Estrogen mimics induce genes encoding chemical efflux proteins in gram-negative bacteria

Area of Science:

• Environmental microbiology
• Molecular biology
• Toxicology

Background:

• Gram-negative bacteria, including Escherichia coli and Pseudomonas aeruginosa, inhabit wastewater and biosolids.
• Resistance-nodulation-cell division (RND) superfamily efflux pumps are crucial for bacterial detoxification against antibiotics and toxins.
• Estrogenic endocrine disruptors are prevalent wastewater pollutants with potential impacts on microbial systems.

Purpose of the Study:

• To investigate the effect of common wastewater estrogenic endocrine disruptors on RND efflux pump gene expression in E. coli and P. aeruginosa.
• To determine if RND gene expression can serve as a biomarker for the interaction between estrogen mimics and bacterial detoxification systems.

Main Methods:

• Exposure of E. coli and P. aeruginosa to environmental concentrations of 17α-ethynylestradiol, nonylphenol, and bisphenol-A.
• Quantitative real-time PCR (q-PCR) to analyze the expression levels of specific RND efflux pump genes.

Main Results:

• In E. coli, exposure to the three chemicals significantly over-expressed the acrB and yhiV genes, confirming their role in hormone transport.
• In P. aeruginosa, differential expression of 12 RND efflux pumps was observed: mexD and mexF were upregulated by all three chemicals, while mexK, mexW, and triC were upregulated by nonylphenol and bisphenol-A.
• Gene expression analysis via q-PCR demonstrated a correlation between estrogen mimic exposure and RND gene induction.

Conclusions:

• Estrogenic endocrine disruptors induce the expression of RND efflux pump genes in bacteria.
• Bacterial RND efflux pumps play a role in the detoxification and expulsion of estrogenic compounds from the cell.
• q-PCR analysis of RND gene expression is a viable method for predicting bacterial interactions with estrogen mimics.