Transporters and Efflux Pumps Are the Main Mechanisms Involved in Adaptation and Tolerance to Didecyldimethylammonium Chloride.

cleanroom strains are often exposed to sub-inhibitory concentrations of disinfectants, including didecyldimethylammonium chloride (DDAC). Consequently, they can adapt or even become tolerant to them. RNA-sequencing was used to investigate adaptation and tolerance mechanisms of cleanroom strains (SE11, SE18), with SE11Ad adapted and SE18To tolerant to DDAC. Adaptation to DDAC was identified with up-regulation of genes mainly involved in transport (thioredoxin reductase [], the arsenic efflux pump [gene ID, SE0334], sugar phosphate antiporter []), while down-regulation was seen for the Agr system (, , , , SE1543), for enhanced biofilm formation. Tolerance to DDAC revealed the up-regulation of genes associated with transporters (L-cysteine transport []; uracil permease [SE0875]; multidrug transporter []; arsenic efflux pump []); the down-regulation of genes involved in amino-acid biosynthesis (lysine []; histidine []; methionine []), and an enzyme involved in peptidoglycan, and therefore cell wall modifications (alanine racemase [SE1079]). We show for the first time the differentially expressed genes in DDAC-adapted and DDAC-tolerant strains, which highlight the complexity of the responses through the involvement of different mechanisms.