Pseudomonas aeruginosa AlgB, which modulates the expression of alginate, is a member of the NtrC subclass of prokaryotic regulators.

The Pseudomonas aeruginosa exopolysaccharide alginate is an important virulence factor in chronic pulmonary infections of cystic fibrosis patients. We determined the nucleotide sequence of the gene, algB, which regulates the level of exopolysaccharide produced by mucoid P. aeruginosa. The predicted amino acid sequence of AlgB revealed a high degree of similarity to the regulatory proteins in the NtrC subclass of 'two-component regulatory systems'. AlgB expression in Escherichia coli minicells showed a molecular weight of approximately 50,000 Da, comparable to that of the inferred amino acid sequence (49,318 Da). We show that algB is transcriptionally active in mucoid strains of P. aeruginosa and regulates the expression of the alginate biosynthetic gene, algD, thereby resulting in increased expression of alginate in mucoid P. aeruginosa.