In:
Journal of Bacteriology, American Society for Microbiology, Vol. 183, No. 24 ( 2001-12-15), p. 7076-7086
Abstract:
The cydAB genes from Mycobacterium smegmatis have been cloned and characterized. The cydA and cydB genes encode the two subunits of a cytochrome bd oxidase belonging to the widely distributed family of quinol oxidases found in prokaryotes. The cydD and cydC genes located immediately downstream of cydB encode a putative ATP-binding cassette-type transporter. At room temperature, reduced minus oxidized difference spectra of membranes purified from wild-type M. smegmatis displayed spectral features that are characteristic of the γ-proteobacterial type cytochrome bd oxidase. Inactivation of cydA or cydB by insertion of a kanamycin resistance marker resulted in loss of d- heme absorbance at 631 nm. The d -heme could be restored by transformation of the M. smegmatis cyd mutants with a replicating plasmid carrying the highly homologous cydABDC gene cluster from Mycobacterium tuberculosis . Inactivation of cydA had no effect on the ability of M. smegmatis to exit from stationary phase at 37 or 42°C. The growth rate of the cydA mutant was tested under oxystatic conditions. Although no discernible growth defect was observed under moderately aerobic conditions (9.2 to 37.5 × 10 2 Pa of pO 2 or 5 to 21% air saturation), the mutant displayed a significant growth disadvantage when cocultured with the wild type under extreme microaerophilia (0.8 to 1.7 × 10 2 Pa of pO 2 or 0.5 to 1% air saturation). These observations were in accordance with the two- to threefold increase in cydAB gene expression observed upon reduction of the pO 2 of the growth medium from 21 to 0.5% air saturation and with the concomitant increase in d -heme absorbance in spectra of membranes isolated from wild-type M. smegmatis cultured at 1% air saturation. Finally, the cydA mutant displayed a competitive growth disadvantage in the presence of the terminal oxidase inhibitor, cyanide, when cocultured with wild type at 21% air saturation in an oxystat. In conjunction with these findings, our results suggest that cytochrome bd is an important terminal oxidase in M. smegmatis.
Type of Medium:
Online Resource
ISSN:
0021-9193
,
1098-5530
DOI:
10.1128/JB.183.24.7076-7086.2001
Language:
English
Publisher:
American Society for Microbiology
Publication Date:
2001
detail.hit.zdb_id:
1481988-0
SSG:
12
