Sequencing quality question.

[JQL]

Hi,

I’m analyzing a metagenomics data set and am a bit concerned about the sequencing quality. It was run using NextSeq for PE150. I need a second opinion. Attached is Mothur's summary.seqs output from one of the samples, Sample10 as an example.

For the raw reads, the max read length is 151, the median is 129.
After assembly (stitch R1/R2 together, max is 292, median is 121.

Almost all the samples are like that more or less. Is this normal or is it an indication of poor seq quality?

thanks!

[SNPsaurus]

It looks like the library fragment length was short, so that many reads have an adapter trimmed off and (I imagine) many of the read 2s completely overlap the R1. What did the library fragment size distribution look like? Do you have trim stats? Or quality stats from the run?

[nucacidhunter]

As SNPsaurus has mentioned it is more likely library prep issue. Posting FastQC output for raw data would be more informative.