We found a match
Your institution may have rights to this item. Sign in to continue.
- Title
Physiological levels of nitrate support anoxic growth by denitrification of Pseudomonas aeruginosa at growth rates reported in cystic fibrosis lungs and sputum.
- Authors
Line, Laura; Alhede, Morten; Kolpen, Mette; Kühl, Michael; Ciofu, Oana; Bjarnsholt, Thomas; Moser, Claus; Masanori Toyofuku; Nobuhiko Nomura; Høiby, Niels; Jensen, Peter Ø.
- Abstract
Chronic Pseudomonas aeruginosa lung infection is the most severe complication in patients with cystic fibrosis (CF). The infection is characterized by the formation of biofilm surrounded by numerous polymorphonuclear leukocytes (PMNs) and strong O2 depletion in the endobronchial mucus. We have reported that O2 is mainly consumed by the activated PMNs, while O2 consumption by aerobic respiration is diminutive and nitrous oxide (N2O) is produced in infected CF sputum. This suggests that the reported growth rates of P. aeruginosa in lungs and sputum may result from anaerobic respiration using denitrification. The growth rate of P. aeruginosa achieved by denitrification at physiological levels (∼400μM) of nitrate (NO-3 ) is however, not known. Therefore, we have measured growth rates of anoxic cultures of PAO1 and clinical isolates (n = 12) in LB media supplemented with NO-3 and found a significant increase of growth when supplementing PAO1 and clinical isolates with ⩾150μMNO-3 and 100μMNO-3 , respectively. An essential contribution to growth by denitrification was demonstrated by the inability to establish a significantly increased growth rate by a denitrification deficient ΔnirS-N mutant at <1mM of NO-3 . Activation of denitrification could be achieved by supplementation with as little as 62.5μM of NO-3 according to the significant production of N2O by the nitrous oxide reductase deficient ΔnosZ mutant. Studies of the promoter activity, gene transcripts, and enzyme activity of the four N-oxide reductases in PAO1 (Nar, Nir, Nor, Nos) further verified the engagement of denitrification, showing a transient increase in activation and expression and rapid consumption of NO-3 followed by a transient increase of NO-2 . Growth rates obtained by denitrification in this study were comparable to our reported growth rates in the majority of P. aeruginosa cells in CF lungs and sputum. Thus, we have demonstrated that denitrification is required for P. aeruginosa growth in infected endobronchial CF mucus.
- Subjects
PSEUDOMONAS aeruginosa; CYSTIC fibrosis; LUNG infections; NITRATES; DENITRIFICATION; SPUTUM; DISEASE complications; NEUTROPHILS
- Publication
Frontiers in Microbiology, 2014, Vol 5, p1
- ISSN
1664-302X
- Publication type
Article
- DOI
10.3389/fmicb.2014.00554