Table 2.

Distinct GUS enzymes architectures and cellular localization.

Phylum (GUS Abundance %)	GUS Loop Classification	Localization	References
Bacteroidetes (52%)	L2	Transported across the inner microbial membrane	[31,38,39]
	mL1	Periplasmic space
	mL2	Transported across the inner microbial membrane
	NL	Periplasmic space
	rare mL1,2	Transported across the inner microbial membrane
Firmicutes (41%)	L1	Intracellular	[31,38,39]
	L2	Transported across the inner microbial membrane
	NL	Periplasmic space
	mL1	Periplasmic space
Verrucomicrobia (1.5%)	mL2	Transported across the inner microbial membrane	[31,38,39]
Proteobacteria (4%)	L1	Intracellular	[31,38,39]

NL: No Loop < 10 residues in Loop 1 region; <9 residues in Loop 2 region. Loop 1 (L1) > 15 residue in Loop 1 region of EcGUS; <9 residues in Loop 2 region. Mini-loop 1 (mL1) contains a loop of 10–15 residues in Loop 1 region; <9 residues in Loop 2 region. Loop 2 (L2) < 10 residue in Loop 1 region; >12 residues in Loop 2 region. Mini-loop 2 (mL2) < 10 residues in Loop 1 region; >9 and <12 residues in Loop 2 region. Mini-loop 1,2 (mL1,2) contain a loop of 10–15 residues in Loop 1 region; >9 and <12 residues in Loop 2 region.