f The Klebsiella pneumoniae cytochrome bd’ terminal oxidase complex and its role in microaerobic nitrogen fixation
- Authors: Navtej S. Juty‡, Farhad Moshiri†, Mike Merrick, Christopher Anthony, Susan Hill1
- 1 Author for correspondence: Susan Hill. Tel: +44 1603 456900 ext. 2749. Fax: +44 1603 454970.
- Microbiology, August 1997 143: 2673-2683, doi: 10.1099/00221287-143-8-2673
- Subject: Physiology And Growth
- Published Online:
Summary: Cytochrome bd’ has been implicated in having an important role in microaerobic nitrogen fixation in the enteric bacterium Klebsiella pneumoniae, where it is expressed under all conditions that permit diazotrophy. In this paper the sequence of the genes encoding this terminal oxidase (cydAB) of Klebsiella pneumoniae and the characterization of a cyd mutant are reported. The deduced amino acid sequences support the proposal that His 19, His 186 and Met 393 provide three of the four axial ligands to the Fe of the three haems in the oxidase complex. The nitrogen-fixing ability of the mutant was severely impaired in the presence of low concentrations of oxygen compared with the wild-type bacterium. Only the wild-type organism was capable of microaerobic nitrogenase activity supported by fermentation products. It is proposed that formate dehydrogenase-O may be involved in supplying electrons to a respiratory chain terminated by the bd-type oxidase, which would remove inhibitory oxygen and supply ATP for nitrogenase activity.
Present address: Mail Zone GG4G, gen, A Unit of Monsanto, 700 Chesterfield Parkway, St Louis 63198 USA.
Present address: City of National Medical Center, Division of Pediatrics, 1500 East Duarte Road CA 91010-0269, USA.
© Society for General Microbiology 1997 | Published by the Microbiology Society
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