Dysregulation of denitrification in clinical isolates
P. aeruginosa adapts to the CF lung by mutation. The most common
mutation (mucA22) inactivates the anti-sigma factor MucA
which results in overproduction of the exopolysaccharide alginate
and the conversion to a mucoid phenotype (Govan and Deretic,
1996). Regulation and expression ratios of denitrification genes
seem to be altered in mucoid strains. Yoon et al. (2006) discovered
that enzyme activities of the nitrite- and the nitric oxide reductases
are inherently reduced in mucoid isolates. When these strains are
exposed to 15 mM nitrite at pH 6.5, which resembles the pH in
CF airway surface liquid, they die, presumably via NO poisoning.
Therefore, this finding could open a new way to eradicate mucoid
multiresistant P. aeruginosa isolates (Yoon et al., 2006). Another