Enzymatic Characterization and In Vivo Function of Five Terminal Oxidases in Pseudomonas aeruginosa

• Published in: Journal of bacteriology Vol. 196; no. 24; pp. 4206 - 4215
• Main Authors: Arai, Hiroyuki, Kawakami, Takuro, Osamura, Tatsuya, Hirai, Takehiro, Sakai, Yoshiaki, Ishii, Masaharu
• Format: Journal Article
• Language: English
• Published: United States American Society for Microbiology 01.12.2014
• Subjects: Bacteria; Bacteriology; cell membranes; Cells; cytochrome-c oxidase; Electron transfer; Electron Transport; electron transport chain; Enzymes; Gene Expression Profiling; Gene Knockout Techniques; Kinetics; mutants; niches; Oxidoreductases - genetics; Oxidoreductases - metabolism; Oxygen; Oxygen - metabolism; pathogens; Pseudomonas aeruginosa; Pseudomonas aeruginosa - enzymology; Pseudomonas aeruginosa - genetics
• ISSN: 0021-9193; 1098-5530
• DOI: 10.1128/JB.02176-14

The ubiquitous opportunistic pathogen Pseudomonas aeruginosa has five aerobic terminal oxidases: bo3-type quinol oxidase (Cyo), cyanide-insensitive oxidase (CIO), aa3-type cytochrome c oxidase (aa3), and two cbb3-type cytochrome c oxidases (cbb3-1 and cbb3-2). These terminal oxidases are differentially regulated under various growth conditions and are thought to contribute to the survival of this microorganism in a wide variety of environmental niches. Here, we constructed multiple mutant strains of P. aeruginosa that express only one aerobic terminal oxidase to investigate the enzymatic characteristics and in vivo function of each enzyme. The Km values of Cyo, CIO, and aa3 for oxygen were similar and were 1 order of magnitude higher than those of cbb3-1 and cbb3-2, indicating that Cyo, CIO, and aa3 are low-affinity enzymes and that cbb3-1 and cbb3-2 are high-affinity enzymes. Although cbb3-1 and cbb3-2 exhibited different expression patterns in response to oxygen concentration, they had similar Km values for oxygen. Both cbb3-1 and cbb3-2 utilized cytochrome c4 as the main electron donor under normal growth conditions. The electron transport chains terminated by cbb3-1 and cbb3-2 generate a proton gradient across the cell membrane with similar efficiencies. The electron transport chain of aa3 had the highest proton translocation efficiency, whereas that of CIO had the lowest efficiency. The enzymatic properties of the terminal oxidases reported here are partially in agreement with their regulatory patterns and may explain the environmental adaptability and versatility of P. aeruginosa.