Haem O and a putative cytochrome bo in a mutant of Bacillus cereus impaired in the synthesis of haem A
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© Springer-Verlag 1997
O R I G I N A L PA P E R
I. P. Del Arenal · M. L. Contreras · B. B. Svlateorova · P. Rangel · F. Lledías · J. R. Dávila · J. E. Escamilla
Haem O and a putative cytochrome bo in a mutant of Bacillus cereus impaired in the synthesis of haem A
Received: 21 June 1996 / Accepted: 9 October 1996
Abstract In a spontaneous mutant (PYM1) of Bacillus cereus impaired in the synthesis of haem A, no haem-Acontaining cytochromes were detected spectroscopically. The haem A deficiency was compensated by high levels of haem O and a CO-reactive cytochrome o in membranes; no other oxidases were detected. In contrast, the wild-type strain had considerable amounts of haem A and negligible levels of haem O. The mutant PYM1 exhibited normal colony morphology, growth, and sporulation in nonfermentable media, whereas on fermentable media, the mutant overproduced acid, which led to poor growth and inhibition of sporulation. External control of the pH of the medium in fermentable media allowed close-to-normal growth and massive sporulation of the mutant. The presence of membrane-bound cytochrome caa3-OII and aa3-II subunits in strain PYM1 was confirmed by Western blots and haem C staining (COII subunit). Western blotting also revealed that in contrast to the wild-type – strain PYM1 contained the membrane-bound subunits caa3-COI and aa3-I, but in low amounts. The effect of several respiratory inhibitors on the respiratory system of strain PYM1 suggested that the terminal oxidase is highly resistant to KCN and CO and that a c-type cytochrome might be involved in the electron transfer sequence to the putative cytochrome bo.
I. P Del Arenal Departamento de Bioquímica, Facultad de Medicina, Universidad Nacional Autónoma de México, Apartado postal 70–159, 04510 México, D.F, México J. R. Dávila Escuela de Biología, Universidad Autónoma de Puebla, Puebla, Mexico M. L. Contreras · B. B. Svlateorova · P. Rangel · F. Lledías · J. E. Escamilla (Y) Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Apartado postal 70–242, 04510 México, D.F., México Tel. +525 622-5627/5628; Fax +525 622-5630 e-mail: [email protected]
Key words Bacillus cereus · Haem O · Cytochrome bo · Cytochrome aa3 · cytochrome caa3 · Bacillus sporulation Abbreviations TMPD N, N, N′, N′-Tetramethyl-pphenylenediamine · HOQNO · 2n-Heptyl-4hydroxyquinoline-N-oxide; DCPIP 2,6-Dichlorophenolindophenol
Introduction Bacillus subtilis (Saraste et al. 1991; Van der Oost et al., 1991) and Bacillus cereus (García-Horsman et al. 1991a, b) can synthesize two oxidases that contain haem A: cytochrome aa3 and cytochrome caa3. The expression of these enzymes depends on the carbon source (Saraste et al. 1991; Van der Oost et al. 1991) and on the morphogenetic stage of the culture (García-Horsman et al. 1991a, b). Early studies on respiratory mutants of B. subtilis affected in the expression of a-type cytochromes led to the notion that mutants lacking oxidase aa3 are asporogenic (Taber 1974; Young and Mandelstam 1979; Mueller and Taber 1989). Howe
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