) takes the read orientation into account and will re-reverse the mapped/rev comp reads during conversion, leaving all tags in the correct orientation at the start of the sequences in the resulting FastQ file.

####Bio::Tradis::FilterTags

• Required parameters:
  • fastqfile - path to/name of file to filter. This may be a gzipped fastq file, in which case a temporary unzipped version is used and removed on completion.
  • tag - TraDIS tag to match
• Optional parameters:
  • mismatch - number of mismatches to allow when matching the tag. Default = 0
  • outfile - defaults to file.tag.fastq for an input file named file.fastq
• Methods:
  • filter_tags - output all reads containing the tag to outfile

####Bio::Tradis::RemoveTags

• Required parameters:
  • fastqfile - path to/name of file to filter.
  • tag - TraDIS tag to remove
• Optional parameters:
  • mismatch - number of mismatches to allow when removing the tag. Default = 0
  • outfile - defaults to file.rmtag.fastq for and input file named file.fastq
• Methods:
  • remove_tags - output all reads with the tags removed from both sequence and quality strings to outfile

####Bio::Tradis::Map

• Required parameters:

  • fastqfile - path to/name of file to map to the reference
  • reference - path to/name of reference genome in fasta format (.fa)

• Optional parameters:

  • refname - name to assign to the reference index files. Default = ref.index
  • outfile - name to assign the mapped SAM file. Default = mapped.sam

• Methods:

  • index_ref - create index files of the reference genome. These are required for the mapping step. Only skip this step if index files already exist. -k and -s options for referencing are calculated based on the length of the reads being mapped:
    • <70 : -k 13 -s 4

    • 70 & <100 : -k 13 -s 6

    • 100 : -k 20 -s 13

  • do_mapping - map fastqfile to reference. Options used for mapping are: -r -1, -x and -y 0.96

  For more information on the mapping and indexing options discussed here, see the SMALT manual (ftp://ftp.sanger.ac.uk/pub4/resources/software/smalt/smalt-manual-0.7.4.pdf)

####Bio::Tradis::TradisPlot

• Required parameters:
  • mappedfile - mapped and sorted BAM file
• Optional parameters:
  • outfile - base name to assign to the resulting insertion site plot. Default = tradis.plot
  • mapping_score - cutoff value for mapping score. Default = 30
• Methods:
  • plot - create insertion site plots for reads in mappedfile. This file will be readable by the Artemis genome browser (http://www.sanger.ac.uk/resources/software/artemis/)

####Bio::Tradis::RunTradis

• Required parameters:
  • fastqfile - file containing a list of fastqs (gzipped or raw) to run the complete analysis on. This includes all (including intermediary format conversion and sorting) steps starting from filtering and, finally, producing an insertion site plot and a statistical summary of the analysis.
  • tag - TraDIS tag to filter for and then remove
  • reference - path to/name of reference genome in fasta format (.fa)
• Optional parameters:
  • mismatch - number of mismatches to allow when filtering/removing the tag. Default = 0
  • tagdirection - direction of the tag, 5' or 3'. Default = 3
  • mapping_score - cutoff value for mapping score. Default = 30
• Methods:
  • run_tradis - run complete analysis

Examples

Check whether file.bam contains TraDIS tag fields and, if so, adds the tags to the reads' sequence and quality strings.

my $detector = Bio::Tradis::DetectTags(bamfile => 'file.bam');
if($detector->tags_present){
	Bio::Tradis::AddTagsToSeq(bamfile => 'file.bam', outfile => 'tradis.bam')->add_tags_to_seq;
}

Filter a FastQ file with TraDIS tags attached for those matching the given tag. Then, remove the same tag from the start of all sequences in preparation for mapping.

Bio::Tradis::FilterTags(
	fastqfile => 'tradis.fastq',
	tag => 'TAAGAGTGAC', 
	outfile => 'filtered.fastq'
)->filter_tags;
Bio::Tradis::RemoveTags(
	fastqfile => 'filtered.fastq',
	tag => 'TAAGAGTGAC', 
	outfile => 'notags.fastq'
)->remove_tags;

Create mapping object, index the given reference file and then map the fastq file to the reference. This will produce index files for the reference and a mapped SAM file named tradis_mapped.sam.

my $mapping = Bio::Tradis::Map(
	fastqfile => 'notags.fastq', 
	reference => 'path/to/reference.fa', 
	outfile => 'tradis_mapped.sam'
);
$mapping->index_ref;
$mapping->do_mapping;

Generate insertion site plot for only reads with a mapping score >= 50

Bio::Tradis::TradisPlot(mappedfile => 'mapped.bam', mapping_score => 50)->plot;

Run complete analysis on fastq files listed in file.list. This includes filtering and removing the tags allowing one mismatch to the given tag, mapping, BAM sorting and creation of an insertion site plot and stats file for each file listed in file.list.

Bio::Tradis::RunTradis(
	fastqfile => 'file.list', 
	tag => 'GTTGAGGCCA', 
	reference => 'path/to/reference.fa', 
	mismatch => 1
)->run_tradis;

Scripts

Executable scripts to carry out most of the listed functions are available in the bin:

• check_tradis_tags - Prints 1 if tags are present, prints 0 if not.
• add_tradis_tags - Generates a BAM file with tags added to read strings.
• filter_tradis_tags - Create a fastq file containing reads that match the supplied tag
• remove_tradis_tags - Creates a fastq file containing reads with the supplied tag removed from the sequences
• tradis_plot - Creates an gzipped insertion site plot
• bacteria_tradis - Runs complete analysis, starting with a fastq file and produces mapped BAM files and plot files for each file in the given file list and a statistical summary of all files.

A help menu for each script can be accessed by running the script with no parameters