MucE-mediated mucoid conversion in nonmucoid clinical isolates is dependent on MucA length and algU genotype. The length of MucA is shown with two functional domains as depicted with RseA_N and RseA_C, which represent the N-terminal domain of MucA predicted to interact with AlgU in the cytoplasm and C-terminal domain of MucA located in the periplasm, respectively. The domain prediction is based on the NCBI Conserved Domain Database (CDD). The blue vertical line represents the truncated MucA due to the mutation from each CF strain relative to the full length of wild type MucA. The type of AlgU is indicated for each CF strain (WT or mutant with the indicated change of amino acid due to missense mutation). Those strains that become mucoid upon mucE induction are shown in red, while those that remain nonmucoid are shown in black. The red arrow indicates the cutting site of MucA by AlgW. pHERD20T-mucE was conjugated into these non-mucoid CF isolates, and then incubated on PIA plates containing carbenicillin and 0.1% L-arabinose at 37°C for 24 hours. Mucoid or non-mucoid phenotype was scored based on visual inspection and the amount of alginate production. The quantity of alginate was measured and shown in Table S2.