The aerobic electron transport system of Eikenella corrodens

• Published in: Canadian journal of microbiology Vol. 48; no. 10; p. 895
• Main Authors: Jaramillo, Rubén D, Barraza, Beatriz C, Polo, Alma, Sará, Martín, Contreras, Martha, Escamilla, J Edgardo
• Format: Journal Article
• Language: English
• Published: Canada 01-10-2002
• Subjects: Aerobiosis; Eikenella corrodens - metabolism; Eikenella corrodens - physiology; Electron Transport; Electron Transport Complex IV - chemistry; Electron Transport Complex IV - metabolism; Heme - chemistry; Kinetics; Membranes - metabolism; Oxidation-Reduction; Oxygen Consumption; Spectrophotometry; Tetramethylphenylenediamine - metabolism
• DOI: 10.1139/w02-084
• ISSN: 0008-4166

The respiratory system of the fastidious beta-proteobacterium Eikenella corrodens grown with limited oxygen was studied. Membranes showed the highest oxidase activity with ascorbate plus N,N,N',N'-tetramethyl-p-phenylenediamine (TMPD) or succinate and the lowest activity with NADH and formate. The presence of a bc1-type complex was suggested by the inhibition exerted by 2-heptyl-4-hydroxyquinoline-N-oxide (HOQNO), myxothiazol, and antimycin A on respiration with succinate and by the effect of the latter two inhibitors on the succinate-reduced difference spectra. Respiration with succinate or ascorbate-TMPD was abolished by low KCN concentrations, suggesting the presence of a KCN-sensitive terminal oxidase. Cytochromes b and c were spectroscopically detected after reduction with physiological or artificial electron donors, whereas type a and d cytochromes were not detected. The CO difference spectrum of membranes reduced by dithionite and its photodissociation spectrum (77 K) suggested the presence of a single CO compound that had the spectral features of a cytochrome o-like pigment. High-pressure liquid chromatography analysis of membrane haems confirmed the presence of haem B; in contrast, haems A and O were not detected. Peroxidase staining of membrane type c cytochromes using SDS-PAGE revealed the presence of five bands with apparent molecular masses of 44, 33, 30, 26, and 14 kDa. Based on our results, a tentative scheme of the respiratory chain in E. corrodens, comprising (i) dehydrogenases for succinate, NADH, and formate, (ii) a ubiquinone, (iii) a cytochrome bc1, and (iv) a type-cbb' cytochrome c oxidase, is proposed.