The O2-independent pathway of ubiquinone biosynthesis is essential for denitrification in Pseudomonas aeruginosa — Ubiquinone is essential for denitrification in P. aeruginosa — The O2-independent pathway of ubiquinone biosynthesis is essential for denitrification in Pseudomonas aeruginosa — Ubiquinone is essential for denitrification in P. aeruginosa