Biodegradable mulch film is considered a promising alternative to traditional plastic mulch film. However, biodegradable mulch film-derived microplastics (BMPs) in the environment have been reported as carriers for herbicides. Particularly in agricultural settings, limited attention has been given to the abiotic and biological aging processes of BMPs, as well as the herbicides adsorption mechanisms and associated health risks of BMPs. This study investigated the adsorption behaviors and mechanisms of mesotrione on both virgin and aged polylactic acid (PLA)/poly (butylene adipate-co-terephthalate) (PBAT) BMPs, and further evaluated their bioaccessibilities in gastrointestinal fluids. A variety of physical and chemical methods, including scanning electron microscopy (SEM), fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS), revealed increased roughness, generation of oxygen-containing functional groups, and higher O/C ratios of PLA/ PBAT BMPs after ultraviolet (UV) and microbial aging processes. Both UV aging and microbial aging significantly enhanced the adsorption levels of mesotrione on PLA and PBAT BMPs by approximately two-fold, driven by pore filling, hydrogen bonding, and it-it conjugation. The adsorption capacity of mesotrione on BMPs decreased with the pH from 3.0 to 11.0, which was involved by electrostatic interactions. In addition, salt ionic strength (Na+, Ca2+, Mg2+, Fe3+) generally inhibited the adsorption due to ions competition for adsorption sites. Notably, mesotrione exhibited high bioaccessibility when adsorbed onto BMPs, with aged BMPs exhibiting greater desorption quantities in gastrointestinal fluids compared to virgin BMPs. These findings provide effective insights into the potential health threats posed by BMPs carrying herbicides in the environment and offer applicable guidance for managing and remediating composite pollution involving BMPs and adsorbed contaminants.

A Gram-stain-positive, facultatively anaerobic, rod-shaped bacterium, designated JX-17(T), was isolated from a soil sample collected in Jiangxi Province, PR China. Growth was observed at 15-48(degrees)C (optimum 37 C-degrees), at pH 5.0-9.0 (optimum pH 7.0) and with 0-6.0% (w/v) NaCl (optimum 1.0%). Strain JX-17(T) could degrade approximately 50% of 50 mg/L mesotrione within 2 days of incubation, but could not use mesotrione as sole carbon source for growth. Strain JX-17(T) showed less than 95.3% 16S rRNA gene sequence similarity with type strains of the genus Paenibacillus. In the phylogenetic tree based on 16S rRNA gene and genome sequences, strain JX-17(T) formed a distinct lineage within the genus Paenibacillus. The ANI values between JX-17(T) and the most closely related type strains P. lentus CMG1240(T) and P. farraposensis UY79(T) were 70.1% and 71.4%, respectively, and the dDDH values between them were 19.0% and 23.3%, respectively. The major cellular fatty acids were anteiso-C-15:0, iso-C-16:0, anteiso-C-17:0 and C-16:0, the predominant respiratory quinone was MK-7, the major polar lipids were diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol, an unidentified glycolipid, an aminophospholipid and a phosphatidylinositol. The diagnostic diamino acid of the peptidoglycan was meso-diaminopimelic acid, and the DNA G + C content was 50.1 mol%. Based on the phylogenetic, phenotypic and chemotaxonomic characteristics, strain JX-17(T) represents a novel species within the genus Paenibacillus, for which the name Paenibacillus lacisoli sp. nov is proposed, with strain JX-17(T) (= GDMCC 1.3962(T) = KCTC 43568(T)) as the type strain.

Mesotrione is an emerging environmental contaminant with potential hazards to agricultural environment and nontarget organisms. Microbes are major drivers of mesotrione biodegradation. However, understanding of the degradation characteristics, mechanisms and potential applications of the reported bacteria that can be utilized to eliminate mesotrione is very limited. Here, a novel mesotrione-degrading Klebsiella pasteurii CM -1 with excellent environmental adaptability was isolated, which could completely degrade 100 mg/L mesotrione within 20 h under the optimal condition. Metabolic pathway analysis showed that CM -1 degraded mesotrione to 2-(2hydroxyamino-4-(methylsulfonyl)benzoyl)cyclohexane-1,3-dione, 1,3-dihydro-3-hydroxy-6-(methylsulfonyl) benzo[c]isoxazol-3-yl)cyclohexane-1,3-dione and 2-amino-4-methylsulfonylbenzoic acid. The predicted toxicities of these metabolites were lower than that of mesotrione. Combining genomic analysis and RT-qPCR, nitroreductase-encoding genes nfsA and nfsB were identified as key players driving mesotrione biodegradation. Molecular docking results suggested that residues His215 and Arg218 of NfsA and Lys14, Thr41 and Phe124 of NfsB might be the key sites for their binding to mesotrione. Purified enzyme in vitro assays indicated that NfsA and NfsB could degrade mesotrione under various conditions, and converted it to the same products as CM -1. Some metal cations could significantly enhance the activity of NfsA and NfsB. The Km values of NfsA and NfsB for mesotrione were 0.453 and 1.075 mmol/L. Furthermore, CM -1 could rapidly remove 97.21/96.50% of mesotrione (50 mg/kg) in nonsterilized/sterilized soil within 4 d. This study provided an efficient bioresource with remediation potential for mesotrione residual pollution and new insights into the mechanism of bacterialmediated mesotrione degradation.