Real-time detection of viable microorganisms by intracellular phototautomerism

BMC Biotechnology

Table 1 Selected probes for the RTV assay

code	name	exc. max. (nm)	em. max. (nm)	Stokes shift (nm)	pKf	pH ratio	uptake
							S. aur	S. cer
V1	salicylic acid	295	405	110	2.9	122	+	+
V2	4-amino salicylic acid (PAS)	295 (265)	400	105	2.2 (3.5)	22 (74)	+	-
V3	5-amino salicylic acid (mesalamine)	335	495	160	5.8	331	-	-
V4	5-hydroxy salicylic acid (gentisic acid)	322	448	126	2.9	77	+	-
V5	4-hydroxy salicylic acid (β-resorcylic acid)	290	395	105	3.0	52	+	-
V6	1-hydroxy-2-naphtoic acid	340	420	80	3.0	3	+	+
V7	3-amino-2-naphtoic acid	360 (285)	470	110	4.5	88 (42)	+	+
V8	2-hydroxycinnamic acid (o-coumaric acid)	320 (360)	500	180	5.5 (>9)	30 (400)	+	-
V9	2-Hydroxy-dibenzofuran-3-carboxylic acid	340 (300)	450	110	2.3	4.3 (3.7)	+	+
V10	6-Amino-1,3-dimethyl-2-oxo-2,3-dihydro-1H-benzoimidazole-5-carboxylic acid	241	396	155	nd	1.4*	-	+
V11	5-(2-Ethyl-butyrylamino)-2-hydroxy-benzoic acid	311	426	115	nd	22.8*	+	-
V12	2-Hydroxy-5-[(tetrahydro-furan-2-carbonyl)-amino]-benzoic acid	307	417	110	nd	17*	+	-
V13	7-Amino-2,3-dihydro-benzodioxine-6-carboxylic acid	323	401	78	nd	359*	+	-
V14	2-Hydroxy-5-tetrazol-1-yl-benzoic acid	296	395	99	nd	5*	+	-

Overview of fluorescent compounds used for real-time monitoring of cell viability. Abbreviations: exc. max., excitation maximum; em. max., emission maximum; S.aur, Staphyloccus aureus; S. cer, Saccharomyces cerevisiae. The ratio of emission intensity was monitored at pH 7.5 and 1 as well as at pH 7 and 2 (indicated by the asterisk). Uptake of compounds by viable S. aureus and S. cerevisiae cells was monitored in a Tecan microplate fluorometer at optimal excitation and emission wavelengths.

ISSN: 1472-6750