2.2. Bacterial Strains and Culture Conditions

The P. aeruginosa PA14 wild-type (WT) strain and derived mutants (ΔlasR/ΔrhlR and ΔpscC) used in this study are listed in Table S2. In the case of C. violaceum, the ATCC^® 31532™ (The American Type Culture Collection, Manassas, VA, USA) WT and the mutant ΔcviI (CV026, CDBB1423) strains were obtained from Colección Nacional de Cepas Microbianas y Cultivos Celulares, CINVESTAV (CINVESTAV-IPN, CDMX, Mexico) (Table S2).

The ΔescU mutant strain was constructed by allelic exchange using the recombinant suicide plasmid pRE112. Briefly, the pRE112 plasmid containing 770 bp of DNA upstream and 896 bp of DNA downstream of the escU gene was conjugated from the E. coli SM10 λ pir (ATCC^® 87450TM, The American Type Culture Collection, Manassas, VA, USA) donor strain into the C. violaceum WT strain. Colonies from the first homologous recombination event were selected for chloramphenicol resistance (15 μg/mL) and for violacein production (purple colonies). The second event of recombination was selected on LB plates containing 5% sucrose. Elimination of the escU gene from the chromosome was corroborated by PCR.