Simultaneous presence of two terminal oxidases in the respiratory system of dark aerobically grownRhodospirillum rubrum

✍ Scribed by Carmen Fenoll; Juan M. Ramírez

• Publisher: Springer
• Year: 1984
• Tongue: English
• Weight: 600 KB
• Volume: 137
• Category: Article
• ISSN: 0302-8933
• DOI: 10.1007/bf00425805

✦ Synopsis

Rhodospirillum rubrum CAF10, a spontaneous cytochrome oxidase defective mutant, was isolated from strain S 1 and used to analyze the aerobic respiratory system of this bacterium. In spite of its lack of cytochrome oxidase activity, strain CAFI0 grew aerobically in the dark although at a decreased rate and with a reduced final yield. Furthermore, aerobically grown mutant cells took up O2 at high rates and membranes isolated from those cells exhibited levels of NADH and succinate oxidase activities which were similar to those of wild type membranes. It was observed also that whereas in both strains 02 uptake (intact cells) and NADH and succinate oxidase activities (isolated membranes) were not affected by 0.2 mM KCN, the cytochrome oxidase activity of the wild type strain was inhibited about 90 % by 0.2 mM KCN. These data indicate the simultaneous presence of two terminal oxidases in the respiratory system of R. rubrum, a cytochrome oxidase and an alternate oxidase, and suggest that the rate of respiratory electron transfer is not limited at the level of the terminal oxidases. It was also found that the aerobic oxidation of cellular cytochrome c2 required the presence of a functional cytochrome oxidase activity. Therefore it seems that this electron carrier, which only had been shown to participate in photosynthetic electron transfer, is also a constituent of the respiratory cytochrome oxidase pathway.