Mechanism of cyanide and thiocyanate decomposition by an association of Pseudomonas putida and Pseudomonas stutzeri strains

The intermediate and terminal products of cyanide and thiocyanate decomposition by individual strains of the genus Pseudomonas, P. putida strain 21 and P. stutzeri strain 18, and by their association were analyzed. The activity of the enzymes of nitrogen and sulfur metabolism in these strains was compared with that of the collection strains P. putida VKM B-2187^T and P. stutzeri VKM B-975^T. Upon the introduction of CN^? and SCN^? into cell suspensions of strains 18 and 21 in phosphate buffer (pH 8.8), the production of NH ₄ ⁺ was observed. Due to the high rate of their utilization, NH₃, NH ₄ ⁺ , and CNO^? were absent from the culture liquids of P. putida strain 21 and P. stutzeri strain 18 grown with CN^? or SCN^?. Both Pseudomonas strains decomposed SCN^? via cyanate production. The cyanase activity was 0.75 µmol/(min mg protein) for P. putida strain 21 and 1.26 μmol/(min mg protein) for P. stutzeri strain 18. The cyanase activity was present in the cells grown with SCN^? but absent in cells grown with NH ₄ ⁺ . Strain 21 of P. putida was a more active CN^? decomposer than strain 18 of P. stutzeri. Ammonium and CO₂ were the terminal nitrogen and carbon products of CN^? and SCN^? decomposition. The terminal sulfur products of SCN^? decomposition by P. stutzeri strain 18 and P. putida strain 21 were thiosulfate and tetrathionate, respectively. The strains utilized the toxic compounds in the anabolism only, as sources of nitrogen (CN^? and SCN^?) and sulfur (SCN^?). The pathway of thiocyanate decomposition by the association of bacteria of the genus Pseudomonas is proposed based on the results obtained.