Effects of parabens exposure on drinking water bacteria

Parabens are considered emerging contaminants that are frequently detected in water sources. Besides being detected in drinking water (DW) at residual concentrations, their effects on DW microbial quality and safety have been disregarded so far. This work assesses for the first time the impact of methylparaben (MP), propylparaben (PP), and butylparaben (BP) on selected bacteria isolated from DW: Acinetobacter calcoaceticus and Stenotrophomonas maltophilia. Although the minimum inhibitory concentrations (MICs) values obtained were found to be much higher (200 - 400 mg/L) than concentrations of parabens found in the environment, parabens induce bacterial membrane modifications at environmental concentrations (15 µg/L). Overall, parabens caused an increase in the total surface hydrophilicity of both bacteria, being this effect more pronounced for MP and BP on S. maltophilia. Dual-species biofilms grown on polypropylene (PPL) and high-density polyethylene (HDPE) and exposed to MP (15 µg/L) were found to be more metabolically active (198% and 98%, respectively) than non-exposed biofilms. Even though, MP (15 µg/L) was able to reduce the cell growth rate of A. calcoaceticus from dual-species biofilms. The overall results show that parabens induce modifications in bacterial community characteristics and behaviour, which may compromise the safety of DW.