FIG. 5.

Separation of different redox mediators from a culture supernatant of S. xenophaga AKE1. The culture supernatant (10 ml) was applied to a solid-phase extraction column (500 mg of Butyl C4 [Applied Separations]), which was preequilibrated with Na/K phosphate buffer (50 mM, pH 7.3). The fractions were eluted with steps consisting of Na/K phosphate buffer (2 ml), water (2 ml), 20% (vol/vol) methanol (0.8 ml), 50% (vol/vol) methanol (0.6 ml), 75% (vol/vol) methanol (0.6 ml), and 100% (vol/vol) methanol (1 ml). Fractions (150 μl) were collected, and the absorbance at 460 nm was determined (bars) by using a microtiter plate spectrophotometer. Aliquots (20 μl) of each fraction were tested with resting cells of strain BN6 in the standard microtiter plate assay under anaerobic conditions for the decolorization of amaranth (▴). The fraction (fraction 24) which was subsequently analyzed is indicated by an arrow.