Making an OTU table (otutab command)
Merge two or more OTU tables by matching sample identifiers and / or OTU identifiers. The input file must be in QIIME classic format.
The input files are specified as a comma-separated list immediately following -otutab_merge. Spaces are not allowed in file names.
The output file is specified by the -output option. The output file is also in QIIME classic format.
usearch -otutab_merge otutable1.txt,otutable2.txt,otutable3.txt -output otutable_merged.txt