Table 2.

Susceptibility of S. meliloti efflux pump gene deletion strains to antimicrobial compounds

Straina	Relevant genotype	MIC (μg/ml)b
		ERM	TET	CAM	NAL	RIF	NEO	KAM	NOV	VAN	PXB	ACR	CV	SDS	DOC	Gen	p-CA	Nar	Ber	Lut	Chr
1021	Wild type	100	0.39	12.5	200	3.13	6.25	50	>100	50	1.56	100	400	400	>800	100	400	200	1,600	>50	>25
SE122	ΔsmeAB	1.56	0.1	6.25	100	1.56	6.25	50	>100	50	1.56	50	400	200	>800	50	400	100	400	50	25
SE536	ΔsmeAB smeAB+	100	50c	12.5	200	6.25	6.25	50	>100	50	1.56	200	400	400	>800	100	400	200	1,600	>50	>25
SE404	ΔsmeAB ΔsmeCD	1.56	0.1	3.13	50	1.56	6.25	50	>100	50	1.56	50	400	200	>800	50	400	100	400	50	25
SE272	ΔsmeAB ΔsmeEF	0.78	0.05	6.25	100	1.56	6.25	50	>100	50	1.56	50	400	200	>800	50	400	100	400	50	25
SE569	ΔsmeAB ΔsmeCD ΔsmeEF	0.78	0.05	3.13	50	1.56	6.25	50	>100	50	1.56	50	400	200	>800	50	400	100	400	50	25
SE424	ΔtolC	0.2	0.03	0.78	12.5	0.78	1.56	12.5	0.39	12.5	0.39	3.13	3.13	6.25	25	6.25	200	25	50	12.5	6.25
SE466	ΔsmeR	>100	1.56	25	400	12.5	6.25	50	>100	50	1.56	400	400	400	>800	200	400	>200	3,200	>50	>25

^aOnly strains that showed a change in sensitivity are shown.

^bMIC determination was performed at least three times. For single mutants, values in boldface differ from the 1021 (wild-type) control strain value by ≥2-fold. For double and triple mutants, values in boldface differ from the SE122 (ΔsmeAB) control strain value by ≥2-fold. Abbreviations: ERM, erythromycin; TET, tetracycline; CAM, chloramphenicol; NAL, nalidixic acid; RIF, rifampin; NEO, neomycin; KAM, kanamycin; NOV, novobiocin; VAN, vancomycin; PXB, polymyxin B; ACR, acriflavine; CV, crystal violet; SDS, sodium dodecyl sulfate; DOC, deoxycholate; Gen, genistein; p-CA, p-coumaric acid; Nar, naringenin; Ber, berberine; Lut, luteolin; Chr, chrysin.

^cTetracycline resistance was conferred by the antibiotic resistance marker.