Aerobic degradation of bisphenol A by Pseudomonas sp. LM-1: characteristic and pathway.

Bisphenol A (BPA) has been widely used in the manufacture of polymeric materials. BPA is regarded as an endocrine disrupting chemical, posing a great threat to the public health. In this study, a bacterial strain LM-1, capable of utilizing BPA as the sole carbon and energy source under aerobic conditions, was originally isolated from an activated sludge sample. The isolate was identified as Pseudomonas sp. based on 16S rRNA gene sequence analysis. Strain LM-1 was able to completely degrade 25-100 mg/L BPA within 14-24 h, and it also exhibited high capacity for BPA degradation at a range of pH (6.0-8.0). (NH4)2SO4 and NH4NO3 were the suitable nitrogen sources for its growth and BPA biodegradation, and the BPA degradation could be accelerated when exogenous carbon sources were introduced as the co-substrates. Metal ions such as Zn2+, Cu2+, and Ni2+ could considerably suppress the growth of strain LM-1 and BPA degradation. According to the analysis of liquid chromatography coupled to Q-Exactive high resolution mass spectrometry, hydroquinone, p-hydroxybenzaldehyde, and p-hydroxybenzoate were the predominate metabolites in the BPA biodegradation and the degradation pathways were proposed. This study is important for assessment of the fate of BPA in engineered and natural systems and possibly for designing bioremediation strategies.

Identification of a MarR Subfamily That Regulates Arsenic Resistance Genes.

In this study, comprehensive analyses were performed to determine the function of an atypical MarR homolog in Achromobacter sp. strain As-55. Genomic analyses of Achromobacter sp. As-55 showed that this marR is located adjacent to an arsV gene. ArsV is a flavin-dependent monooxygenase that confers resistance to the antibiotic methylarsenite [MAs(III)], the organoarsenic compound roxarsone(III) [Rox(III)], and the inorganic antimonite [Sb(III)]. Similar marR genes are widely distributed in arsenic-resistant bacteria. Phylogenetic analyses showed that these MarRs are found in operons predicted to be involved in resistance to inorganic and organic arsenic species, so the subfamily was named MarRars. MarRars orthologs have three conserved cysteine residues, which are Cys36, Cys37, and Cys157 in Achromobacter sp. As-55, mutation of which compromises the response to MAs(III)/Sb(III). GFP-fluorescent biosensor assays show that AdMarRars (MarR protein of Achromobacter deleyi As-55) responds to trivalent As(III) and Sb(III) but not to pentavalent As(V) or Sb(V). The results of RT-qPCR assays show that arsV is expressed constitutively in a marR deletion mutant, indicating that marR represses transcription of arsV. Moreover, electrophoretic mobility shift assays (EMSAs) demonstrate that AdMarRars binds to the promoters of both marR and arsV in the absence of ligands and that DNA binding is relieved upon binding of As(III) and Sb(III). Our results demonstrate that AdMarRars is a novel As(III)/Sb(III)-responsive transcriptional repressor that controls expression of arsV, which confers resistance to MAs(III), Rox(III), and Sb(III). AdMarRars and its orthologs form a subfamily of MarR proteins that regulate genes conferring resistance to arsenic-containing antibiotics. IMPORTANCE In this study, a MarR family member, AdMarRars was shown to regulate the arsV gene, which confers resistance to arsenic-containing antibiotics. It is a founding member of a distinct subfamily that we refer to as MarRars, regulating genes conferring resistance to arsenic and antimony antibiotic compounds. AdMarRars was shown to be a repressor containing conserved cysteine residues that are required to bind As(III) and Sb(III), leading to a conformational change and subsequent derepression. Here we show that members of the MarR family are involved in regulating arsenic-containing compounds.

Bifunctional magnetic ZnCdSe/ZnS quantum dots nanocomposite-based lateral flow immunoassay for ultrasensitive detection of streptomycin and dihydrostreptomycin in milk, muscle, liver, kidney, and honey.

In this study, bifunctional magnetic ZnCdSe/ZnS quantum dots nanocomposite (MQNs) were synthesized, and firstly used to develop a lateral flow immunoassay (LFIA) for streptomycin (STR) and dihydrostreptomycin (DHSTR) detection in milk, muscle, liver, kidney, and honey simultaneously. The fluorescence signal of MQNs was 9-fold stronger than that of the original quantum dots. The detection limits of the established MQNs-LFIA for STR and DHSTR in five samples were 0.08-1.78 µg/kg, the quantitation limits were 0.26-5.87 µg/kg, the recoveries were between 85.0% and 120.0%, and the coefficient of variations were between 0.8% and 19.3%, respectively. The sensitivity was up to 42-fold more sensitive than the reported LFIAs. The single blind test results of 25 samples were consistent with that of the confirmation method (R2 ≥ 0.99). Besides, a portable reader was self-developed and used for rapid quantification. Our study demonstrated MQNs as a promising signal-amplifying tag can be used for ultrasensitive detection of chemical contaminants in foods.

Two kinds of lateral flow immunoassays based on multifunctional magnetic prussian blue nanoenzyme and colloidal gold for the detection of 38 ß-agonists in swine urine and pork.

