Sulfamethoxazole degradation by Aeromonas caviae and co-metabolism by the mixed bacteria

Mechanism of microplastics promoting sulfamethoxazole biodegradation in activated sludge as revealed by DNA-stable isotope probing

Microplastics (MPs) often coexist with sulfonamide antibiotics (SAs) in the activated sludge of wastewater treatment plants (WWTPs). Microbial degradation is a crucial pathway for SAs removal in the activated sludge, though its response to MPs still yet to be disclosed. Here, we combined DNA-stable isotope probing (DNA-SIP), PICRUSt and MENA techniques to explore the impact of MPs on the microbial biodegradation of sulfamethoxazole (SMX) in the activated sludge. DNA-SIP revealed 20 genera were responsible for the SMX degradation in the activated sludge, with 13 of these genera being firstly linked with sulfonamide biodegradation. The potential SMX-degrading bacteria showed complex synergistic interaction with the other microbes. Eight degradation pathways were constructed based on the nine identified SMX-related degradation genes. MPs addition enhanced the SMX biodegradation by altering the structure of degrading microbes, increasing their relative abundance and promoting the synergistic interactions between potential SMX-degrading bacteria and other microbes in activated sludge. Besides, genes related to abundant energy production and biofilm formation were involved in SMX degradation in the activated sludge with MPs. Our study reveals the MPs influence on SMX biodegradation in activated sludge, and disclose the potential underlying mechanisms, which will benefit the regulation on antibiotic removal in WWTPs.

Efficient sulfamethoxazole biotransformation and detoxification by newly isolated strain Hydrogenophaga sp. SNF1 via a ring ortho-hydroxylation pathway

Sulfonamides are frequently detected with high concentrations in various environments and was regarded as a serious environmental risk by fostering the dissemination of antibiotic resistance genes. This study for the first time reported a strain SNF1 affiliated with Hydrogenophaga can efficiently degrade sulfamethoxazole (SMX). Strain SNF1 prefers growing under extra carbon sources and neutral condition, and could degrade 500 mg/L SMX completely within 16 h. Under the conditions optimized by response surface method (3.11 g/L NaAc, 0.77 g/L (NH4)2SO4, pH = 7.53, and T = 34.38 ℃), a high removal rate constant 0.5104 /h for 50 mg/L SMX was achieved. Coupling the intermediate products identification with comparative genomic analysis, a novel SMX degradation pathway was proposed. Unlike Actinomycetota degraders, SMX was deaminized and ring ortho-hydroxylated in strain SNF1 using a Rieske dioxygenase in combination with glutamine synthetase system. Rieske dioxygenase gene expression was up-regulated by 1.09 to 6.02-fold in response to 100 mg/L SMX. When SMX is fully degraded, its antimicrobial activity drops by over 90 %, and its anticipated toxicity to aquatic organisms were overall reduced. These findings provided new insights into SMX-degrading microorganisms and mechanisms and highlighted the potential of Hydrogenophaga. sp. SNF1 for biological elimination of SMX from wastewater.

Will the removal of carbon, nitrogen and mixed disinfectants occur simultaneously: The key role of heterotrophic nitrification-aerobic denitrification strain

The capacity and mechanism of heterotrophic nitrification-aerobic denitrification (HNAD) strain (H1) to remove carbon, nitrogen, disinfectants chloroxylenol (PCMX) and benzethonium chloride (BEC) were investigated in this study. PCMX was removed via metabolism and chemical oxygen demand co-metabolism process. BEC was eliminated through bacterial adsorption, which greatly inhibited the removal of other pollutants. Carbon source optimization tests revealed that glucose was the optimal carbon source for co-removal of pollutants under mixed disinfectants circumstances (PCMX + BEC). Comparing the groups without (G1) and with disinfectants (G2), the content of extracellular polymeric substances was higher, and hydrophobicity was enhanced under the hazardous conditions of G2. All the nitrogen metabolism functional genes in G2 were up-regulated, and the electron transport system activity was also improved. At the same time, G2 had lower reactive oxygen species content, which reduced the probability of resistance genes dissemination, but the abundance of most quantified resistance genes was elevated in G2. Toxicity assessment assays found a dramatic reduction in the virulence of G2's effluent compared with the mixed disinfectants. The results confirmed that H1 strain could be used to treat the disinfectant-containing wastewater, which may aid in the application of HNAD process.

