Is this sequence depth distribution normal?

[Victoria_Ruiz]

Hi Nick,

Quick question, I sequenced samples using V4 primers however the barcodes are now on the forward primer. I used Qiime 2 to demultiplex using the script

qiime demux emp-paired
--i-seqs 02_import_sequences/imported_seqs.qza
--m-barcodes-file 01_mapping_file/RP2_mapping_file_validated.txt
--m-barcodes-category BarcodeSequence
--o-per-sample-sequences 03_demultiplex/demux.qza.

When I look at the counts summary I have some samples that have a sequence depth in the 200,000 range while others are in the 7000 range the average depth of 7807 with a minimum of 31. This is my first time demultplexing using these new primers. Should I be concerned about the count summary. Did I do something wrong?

Thank you for your help.

Best,
Victoria

[colinbrislawn (Colin J Brislawn)]

Hello Victoria,

Unfortunately, yes. That's pretty normal. Here are two distributions from recent 16S and ITS data sets.

I guess we all hope for a flatter distribution where fewer samples fail, but

Colin