FIG. 1.

Reduction of amaranth (A) or Mordant yellow 3 (B) under anaerobic conditions by whole cells of Sphingomonas sp. strain BN6 (●) or BN6(pRJR34) (■). The cells were grown aerobically in a mineral medium with glucose (10 mM) and naphthalene-2-sulfonate (0.5 mM) [plus 10 μg of tetracycline per ml for BN6(pRJR34)]. When the cells reached the late-exponential growth phase, 25 ml of the cultures was transferred into serum bottles (100-ml volume) with a nitrogen atmosphere, and glucose (10 mM) and Mordant yellow 3 (1 mM) or amaranth (1.3 mM) were added. At the indicated intervals, aliquots were taken, cells were removed by centrifugation, and the concentrations of the azo dyes were determined by high-performance liquid chromatography.