I am a little bit confused about chimeric sequences removal in qiime1 and qiime2.
In qiime1 we remove chimeric sequences after assign taxonomy using identify_chimeric_seqs.py script whereas I can able to understand that in qiime2, dada2 remove chimeric by default.
Hi @Yogesh_Gupta,
There is not really any reason to remove chimera after taxonomy assignment, it’s just a waste of computational resources to hold on to chimera that long — in qiime1 (to my knowledge) chimera removal was done either before or after OTU clustering.
Chimera removal happens at a similar time in QIIME 2: after OTU clustering or denoising. dada2 will remove chimera after denoising. If you use q2-vsearch for OTU clustering instead, you should use q2-vsearch for chimera removal.