Parabens alter the surface characteristics and antibiotic susceptibility of drinking water bacteria

Parabens are markedly present in products of daily use, considered emerging environmental contaminants that can harm human health and aquatic life, due to their release into aquatic sources. The impact of the exposure of microbial communities to parabens remains unclear. This study investigates aspects of the mode of action of methylparaben (MP), propylparaben (PP), butylparaben (BP), and MIX at environmental (15 μg/L) and in-use (15000 μg/L) concentrations, against two bacterial strains of Acinetobacter calcoaceticus and Stenotrophomonas maltophilia previously isolated from drinking water (DW). BP showed the strongest antimicrobial activity, while MP exhibited the weakest. The mechanism of action of parabens at the selected concentrations was found to be related to perturbations on physicochemical bacterial cell surface properties and charge, by causing an increase of bacterial cell envelope hydrophilicity and zeta potential values. In addition, parabens may activate osmotic regulation mechanisms as observed by the increase in vacuole area for MP-exposed A. calcoaceticus. The bacterial metabolic activity as well as bacterial size was also affected by parabens exposure. MP exposure further enhanced the biofilm formation ability and increased bacterial tolerance to antibiotics. The results raise environmental implications, particularly concerning water quality and public health, as parabens exposure can potentiate the virulence of DW bacteria, increasing the risk of human exposure to harmful microorganisms.