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Old 12-31-2009, 09:37 AM   #1
bre
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Default Building indexes with bowtie-build

Hello, I am currently trying to align two closely related genomes from multiple sequence fasta files. I have a target genome which is made of 1168 sequences in a single fasta file and I wish to use this to build indexes. Initially I did this with the command "bowtie-build target_file.fa t_index". This ran in a reasonable amount of time and produced 6 index files: t_index.1.ebwt, t_index.2.ebwt, t_index.3.ebwt, t_index.4.ebwt, t_index.rev.1.ebwt, t_index.rev.2.ebwt.
I then ran the command "bowtie t_index -f -t -p4 -l 13 ../PATH/TO/QUERY output.map" to run an alignment, where QUERY is also a multiple sequence fasta file where each sequence length is <= 1024 bases. My output was not what I was expecting; I got only 5.03% alignment when I was expecting over 90%. This lead my to wonder whether or not indexes had been created correctly. Is bowtie-build able to take a multisequence fasta file? Maybe each index file was being overwritten by each following sequence in the target file? I tweaked some parameters and was still not able to get over 6% alignment.
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Old 12-31-2009, 11:56 AM   #2
bre
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Default Self alignment

I tested the indexes by running them against the sequences they were created from and only got 67% alignment so this leads me to further doubt the indexes obtained. Has anyone else had similar problems?
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Old 01-01-2010, 09:56 PM   #3
Xi Wang
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I have successfully built the index from multiple sequences in a fasta file and the mapping results seem all right. I guess the problem you encountered is because of the length of the sequence you queried. Such kind of NGS mapping tools is mainly designed for short read alignment.
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Old 03-31-2010, 10:16 PM   #4
ZZQ
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I've heard of bowtie, but have not a try yet.
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Old 04-01-2010, 08:38 AM   #5
sperry
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For the read lengths you are working with, you are probably better off using a different alignment tool. BWA has an alignment option that specifically accommodates longer read lengths (bwasw). http://bio-bwa.sourceforge.net/

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Originally Posted by bre View Post
I tested the indexes by running them against the sequences they were created from and only got 67% alignment so this leads me to further doubt the indexes obtained. Has anyone else had similar problems?
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