Thank you for your response. and sorry for my unclear question.
I'm using qiime2 V 2021.2 on virtual machine.
I used this command to remove the primers:
qiime cutadapt trim-paired \
-- i- *demultiplexed-sequences paired-end-demux.qza *
--p-front-f CCTACGGGNGGCWGCAG **
--p-front-r GACTACHVGGGTATCTAATCC **
but nothing has been done for adapters if it is necessary to do.
and then used this comma qiime dada2 denoise-paired **
--p-trim-left-f 0 \
--p-trim-left-r 0 \
--p-trunc-len-f 232 \
--p-trunc-len-r 232 \
--o-table table.qza \
--o-representative-sequences rep-seqs.qza \
exactly the chimeric sequences concern me. since some one else got the below result:
I'm not sure what can be the difference in our commands which concluded different results. I cannot access that person to ask him about the command he run
the primers and adapters are as below:
The forward primer was constructed with the Illumina 5' overhang adapter sequence (TCGTCGGCAGCGTCAGATGTGTATAAGAGACAG) followed by the forward primer sequence (CCTACGGGNGGCWGCAG). The reverse primer was constructed with another 5' overhang adapter sequence (GTCTCGTGGGCTCGGAGATGTGTATAAGAGACAG) and followed by the reverse primer sequence (GACTACHVGGGTATCTAATCC).
thank you very much in advance