Co-metabolism of microorganisms: A study revealing the mechanism of antibiotic removal, progress of biodegradation transformation pathways

The widespread use of antibiotics has resulted in large quantities of antibiotic residues entering aquatic environments, which can lead to the development of antibiotic-resistant bacteria and antibiotic-resistant genes, posing a potential environmental risk and jeopardizing human health. Constructing a microbial co-metabolism system has become an effective measure to improve the removal efficiency of antibiotics by microorganisms. This paper reviews the four main mechanisms involved in microbial removal of antibiotics: bioaccumulation, biosorption, biodegradation and co-metabolism. The promotion of extracellular polymeric substances for biosorption and extracellular degradation and the regulation mechanism of enzymes in biodegradation by microorganisms processes are detailed therein. Transformation pathways for microbial removal of antibiotics are discussed. Bacteria, microalgae, and microbial consortia's roles in antibiotic removal are outlined. The factors influencing the removal of antibiotics by microbial co-metabolism are also discussed. Overall, this review summarizes the current understanding of microbial co-metabolism for antibiotic removal and outlines future research directions.

A microbiome-biochar composite synergistically eliminates the environmental risks of antibiotic mixtures and their toxic byproducts

This study developed a continuous reactor system employing a hybrid hydrogel composite synthesized using a complex sludge microbiome and an adsorbent (HSA). This HSA-based system effectively eliminated the environmental risks associated with a mixture of the antibiotics ciprofloxacin and sulfamethoxazole, which exhibited higher toxicity in combination than individually at environmentally relevant levels. Analytical chemistry experiments revealed the in-situ generation of various byproducts (BPs) within the bioreactor system, with two of these BPs recording toxicity levels that surpassed those of their parent compound. The HSA approach successfully prevented the functional microbiome from being washed out of the reactor, while HSA efficiently removed antibiotic residues in their original and BP forms through synergistic adsorptive and biotransformation mechanisms, ultimately reducing the overall ecotoxicity. The use of HSA thus demonstrates promise not only as a mean to reduce the threat posed by toxic antibiotic residues to aquatic ecosystems but also as a practical solution to operational challenges, such as biomass loss/washout, that are frequently encountered in various environmental bioprocesses.

Synthesis of Silver Nanoparticles from Aeromonas caviae for Antibacterial Activity and In Vivo Effects in Rats

Silver nanoparticles (AgNPs) have excellent antimicrobial properties, as they can inhibit multidrug-resistant (MDR) pathogens. Furthermore, bio-AgNPs have potential applications in medicine due to their low toxicity and high stability. Here, AgNPs were synthesized from the biomass of Aeromonas caviae isolated from a sediment sample and subsequently characterized. The UV-Vis spectra of AgNPs in aqueous medium peaked at 417 nm, matching their plasmon absorption. The X-ray diffraction analysis (XRD) pattern of AgNPs showed four peaks at 2θ values, corresponding to Ag diffraction faces. Absorption band peaks at 3420.16, 1635.54, and 1399.43 cm-1 were identified by Fourier-transform infrared spectroscopy (FTIR) analysis as belonging to functional groups of AgNP-associated biomolecules. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) showed that the nanoparticles are spherical and pseudospherical, with sizes of 15-25 nm. Agar well diffusion minimal inhibitory concentration (MIC) assays were used to assess the antibacterial activity of the nanoparticles against MDR pathogens. AgNPs exhibited antibacterial activity against MDR bacteria. Two groups of albino rats received intraperitoneal injections of AgNPs at 15 mg/kg or 30 mg/kg for 7 days. Blood, kidney, and liver samples were collected to investigate hematological, biochemical, and histopathological alterations. Administered AgNPs in rats fluctuated in liver and kidney function parameters. The ultrastructural impacts of AgNPs were more prominent at higher doses. The results proved the easy, fast, and efficient synthesis of AgNPs using A. caviae isolates and demonstrated the remarkable potential of these AgNPs as antibacterial agents. Nanotoxicological studies are required to identify the specific dose that balances optimal antibacterial activity with minimal toxicity to human health.

