(A) SSN of the HMP GUSome with putative FMN-binders as larger, outlined circles and those that were synthesized and characterized further are labeled. BLAST/e-value/cut off value utilized to generate this SSN is 10−220 and sequences were acquired from the HMP stool sample database. (B) Genome neighborhood diagrams of putative FMN-binding GUSs (C) Absorbance scans of purified Rh2GUS, Rg3GUS, BvGUS, and RiGUS reveal flavin binding profile. (D) Mass spectra of purified Rh2GUS, Rg3GUS, BvGUS, and RiGUS reveal mass for FMN.