MOTHUR command "chimera.vsearch"

Question

[dpc]

Hi there!!! Can you please explain how MOTHUR finds the chimeric sequence from a "fasta" file when used with "count_table" file. command:

mothur > chimera.vsearch(fasta=stool.trim.unique.good.align, count=stool.trim.good.count_table)

I mean how is it possible to find the chimeric sequence without a reference. Just want to know what is the procedure that runs at the "back end"

Thank You