Abstract
When hexavalent chromium (Cr6+) tolerant Pseudomonas ambigua G-l was cultivated in nutrient broth containing 150 ppm Cr6 +, the Cr6+ content of the broth rapidly decreased. The Cr6+ reducing enzyme found in a cell-free extract of P. ambigua G-l required NADH but not NADPH as a hydrogen donor for the reduction of Cr6 +. The specific activities of cell-free extracts of several Cr6+ sensitive mutants derived from P. ambigua G-l showed decreases to one fourth to one tenth of that of P. ambigua G-l. Glucose protected the Cr6+ reducing enzyme against inac-tivation on dialysis.