Parsing header of FASTA File

I have so many bacterial Refseq fasta files and want to parse the headers in the fasta files to see if is there any word 'chromosome' in the headers, as a side note there are some sequences in FASTA files started with '>' so i want to parse all the lines staring with '>' . I know i have files that do not have word like 'chromosome' . I would like to separate the files with header 'chromosome' from the rest of files. Is there a way to do so?

any help would be appreciated.

fasta sequence header parse

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updated 7.9 years ago by ATpoint

• written 7.9 years ago by Shelle •

If you want to get faster/better/more accurate answers it would really help if you show some examples of your data, and how these have to be "parsed".

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written 7.9 years ago by WouterDeCoster

I’m not sure what the aim of filtering the genomes is by the word chromosome is exactly?

To my knowledge the work chromosome in the header doesn’t tell you anything about that assembly specifically.

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written 7.9 years ago by Joe

Assuming that fasta is linearized (i.e sequence is in single line, after header):

sed -n '/>/p' test.fa | grep -vw chromosome | grep --no-group-separator -f - -A 1 test.fa

should give you all the fasta sequences with no chromosome in header.

sed -n '/>/p' test.fa | grep -w chromosome | grep --no-group-separator -f - -A 1 test.fa

should give you all the fasta sequences with chromosome in header.

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written 7.9 years ago by cpad0112

1 answer

You can do it with this one-liner:

grep '>chromosome' *.fasta | awk -F ":" '{print $1}' | tee haveChr.txt | diff /dev/stdin <(ls *.fasta) | awk -F "> " '{print $2}' | awk NF > haveNOChr.txt

By the way, fasta headers must start with '>'. Do you have some that do not start with it?

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written 7.9 years ago by ATpoint

I tried this command and all the files go to haveNoChr.txt which is not correct as i have files with header (first line) as below: A few examples is as follows:

>NZ_LS483492.1 Serratia rubidaea strain NCTC10848 genome assembly, chromosome: 1
>NC_013791.2 Bacillus pseudofirmus OF4, complete genome  
>NZ_CP016324.1 Vibrio cholerae 2740-80 chromosome 1, complete sequence

I have gone through the whole file in second example and i didn't see any line starting with '>' which includes 'chromosome'. I am not sure why this one-liner doesn't separate at least this file in a haveNOchr.txt

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written 7.9 years ago by Shelle •

Ok, I see. In this case, simply grep for 'chromosome' instead of '>chromosome'.:

grep 'chromosome' *.fasta | awk -F ":" '{print $1}' | tee haveChr.txt | diff /dev/stdin <(ls *.fasta) | awk -F "> " '{print $2}' | awk NF > haveNOChr.txt

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written 7.9 years ago by ATpoint

Did it work for you @Shelle ?

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written 7.9 years ago by ATpoint