TABLE 1.

NPN uptake of C. testosteroni TK102 after cells were washed with several buffers^a

Buffer	Mean ± SD NPN fluorescence	NPN uptake factor
Control (NPN only)	0
PBS	143 ± 10	1
Tris-EDTA	261 ± 16	1.8
HEPES	300 ± 19	2.1

^aFluorescence was measured 2 min after the addition of 10 μM NPN to cells resuspended in PBS (pH 7.2). Fluorescence results are expressed in arbitrary units. Background fluorescence in the presence of NPN only (56 arbitrary units) was subtracted. The NPN uptake factor represents the ratio of each fluorescence value to the value obtained with PBS.