Question: Analyzing only forward reads in mothur
gravatar for giderk
18 months ago by
giderk0 wrote:

I am new to using mothur and in attempting to follow the MiSeq_SOP guide with my data on 18S rRNA v4 sequences I am stumped in the beginning. The guide assumes you want to make contigs from paired-end reads, but I would like to analyze my forward reads separately. How do I combine just my read 1 fastq files, retaining the sample name for all the sequences in each file of course, so that I can proceed with the following alignment and classification steps? I can't seem to find an explanation on how to do this anywhere.

forward read miseq mothur • 1.3k views
ADD COMMENTlink modified 10 months ago by alealdre10 • written 18 months ago by giderk0

I have a similar question. Any luck in finding a solution?

ADD REPLYlink written 14 months ago by pmatson0

Can't you just skip the make.contigs()? Try preparing the stability files with just R1.

You may also have to hack your way and change your file names to the same pattern Mothur uses after the make.contigs() step.

ADD REPLYlink written 14 months ago by h.mon15k

But make.contigs() is the step where a quality information filter is applied as fastq files are converted to fasta files. If you skip make.contigs how do you get a fasta file? I tried making a .files table with only the forward fastq listed but wasn't able to get it to work. If you did, could you please share an example of the format?

Thanks! I am having this same problem trying to re-analyze some old public datasets (sequenced before paired end was a thing.)

Here is the description of the .files file format. You'll notice every format option includes a forward and reverse read:

ADD REPLYlink modified 14 months ago • written 14 months ago by rrr40
gravatar for alealdre
10 months ago by
alealdre10 wrote:

Hey there, you could use to obtain the fasta and quality file for either forward or reverse sequences. Here is the link to the mothur help:

Hope it's what you needed!

ADD COMMENTlink written 10 months ago by alealdre10

That's what I did. I wanted to test the pipeline on paired ends and on forward and reverse separately, so I used to obtain a fasta file from the fastq. I think make.contigs() also outputs a .groups file which is not made when you use, so you need to make a .groups file too as you need that for unique.seqs()...

ADD REPLYlink written 9 months ago by vali0
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