Herein, novel multifunctional magnetic prussian blue nanoenzymes (MPBNs) and colloidal gold (CG) were synthesized and used to develop two kinds of lateral flow immunoassays (LFIAs) for the detection of 38 ß-agonists. Since MPBNs has a unique three-in-one function of colorimetric magnetic catalytic activities, the signal intensity and coupling ratio are 2 and 8-fold higher than that of the CG. The cut-off values of the CG-LFIA and MPBNs-LFIA for swine urine and pork are 5/5 and 0.3/0.5 µg/kg, the limits of detection are 0.19/0.29 and 0.02/0.03 µg/kg, respectively. The sensitivity of MPBNs-LFIA is 10-fold higher than that of CG-LFIA, and up to 200-fold higher than that of the reported LFIAs. The recoveries of the LFIAs are 80.0%-116.7%, with coefficients of variation of 1.4%-14.3%. Our study proved that the MPBNs have more advantages than CG, and can offer a promising signal label for ultrasensitive immunoassay techniques.

Performance and bacterial community profiles of sequencing batch reactors during long-term exposure to polyethylene terephthalate and polyethylene microplastics.

Microplastics (MPs) are ubiquitous in wastewater treatment plants (WWTPs), but much remains to be learned about their roles in WWTPs. Herein, polyethylene terephthalate (PET) and polyethylene (PE) particles were added into sequencing batch reactors (SBRs), and the sole impacts and co-impacts of MPs with other pollutants (phenol and Cu2+) on wastewater treatment processes were evaluated. Results indicated that MPs did not significantly affect SBR performance, either alone or co-occurrence with phenol, but the co-exposure to MPs and Cu2+ severely suppressed COD removal efficiency by 37.02%-64.70%. The functional groups of activated sludge had no changes after receiving MPs, but the MPs-Cu2+ co-exposure could greatly promote the secretion of extracellular polymeric substances. Furthermore, MPs had no negative impacts on diversity, richness and structure of bacterial communities, and PET and PE showed different preferences for enrichment of bacterial populations. Moreover, the MPs-Cu2+ co-exposure obviously reduced the overall abundances of Cu-related genes in SBRs.

A highly sensitive and quantitative time resolved fluorescent microspheres lateral flow immunoassay for streptomycin and dihydrostreptomycin in milk, honey, muscle, liver, and kidney.

Streptomycin (STR) and dihydrostreptomycin (DHSTR) are clinically widely used in the prevention and treatment of animal diseases. Unreasonable use or abuse can easily cause adverse effects on human health. Thus, it is very necessary to establish a rapid detection method for STR and DHSTR in animal-derived foods. In this study, a time-resolved fluorescent microspheres lateral flow immunoassay (TRFM-LFIA) integrated with a portable fluorescence reader was developed for STR and DHSTR detection. The cut-off values of the TRFM-LFIA for STR and DHSTR in milk/honey/muscle/liver/kidney were both 30/15/80/25/60 µg kg-1, respectively, the limits of detection were 1.10/0.28/2.82/1.52/3.02, 0.75/0.23/1.76/1.21/2.35 µg kg-1, respectively, and the limits of quantitation were 3.62/0.93/9.31/5.02/9.96, 2.48/0.76/5.81/3.99/7.76 µg kg-1, respectively. The recoveries ranged from 80.0% to 120.1%, with coefficient of variation from 2.8% to 14.3%, respectively. The parallel experiment of 25 samples showed excellent correlation (R2 > 0.99) between ELISA kit and TRFM-LFIA. The sample pretreatment is very simple, and the results can be achieved in 8 min. This sensitive, simple, rapid and portable analysis strategy can provide universal technical support for the residue detection of veterinary drugs and even small molecular hazard factors.

Ultrasensitive Magnetic Assisted Lateral Flow Immunoassay Based on Chiral Monoclonal Antibody against R-(-)-Salbutamol of Broad-Specificity for 38 ß-Agonists Detection in Swine Urine and Pork.

Screening for ″zero tolerance″ ß-agonists requires broad-specificity and sensitivity methods. Herein, R-(-)-salbutamol (SAL) is chirally separated and designed as a hapten, and a monoclonal antibody (mAb) was first prepared with an IC50 of 0.27 ng/mL, which can recognize 38 ß-agonists simultaneously. The broad-specificity of chiral mAb was explored by molecular simulation technology. Magnetic nanoparticles (MNPs) were then synthesized and applied as a signal tracer to develop a lateral flow immunoassay (LFIA). The limits of detection of MNPs-LFIA for SAL in swine urine and pork were 0.05 and 0.09 µg/kg, which was (2-125)-fold lower than that of the reported LFIAs. The recoveries were between 95.8 and 116.7%, with the coefficient of variation from 2.7 to 15.4%. Parallel analysis of 44 samples by commercial ELISA kits confirmed the reliability. Therefore, our work not only provides a broad-specificity and ultrasensitive method for ß-agonists but also suggests that chirality is the new general theory that guided the rational hapten design.

Latex microsphere immunochromatography for quantitative detection of dexamethasone in milk and pork.

Dexamethasone (DEX) is a synthetic long-acting glucocorticoid, which can increase the risk of hypertension and diabetes if it is abused or used improperly. In this study, lateral flow immunoassays (LFIA) based on black and blue latex microspheres (LMs), integrated with a strip reader, was developed for quantitative detection of DEX in milk and pork. The results could be achieved within 15 min. The visible limits of detection (vLODs) were 0.3 ng/mL and 0.7 µg/kg for milk and pork, respectively. The quantitative limits of detection (qLODs) were 0.047 ng/mL and 0.087 µg/kg, respectively. The recoveries ranged from 80.0% to 122.8%. 20 milk and 10 pork samples were analyzed to confirm the performance of the on-site application. The detection results were consistent with the data from LC-MS/MS, indicating the practical reliability of our established assay. The developed LMs-LFIA provides a promising technical support for rapid, sensitive, and on-site detection of DEX.