Journal
EMBO JOURNAL
Volume 26, Issue 15, Pages 3662-3672Publisher
NATURE PUBLISHING GROUP
DOI: 10.1038/sj.emboj.7601787
Keywords
anaerobic nitrate regulator (ANR); anaerobic respiration; biofilms; nitric oxide; Pseudomonas aeruginosa
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Funding
- NIAID NIH HHS [AI-53079, R01 AI050812-05, R01 AI050812, R03 AI053079] Funding Source: Medline
- NIGMS NIH HHS [R01 GM024689, R37 GM024689, GM-24689] Funding Source: Medline
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Protection from NO gas, a toxic byproduct of anaerobic respiration in Pseudomonas aeruginosa, is mediated by nitric oxide (NO) reductase (NOR), the norCB gene product. Nevertheless, a norCB mutant that accumulated similar to 13.6 mu M NO paradoxically survived anaerobic growth. Transcription of genes encoding nitrate and nitrite reductases, the enzymes responsible for NO production, was reduced > 50- and 2.5-fold in the norCB mutant. This was due, in part, to a predicted compromise of the [4Fe-4S](2+) cluster in the anaerobic regulator ANR by physiological NO levels, resulting in an inability to bind to its cognate promoter DNA sequences. Remarkably, two O-2-dependent dioxygenases, (h) under baro (m) under baro (g) under bar entisate-1,2-dioxygenase (HmgA) and 4- (h) under bar ydroxyphenyl (p) under bar yruvate (d) under bar ioxygenase (Hpd), were derepressed in the norCB mutant. Electron paramagnetic resonance studies showed that HmgA and Hpd bound NO avidly, and helped protect the norCB mutant in anaerobic biofilms. These data suggest that protection of a P. aeruginosa norCB mutant against anaerobic NO toxicity occurs by both control of NO supply and reassignment of metabolic enzymes to the task of NO sequestration.
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