Confusing quality plot

[Zubidiego (Diego Zubillaga)]

Hello everyone!
I am starting to work with a set of 155 samples of V4 region of 16s rRNA that was sequenced using Illumina. I impoted all my data and reached the quality scores plot using QIIME2 2023.5 in conda, but it seems that the sequences are a little weird. I have samples that go from 8784 to 2691122. What do you think abour this? It could be a problem with sequencing or with the creation of the libraries? I am worried because its all the work for my masters degree. Can i keep wprking with this?

Thanks a lot!

Diego

[colinvwood (Colin Wood)]

Hello @Zubidiego,

Are you confused about the quality distributions, or the number of sequences assigned to samples?

[Zubidiego (Diego Zubillaga)]

I am confused about the quality distributions, i've never seen quality graphs like these ones.

[colinvwood (Colin Wood)]

Hello @Zubidiego,

I believe that these are referred to as binned quality scores and that newer illumina sequencers output them. You can search on this forum about the topic, there are a few discussions.