Phthalates Promote Dissemination of Antibiotic Resistance Genes: An Overlooked Environmental Risk

Abstract

Plastics–microorganism interactions have aroused growing environmental and ecological concerns. However, previous studies concentrated mainly on the direct interactions and paid little attention to the ecotoxicology effects of phthalates (PAEs), a common plastic additive that is continuously released and accumulates in the environment. Here, we provide insights into the impacts of PAEs on the dissemination of antibiotic resistance genes (ARGs) among environmental microorganisms. Dimethyl phthalate (DMP, a model PAE) at environmentally relevant concentrations (2–50 μg/L) significantly boosted the plasmid-mediated conjugation transfer of ARGs among intrageneric, intergeneric, and wastewater microbiota by up to 3.82, 4.96, and 4.77 times, respectively. The experimental and molecular dynamics simulation results unveil a strong interaction between the DMP molecules and phosphatidylcholine bilayer of the cell membrane, which lowers the membrane lipid fluidity and increases the membrane permeability to favor transfer of ARGs. In addition, the increased reactive oxygen species generation and conjugation-associated gene overexpression under DMP stress also contribute to the increased gene transfer. This study provides fundamental knowledge of the PAE–bacteria interactions to broaden our understanding of the environmental and ecological risks of plastics, especially in niches with colonized microbes, and to guide the control of ARG environmental spreading.

Determining the Contribution of Micro/Nanoplastics to Antimicrobial Resistance: Challenges and Perspectives

“…Microplastics with different biodegradability show varying adsorption capacities for different environmental contaminants, which can possibly influence microbial growth and compositions or induce ROS overgeneration by biotoxicity, resulting in changes in ARG abundance and dissemination . For example, the biodegradable PBAT showed greater adsorption capacities to phenanthrene than two types of nonbiodegradable plastics (PE and PS) .…”

“…It has been proposed that nonbiodegradable plastic PE mulch had the highest leaching potential of PAEs (6.88 μg/g), followed by PE bags (4.24 μg/g), while it was lower for biodegradable PLA mulch (1.10 μg/g) and PBAT/PLA bags (0.89 μg/g)) . PAEs could increase the plasmid-mediated conjugation transfer of ARGs by lowering the membrane lipid fluidity, increasing the membrane permeability, generating excess ROS, and expressing the conjugation-associated gene at environmentally relevant concentrations (2–50 μg/L) …”

Underestimated Risks of Microplastics on the Environmental Spread of Antibiotic Resistance Genes

“…Bacterial exposed to toxic contaminants may form more holes in the cell membrane to allow not only promote adhesive pilis production for enhancing cell contact but also directly accelerate plasmid-mediated ARGs transmission . The increase of intracellular ROS concentration will change cell membrane structure, and the increased membrane permeability makes it easier for bacteria to take up extracellular DNA and promote the entry and exit of plasmids from the cell, thus promoting the transformation and conjugation transfer of ARGs …”

“…Another relatively overlooked impact is the MP-embodied chemical additives, which may be continuously released into the environment. 16 Because most chemical additives (e.g., plasticizers, flame retardants, colorants, antioxidants, stabilizers, and antistatic agents) are not chemically linked to the plastic polymers, they are easily leached from plastics during material degradation and weathering. The common plastic additives such as bisphenol A, phthalates and polybrominated diphenyl ethers could all be important causes of MP toxicity.…”

“…7 The increase of intracellular ROS concentration will change cell membrane structure, and the increased membrane permeability makes it easier for bacteria to take up extracellular DNA and promote the entry and exit of plasmids from the cell, thus promoting the transformation and conjugation transfer of ARGs. 16 Bacterial quorum sensing (QS) may also be an important pathway of MP-regulated ARGs spreading (Figure 1). QS supports cell-to-cell communication through signaling molecules, allowing them to respond quickly to population density changes.…”