Effects and mechanisms of phthalates on the transformation of antibiotic resistance genes into <italic>Escherichia coli</italic>

Abstract

<p indent="0mm">The horizontal transfer of antibiotic resistance genes (ARGs) is the fundamental cause of the spread of antibiotic resistance, which seriously threatens ecological security and public health. Transformation is an important way of ARGs horizontal transfer. Phthalates (PAEs) and ARGs can form compound pollution. However, the effects of PAEs on the transformation process of ARGs remain poorly understood. Thus, transformation experiments were carried out to explore the influence and mechanism of typical PAEs on the transformation of ARGs into <italic>Escherichia coli </italic>(<italic>E</italic>.<italic> coli</italic>). It was found that dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP), di(2-ethylhexyl) phthalate (DEHP), and benzyl butyl phthalate (BBP) at lower than its minimum inhibitory concentration (MIC) respectively reduced the transformation efficiency of ARGs by 27.55%, 32.71%, 46.40%, 38.36%, and 59.87%, and the transformation frequency of ARGs also decreased obviously with the increase of PAEs concentrations. The results indicated that PAEs inhibited the transformation of ARGs into <italic>E</italic>.<italic> coli</italic>. PAEs induced plasmids carrying ARGs to form larger aggregates, reduced cell membrane permeability of recipient cells, caused an increase of oxidative stress in recipient cells, down-regulated the expression of genes involved in adenosine triphosphate (ATP) conversion, finally resulted in the inhibitory effect of ARGs transformation. This work revealed the mechanism of PAEs inhibiting the transformation of ARGs at cellular and molecular levels. The results will have scientific significance for understanding the molecular ecological effects of PAEs pollution in the environment.