TABLE 4.

HbpR mediated relative luciferase activities in the presence of different compounds

Compounda	Relative induction (%)b		Compound	Relative induction (%)
Biphenylic compounds
Biphenyl	3.4 ± 0.3
2-Hydroxybiphenyl	100 ± 16
3-Hydroxybiphenyl	4.4 ± 0.4
4-Hydroxybiphenyl	3.5 ± 0.3
2,3-Dihydroxybiphenyl	1.1 ± 0.2
2,5-Dihydroxybiphenyl	0.21c ± 0.04
2,2′-Dihydroxybiphenyl	84 ± 12
4,4′-Dihydroxybiphenyl	2.0 ± 0.3
2-Aminobiphenyl	48 ± 7
2-Chlorobiphenyl	2.2 ± 0.2
Polycyclic aromatic hydrocarbons
Naphthalene	2.9 ± 0.3
1-Naphthol	2.4 ± 0.2
Monoaromatic hydrocarbons
Toluene	3.6 ± 0.5
Phenol	3.0 ± 0.4
2-Methylphenol	4.2 ± 0.4
2-Ethylphenol	3.7 ± 0.3
2-Propylphenol	3.8 ± 0.4
Salicylic acid	3.0 ± 0.3
Benzoic acid	3.3 ± 0.3
3-Methylcatechol	1.0 ± 0.2
2,3-Dihydroxybenzaldehyde	1.1 ± 0.1
2-Hydroxydiphenylmethane	32 ± 7
Backgroundd	3.0 ± 0.4

^aAssays were carried out with P. azelaica HBP104. Compounds were added to the assay as 100-fold-concentrated DMSO stock solutions to obtain a final concentration of 0.2 mM. 

^bLuciferase activities were measured after 2 h 15 min and were related to the 2-hydroxybiphenyl-induced light emission of 3.71 × 10⁴ relative light units, which was arbitrarily set to 100%. The values reported here were obtained in two independent experiments, both performed in triplicate. Boldface numbers indicate significant induction compared to background. 

^cThe culture turned violet during the assay. 

^dBackground luciferase activity was determined by adding only DMSO instead of inducer stock solution to an assay mixture.