Evidence for two promoters internal to the alginate biosynthesis operon in Pseudomonas aeruginosa

While much is known about the transcriptional regulation of the 12 gene alginate biosynthesis operon from the algD promoter in Pseudomonas aeruginosa, there has been little investigation into the possibility of other transcription starts within this operon, especially those genes dealing with the epimerization and acetylation of the alginate polymer. In this study, we utilized quantitative reverse transcription polymerase chain reaction, a β-galactosidase reporter assay and sequence scanning to identify two putative promoters within the alginate biosynthesis operon upstream of the alginate epimerase gene algG and the alginate acetylation gene algI. These data support the possibility of differential regulation within the operon to alter polymer structure under varying environmental conditions.