TABLE 5.

yheI biomarker-inducing compounds identified in screening of 14,000 natural products, compared to some noninducing protein biosynthesis inhibitors

Compound	Structural class	Ribosomal subunit specificity	Signal (%) at concna (μg/ml) of:
			12.5	6.25	3.13	1.56
yheI biomarker-inducing compounds
Chloramphenicol		50S	140	440	840	570
Tylosinb	16-Membered macrolide	50S	880	490	340	200
Viridogriseinb	Streptogramin B type	50S	180	430	520	110
Pristinamycin 1Cb	Streptogramin B type	50S	10	20	160	470
Mikamycin A	= Streptogramin A	50S	150	350	520	350
Sparsomycin		50S	240	180	150	120
Thiostrepton	Thiopeptide	50S	380	190	160	110
Thiopeptin B	Thiopeptide	50S	210	130	110	100
A10255J	Thiopeptide	EF-Tu?c	20	20	90	200
Althiomycin		50S	360	270	230	200
Cephalosporin P1	Steroid	EF-G	10	30	190	290
Helvolic acid	Steroid	EF-G	250	170	140	120
Bamicetin	Amicetin-type nucleoside	50S	370	250	190	150
Amicetin	Amicetin-type nucleoside	50S	330	190	270	130
Pleuromutilin		50S	200	340	110	230
Hygromycin A		50S	240	160	170	140
Oxytetracycline	Tetracycline	30S (50S)	20	100	440	480
Ferrimycin A1d	Sideromycin	Unknown	20	30	440	770
Trinactine	Polynactin		650	210	190	130
Noninducing protein biosynthesis inhibitors of the natural product library
Actinoninf			120	80	85	90
Streptomycing	Aminoglycoside	30S	88	89	100	95
Puromycin	Aminoacyl-adenosine analogue		50	80	101	110
Fusidic acidh	Steroid	EF-G	20	20	20	20
Siomycin Ah	Thiopeptide	50S	20	20	20	30

^aLuminescence data measured during hit confirmation at four different compound concentrations between 1.56 and 12.5 μg/ml. Values represent percentages of the noninduced biomarker signal. In a case where a value is above 200% (bold numbers), the biomarker system is considered to be induced. Underlined values (below 50%) indicate antibiotic effects during cell incubation.

^bThree screening hits represented tylosins, and three additional ones were viridogriseins. Due to a plasmid-encoded resistance determinant in the biosensor cell, yheI marker induction by 14-membered macrolides, such as erythromycin, by lincomycin, or by streptogramin B cannot be expected. Nevertheless, close congeners of streptomycin B do indeed induce the biomarker.

^cA related compound (GE2270A) binds to EF-Tu.

^dFerrimycin consists of a siderophore carrier and a probable bioactive moiety. Only limited data are available concerning its antibiotic MOA. yheI marker induction indicates that ferrimycin might indeed inhibit protein biosynthesis.

^eTrinactin is known to interfere with biomembranes by acting as an ionophore.

^fActinonin inhibits the peptide deformylase, an essential enzyme involved in the posttranslational processing of proteins.

^gBesides streptomycin, the aminoglycosides gentamicin, kanamycin, and neomycin also do not induce the yheI biomarker. Only spectinomycin, which in contrast to the other aminoglycosides does not cause misreading during translation, induces the biomarker at high concentrations (25 μM).

^hFusidic acid and siomycin A are indeed inducing agents below 1.56 μg/ml. At screening concentrations above 1.56 μg/ml, they already inhibit bacterial growth and repress the luciferase signal.