Transformation process and phytotoxicity of sulfamethoxazole and N4-acetyl-sulfamethoxazole in rice

Sulfonamide antibiotics, extensively used in human and veterinary therapy, accumulate in agroecosystem soils through livestock manure and sewage irrigation. However, the interaction between sulfonamides and rice plants remains unclear. This study investigated the transformation behavior and toxicity of sulfamethoxazole (SMX) and its main metabolite, N4-acetyl-sulfamethoxazole (NASMX) in rice. SMX and NASMX were rapidly taken up by roots and translocated acropetally. NASMX showed higher accumulating capacity, with NASMX concentrations up to 20.36 ± 1.98 μg/g (roots) and 5.62 ± 1.17 μg/g (shoots), and with SMX concentrations up to 15.97 ± 2.53 μg/g (roots) and 3.22 ± 0.789 μg/g (shoots). A total of 18 intermediate transformation products of SMX were identified by nontarget screening using Orbitrap-HRMS, revealing pathways such as deamination, hydroxylation, acetylation, formylation, and glycosylation. Notably, NASMX transformed back into SMX in rice, a novel finding. Transcriptomic analysis highlights the involvements of cytochrome P450 (CYP450), acetyltransferase (ACEs) and glycosyltransferases (GTs) in these biotransformation pathways. Moreover, exposure to SMX and NASMX disrupts TCA cycle, amino acid, linoleic acid, nucleotide metabolism, and phenylpropanoid biosynthesis pathways of rice, with NASMX exerting a stronger impact on metabolic networks. These findings elucidate the sulfonamides' metabolism, phytotoxicity mechanisms, and contribute to assessing food safety and human exposure risk amid antibiotic pollution.

Bio-degraded of sulfamethoxazole by microbial consortia without addition nutrients: Mineralization, nitrogen removal, and proteomic characterization

Sulfamethoxazole (SMX) is widely employed as an antibiotic, while its residue in environment has become a common public concern. Using 100 mg/L SMX as the sole nutrient source, the acclimated sludge obtained by this study displayed an excellent SMX degradation performance. The addition of SMX resulted in significant microbiological differentiation within the acclimated sludge. Microbacterium (6.6%) was identified as the relatively dominant genera in metabolism group that used SMX as sole carbon source. Highly expressed proteins from this strain strongly suggested its essential role in SMX degradation, while the degradation of SMX by other strains (Thaurea 78%) in co-metabolism group appeared to also rely on this strain. The interactions of differentially expressed proteins were primarily involved in metabolic pathways including TCA cycle and nitrogen metabolism. It is concluded that the sulfonamides might serve not only as the carbon source but also as the nitrogen source in the reactor. A total of 24 intermediates were identified, 13 intermediates were newly reported. The constructed pathway suggested the mineralizing and nitrogen conversion ability towards SMX. Batch experiments also proved that the acclimated sludge displayed ability to biodegrade other sulfonamides, including SM2 and SDZ and SMX-N could be removed completely.

Phytochemical analysis, GC-MS profile and determination of antibacterial, antifungal, anti-inflammatory, antioxidant activities of peel and seeds extracts (chloroform and ethyl acetate) of Tamarindus indica L

