Abstract

Azomonas agilis PY101 produced a fluorescent yellow-green pigment promoted by cadmium. The amount of extracellular pigment produced during the growth of A. agilis PY101 increased to approximately 6 times its initial value after the addition to 1.0 mg/ml of CdCl_2. The pigment peak(peak II) was observed when the supernatant solution acquired from the cells cultivated in the presence of cadmium was fractionated on a column of Superdex 75. Peak II contained about 70% of extracellular cadmium in the supernatant solution. This cadmium-binding pigment contained several sulfur-containing groups. The dramatic decrease (97%) of sulfate ion (SO_4^-2)concentration in the cytoplasm from 9.60 to 0.25 ㎍/ml during the growth of A. agilis PY101 under cadmium stress was confirmed by ion chromatography. Moreover, transmission electron microscopic analysis showed that Z. agilis PY101 actively accumulated cadmium in the interior of the cells. It appears that the cadmium adaptation of A. agilis PY101 is achieved by the microbial binding of the sulfur-containing pigment to cadmium.

• Keywords: Azomonas agilis PY101; cadmium-binding pigment; cadmium accumulation