Table 3.

Substrates of Biolog GN2 microplates with distinct differences in activities between clinical and environmental isolates

GN2 plate substrate	Respiration of E. coli O157:H7 isolatesa
	Spinach RM6067	Environmental				Spinach clinical
		RM6101	RM6102	RM6103	RM6149	RM9998	RM6069
Dextrin	178	111	150	173	108	283	275
l-Rhamnose	61	20	48	92	23	197	192
Methyl pyruvate	204	198	211	282	162	416	477
Mono-methylsuccinate	176	217	242	226	134	486	442
d-Glucuronic acid	241	350	381	394	310	585	520
d,l-Lactic acid	152	159	197	367	192	539	433
Succinic acid	209	206	288	251	200	413	395
d-Alanine	6	3	7	190	7	318	214
l-Alanine	82	94	115	262	103	401	330
l-Alanyl-glycine	49	21	72	114	62	292	227
Glycyl-l-aspartic acid	51	17	22	42	21	251	265
l-Serine	93	14	40	48	21	333	465
l-Threonine	13	13	25	20	14	115	125
Glycerol	185	143	243	241	152	458	433
d,l-α-Glycerolphosphate	147	134	199	219	119	443	449

^aValues are a unitless measure of respiration based on the reduction of tetrazolium dye. Values are optical density units reflecting color formation due to oxidation of the compounds by bacterial cells. Optical density for each substrate was normalized to that in control wells (no substrate).