Conversion of Pseudomonas aeruginosa to mucoidy in cystic fibrosis: environmental stress and regulation of bacterial virulence by alternative sigma factors.

TLDR: The conversion of Pseudomonas aeruginosa into the mucoid, exopolysaccharide alginate-overproducing form is considered to be a major pathogenic determinant expressed by this organism during chronic respiratory infections in cystic fibrosis.

Abstract: The conversion of Pseudomonas aeruginosa into the mucoid, exopolysaccharide alginate-overproducing form is considered to be a major pathogenic determinant expressed by this organism during chronic respiratory infections in cystic fibrosis (CF) (5, 28, 32). Despite the fact that CF has a relatively recent history as a medically recognized syndrome (since 1938), the problem of conversion to mucoidy in P. aeruginosa has become an instant classic of microbial pathogenesis (for recent reviews, see references 28, 54, and 61). Most P. aeruginosa strains have the genetic capacity to synthesize alginate, but mucoid mutants that overproduce this exopolysaccharide are rarely noticed among environmental isolates. In contrast, P. aeruginosa strains from CF are frequently mucoid (28, 32). Several mutations causing conversion to mucoidy (see Fig. 1) and genes that participate in these processes have been recently defined (see Table 1); the mutations are superimposed on a system consisting of a putative alternative sigma factor, which most likely plays a more general role in bacterial stress response, and its accessory negative regulators (23, 30, 51-53, 61).