Investigation of the physiological relationship between the cyanide-insensitive oxidase and cyanide production in Pseudomonas aeruginosa.
Pseudomonas aeruginosa is an opportunistic pathogen which demonstrates considerable respiratory versatility, possessing up to five terminal oxidases. One oxidase, the cyanide-insensitive oxidase (CIO), has been previously shown to be resistant to the potent respiratory inhibitor cyanide, a toxin that is synthesized by this bacterium. This study investigated the physiological relationship between hydrogen cyanide production and the CIO. It was found that cyanide is produced in P. aeruginosa at similar levels irrespective of its complement of CIO, indicating that the CIO is not an obligatory electron sink for cyanide synthesis. However, MICs for cyanide and growth in its presence demonstrated that the CIO provides P. aeruginosa with protection against the effects of exogenous cyanide. Nevertheless, the presence of cyanide did not affect the viability of cio mutant strains compared to the wild-type during prolonged incubation in stationary phase. The detection of the fermentation end products acetate and succinate in stationary-phase culture supernatants suggests that P. aeruginosa, irrespective of its CIO complement, may in part rely upon fermentation for energy generation in stationary phase. Furthermore, the decrease in cyanide levels during incubation in sealed flasks suggested that active breakdown of HCN by the culture was taking place. To investigate the possibility that the CIO may play a role in pathogenicity, wild-type and cio mutant strains were tested in the paralytic killing model of Caenorhabditis elegans, a model in which cyanide is the principal toxic agent leading to nematode death. The CIO mutant had delayed killing kinetics, demonstrating that the CIO is required for full pathogenicity of P. aeruginosa in this animal model.
Zlosnik
James E A
JEA
Division of Biology, Faculty of Natural Sciences, Imperial College London, Sir Alexander Fleming Building, London SW7 2AZ, UK.
Tavankar
Gholam Reza
GR
Division of Biology, Faculty of Natural Sciences, Imperial College London, Sir Alexander Fleming Building, London SW7 2AZ, UK.
Bundy
Jacob G
JG
Division of Biomedical Sciences, Faculty of Natural Sciences, Imperial College London, Sir Alexander Fleming Building, London SW7 2AZ, UK.
Mossialos
Dimitris
D
Division of Biology, Faculty of Natural Sciences, Imperial College London, Sir Alexander Fleming Building, London SW7 2AZ, UK.
O'Toole
Ronan
R
Division of Biology, Faculty of Natural Sciences, Imperial College London, Sir Alexander Fleming Building, London SW7 2AZ, UK.
Williams
Huw D
HD
Division of Biology, Faculty of Natural Sciences, Imperial College London, Sir Alexander Fleming Building, London SW7 2AZ, UK.
D019342:Acetic Acid / Q000032:analysis; D000693:Anaerobiosis; D000818:Animals; D000900:Anti-Bacterial Agents / Q000378:metabolism / Q000633:toxicity; D017173:Caenorhabditis elegans / Q000382:microbiology; D015169:Colony Count, Microbial; D005285:Fermentation; D017353:Gene Deletion; D006856:Hydrogen Cyanide / Q000378:metabolism* / Q000633:toxicity; D008826:Microbial Sensitivity Tests; D050296:Microbial Viability; D023421:Models, Animal; D010088:Oxidoreductases / Q000235:genetics / Q000378:metabolism*; D011550:Pseudomonas aeruginosa / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism* / Q000472:pathogenicity; D019802:Succinic Acid / Q000032:analysis
D000900:Anti-Bacterial Agents; D006856:Hydrogen Cyanide; D019802:Succinic Acid; D010088:Oxidoreductases; C020094:duroquinol oxidase; D019342:Acetic Acid