trimming sequence portions

I am looking for a command in mothur that can do following task for me


I have a FASTA file (unaligned) that has suppose 1000 seq. All sequences areof varying length say some are 200 bp but some are even 850 bp. I know that anything that is beyond 550 bp is just noise because my primer set does not amplify 550 bp product at all in first place. so I want to kill portion of sequences that are beyond 550 bp because it is just noise. But I want to retain remaining front portion of sequence. So if some seq are more than 550 bp in my data file, I still want to retain them but only up to 550 bp in length.

Is this something that MOTHUR can do?

Please let me know
Thanks

See the chop.seqs command - http://www.mothur.org/wiki/Chop.seqs

Dr Schloss
Thanks for your reply. I used chop.seqs command, but I do not want what chop.seq command is doing.
I used following command

mothur > chop.seqs(fasta=total.fasta, numbases=100, keep=front)

In my total.txt file there were 7900 seq, when I used above command mothur returned me 7900 seq and all were 100 bp long. That means it trimmed everything down to 100 bp. This is not what I was looking for.
I wanted mothur to kill only sequence portions that exceeds beyond a certain length say 550 bp and retain the remaining portion.
So I want a script that can delete sequence bases if they are exceeding beyond a certain length say 550 bp in my case.

for example

I have such sequences in my data set. I want to keep this seq but not beyond 550 bp. so i want mothur to look for such seq and trim them to 550 bp.

GM0VFN301BWBUZ rank=0254869 x=661.0 y=633.0 length=839
GTAGTCCACGCCGTAAACGATGTCAACTAGCCGTTG
GAATCCTTGAGATCTTAGTGGCGCAGCTAACGCATT
AAGTTGACCGCCTGGGGAGTACGGCCGCAAGGTTAA
AACTCAAATGAATTGACGGGGGCCCGCACAAGCGGT
GGAGCATGTGGTTTAATTCGAAGCAACGCGAAGAAC
CTTACCAGGCCTTGACATCCAAGTGAACTTCCAGAG
ATGGTTAGTGCTCGGTACGACTGAGTACGAAGGTCG
ACGTGCCTAGTCGGACTTGGGTCCGTTCGACGGTCC
TACGGTCGTTCCGGTTGGTACGTAGTGGTTAGGGTT
AAGTTTCCCGGGTTAAACGTCCGGTAACCCCGAACC
CGTTCCGTTAACCCCTTTAGGTTACCCCTTAAGGTA
CCCAACGGTTTACGTACGGGTTTAGGGTCCGTAACG
GTTCCCTAAAAGGGTACGTAAACGTACGGGTCCCGG
TTAGGAACCCGGTAAAACCGGGGACGGAAAAACCGG
GGTTGGGGGAAAGTTGGGGAAACGTTCGAAACGGTT
CCAAAGTTCAACTTCGGGACCCTTTACCGGGCCCCT
TTACGGGGCCCTTAACGGACCGTTAACCGGTACGAC
CGTTAACGAACGTTACGGTAACCGGGTTAACGGTAC
GGGTAACGGGTTAGGACCCGGTTAAAGGGCCCCCGA
AACGGGACCGGGGTTCCGGGAAAAGGGTCCCGTAAA
AGTTCCCCCGTAAAAGGTAAAAACCCCCGGAAAGGT
AAAACCCCGGGTTTAGTTAACCCCGGGTAAGTTACC
CCCGGGGTACTAAACCGGGTTACCCTTA

There will be a short option in chop.seqs for the next release which will hopefully be out by the end of next week. Give it a whack and let us know what you think.

Thanks Dr Schloss