Growth and alginate production of P. aeruginosa under aerobic versus anaerobic conditions. (a) Growth of P. aeruginosa in NL or CF ASL under aerobic or anaerobic conditions. Two strains, PAO1 (black bars) and ATCC 700829 (gray bars), were inoculated (∼100–200 bacteria, dashed line) in 30 μl NL or CF ASL and number of bacteria quantitated 72 hours later. The results presented are from a single representative experiment of three performed. The differences in the CFU/ml in the three experiments were less than 0.3 log 10. (b) Immunofluorescence detection of alginate production by PAO1 after aerobic (8 hours; left) or anaerobic (12 hours; right) conditions (magnification, ×1,000; bars, 10 μm). (c) Alginate production of PAO1 by the carbazole assay after growth under anaerobic (black bar) or aerobic (white bar) conditions for 4 days without added nitrate. *P < 0.05. (d) Alginate production per microgram bacterial protein mass of PAO1 as a function of the added NO₃^– to PIA under aerobic (white bars) and anaerobic (black bars) conditions. (e) pO₂ (filled squares) in an aerobically growing suspension of P. aeruginosa (open triangles) as a function of time (hours). (f) Mathematical analysis of depths from air-mucus interface at which pO₂ becomes zero for simulated mucus masses/plaques containing different concentrations of P. aeruginosa bacteria (colony-forming units per milliliter).