See also
Annotations
fastx_strip_annots command
Re-labels sequences in a FASTA or FASTQ file. By default, the new labels are Seq1, Seq2, Seq3 etc. The prefix can be changed using the ‑prefix option.
Existing annotations are removed from the labels unless the -keep_annots option is specified.
The output filename is specified by -fastqout (FASTQ format) and / or -fastaout (FASTA format). You cannot create FASTQ output from FASTA input.
Example
usearch -fastx_relabel otus.fa -prefix Otu -fastaout relabeled.fa
-keep_annots