Cyanide production by Pseudomonas fluorescens and Pseudomonas aeruginosa

Of 200 water isolates screened, five strains of Pseudomonas fluorescens and one strain of Pseudomonas aeruginosa were cyanogenic. Maximum cyanogenesis by two strains of P. fluorescens in a defined growth medium occurred at 25 to 30 degrees C over a pH range of 6.6 to 8.9. Cyanide production per cell was optimum at 300 mM phosphate. A linear relationship was observed between cyanogenesis and the log of iron concentration over a range of 3 to 300 microM. The maximum rate of cyanide production occurred during the transition from exponential to stationary growth phase. Radioactive tracer experiments with [1-14C]glycine and [2-14C]glycine demonstrated that the cyanide carbon originates from the number 2 carbon of glycine for both P. fluorescens and P. aeruginosa. Cyanide production was not observed in raw industrial wastewater or in sterile wastewater inoculated with pure cultures of cyanogenic Pseudomonas strains. Cyanide was produced when wastewater was amended by the addition of components of the defined growth medium.