Colonization of phthalate-degrading endophytic bacterial consortium altered bacterial community and enzyme activity in plants.

Phthalates (PAEs) are widely distributed hazardous organic compounds that pose threats to ecosystems and human health. Endophytic bacteria can effectively eliminate PAEs contamination risk. However, limited information is available regarding the impact of endophytic bacterial colonization on bacterial communities within plants. In this study, the endophytic bacterial consortium EN was colonized in lettuce by seed soaking, root irrigation, leaf spraying, and combined spraying-irrigation, resulting in a marked improvement in plant growth. The findings revealed that consortium EN colonization through combined spraying-irrigation exhibited superior degradation capability with 40.54% PAEs removal from soil. Meanwhile, the residual PAEs in lettuce decreased by 94.05% compared with the uninoculated treatment. High-throughput sequencing analysis indicated that colonization of consortium EN altered the bacterial community in lettuce. Specifically, the relative abundance of the dominant genus Pseudomonas was significantly higher than that in the uninoculated control (P < 0.01). Additionally, colonization enhanced the activities of peroxidase and catalase in lettuce, thereby improving plant resistance. This work offers a theoretical foundation for comprehending the mechanism underlying the bioremediation of PAEs contamination by endophytic bacteria in soil-plant system.

Biodegradation of PAEs in contaminated soil by immobilized bacterial agent and the response of indigenous bacterial community.

Phthalic acid esters (PAEs) are common hazardous organic contaminants in agricultural soil. Microbial remediation is an effective and eco-friendly method for eliminating PAEs. Nevertheless, the operational mode and potential application of immobilized microorganisms in PAEs-contaminated soil are poorly understood. In this study, we prepared an immobilized bacterial agent (IBA) using a cedar biochar carrier to investigate the removal efficiency of PAEs by IBA in the soil. We found that IBA degraded 88.35% of six optimal-control PAEs, with 99.62% biodegradation of low-molecular-weight PAEs (DMP, DEP, and DBP). The findings demonstrated that the IBA achieved high efficiency and a broad-spectrum in degrading PAEs. High-throughput sequencing revealed that IBA application altered the composition of the soil bacterial community, leading to an increase in the relative abundance of PAEs-degrading bacteria (Rhodococcus). Furthermore, co-occurrence network analysis indicated that IBA promoted microbial interactions within the soil community. This study introduces an efficient method for the sustainable remediation of PAEs-contaminated soil.

Molecular clusters played an important role in the adsorption of polycyclic aromatic hydrocarbons (PAHs) on carbonaceous materials.

Polycyclic aromatic hydrocarbons (PAHs) are one of the most frequently detected hydrophobic organic contaminants (HOCs) in the environment. They may form clusters because of the strong hydrophobic and π-π electron-donor-acceptor (EDA) interactions among PAHs molecules. However, previous experimental studies and theoretical simulations generally ignored the impact of molecular clusters on the adsorption, which may result in the misunderstanding of the environmental fate and risk. In this work, naphthalene (NAP), phenanthrene (PHE), and pyrene (PYR) were selected to investigate intermolecular interaction as well as the consequent impact on their adsorption on graphene. The density field of C atoms in equilibrium configurations of self-interacted PAHs suggested that the formation of PAHs molecular clusters was a spontaneous process, and was favored in solvents with stronger polarity and for PAHs with more benzene rings. It should be noted that the molecular dynamics simulations with the initial state of molecular clusters matched better with the published experimental results compared with those of individual PAHs. The formed compact PAHs clusters in polar solvents increased the apparent PAHs adsorption, because of their higher hydrophobic and π-π EDA interactions. This study emphasized that the self-interaction of PAHs should be carefully considered in both experimental and theoretical simulation studies.

Competitive adsorption of methanol co-solvent and dioctyl phthalate on functionalized graphene sheet: Integrated investigation by molecular dynamics simulations and quantum chemical calculations.

HYPOTHESIS: Organic co-solvents, which are universally employed in adsorption studies of hydrophobic organic chemicals (HOCs), can inhibit HOC adsorption by competing for active sites on the adsorbent. The adsorbent structure can influence co-solvent interference of HOC adsorption; however, this effect remains unclear, leading to an incomplete understanding of the adsorption mechanism. EXPERIMENTS: In this study, dioctyl phthalate (DOP) was used to investigate competitive adsorption on functionalized graphene sheet in a water-methanol co-solvent system through molecular dynamics simulations and quantum chemical calculations. FINDINGS: The simulations showed that the functional groups in the graphene defects had a strong adsorption affinity for methanol. The adsorbed methanol occupied a large number of active sites at the graphene center, thereby weakening DOP adsorption. However, the methanol adsorbed at the graphene edges could not compete with DOP for the active sites. -COOH had the strongest binding affinity for methanol among the functional groups and thus predominantly controlled the interaction between graphene and methanol. This study makes an innovative contribution toward understanding the competitive adsorption of methanol and DOP on functionalized graphene sheet, especially in visualizing the competition for active sites, and provides theoretical guidance for the removal of HOCs and practical application of graphene.