Tamarindus indica L., is widely used tree in ayurvedic medicine. Here, we aimed to understand the presence of important constituents in seeds and peel of Tamarind fruits and their biological activities. Hence, seeds and peel of Tamarind fruits are used for further extraction process by soxhlet method (chloroform and ethyl acetate solvents). Results suggest that the ethyl acetate extract (seeds) consists of terpenoids (72.29 ± 0.513 mg/g), phenolic content (68.67 ± 2.11 mg/g) and flavonoids (26.36 ± 2.03 mg/g) whereas chloroform extract (seeds) has terpenoids (42.29 ± 0.98 mg/g). Similarly, chloroform extract (peel) has terpenoids (25.96 ± 3.20 mg/g) and flavonoids (46.36 ± 2.03 mg/g) whereas ethyl acetate extract (peel) has terpenoids (62.93 ± 0.987 mg/g). Furthermore, anti-inflammation activity results revealed that the chloroform extract of peel was found to be more effective with IC50 of 226.14 µg/ml by protein denaturation analysis and with IC50 of 245.5 µg/ml on lipoxygenase inhibition activity. Chloroform extract (peel and seeds) shown better antioxidant activity using DPPH than ethyl acetate extract (peel and seeds). Ethyl acetate extract of seeds showed impressive potency by inhibiting the growth of fungus, Candida albicans. Additionally, ethyl acetate extract of seeds showed impressive potency inhibiting the growth of Escherichia coli than Bacillus cereus. GC-MS analysis shown the existence of diverse set of phytochemicals in each extract. Overall, comparative studies highlight the effectiveness of seeds extracts than peel extracts. Moreover, GC-MS results suggest that the seeds and peel extracts (chloroform and ethyl acetate) contains a wide range of compounds (including flavonoids, isovanillic acid, fatty acids and phenolic compounds) which can be utilized for therapeutic purpose.

Biotransformation of sulfamethoxazole by newly isolated surfactant-producing strain Proteus mirabilis sp. ZXY4: Removal efficiency, pathways, and mechanisms

In this study, the SMX degrading strain Proteus mirabilis sp. ZXY4 with surfactant manufacturing potential was isolated from sludge utilizing blood agar and CTAB agar plate. FTIR analysis indicated that the biosurfactant generated by strain ZXY4 was glycolipid. 3D-EEM demonstrated that SMX biodegradation was strongly connected to biosurfactants, the synergistic effect of biodegradation and biosurfactant made strain ZXY4 have excellent SMX degradation performance. Under the optimal conditions of inoculation dosage of 15%, temperature of 30 ℃, pH of 7 and initial SMX concentration of 5 mg L^-1, strain ZXY4 could completely degrade SMX within 24 h. SMX biodegrades at low concentrations (less than5 mg L^-1) followed by the zero-order kinetic model, high concentration (>5 mg L^-1) is more consistent with the first-order kinetic model. LC-MS analysis revealed 14 SMX degradation intermediates, and five potential biodegradation mechanisms were postulated. The findings provide new insights into the biodegradation of SMX.

Determining the degradation mechanism and application potential of benzopyrene-degrading bacterium Acinetobacter XS-4 by screening

In industrial wastewater treatment, organic pollutants are usually removed by in-situ microorganisms and exogenous bactericides. Benzo [a] pyrene (BaP) is a typical persistent organic pollutant and difficult to be removed. In this study, a new strain of BaP degrading bacteria Acinetobacter XS-4 was obtained and the degradation rate was optimized by response surface method. The results showed that the degradation rate of BaP was 62.73% when pH= 8, substrate concentration was 10 mg/L, temperature was 25 °C, inoculation amount was 15% and culture rate was 180 r/min. Its degradation rate was better than that of the reported degrading bacteria. XS-4 is active in the degradation of BaP. BaP is degraded into phenanthrene by 3, 4-dioxygenase (α subunit and β subunit) in pathway Ⅰ and rapidly forms aldehydes, esters and alkanes. The pathway Ⅱ is realized by the action of salicylic acid hydroxylase. When sodium alginate and polyvinyl alcohol were added to the actual coking wastewater to immobilize XS-4, the degradation rate of BaP was 72.68% after 7 days, and the removal effect was better than that of single BaP wastewater (62.36%), which has the application potential. This study provides theoretical and technical support for microbial degradation of BaP in industrial wastewater.

Comparison of freeze-thaw and sonication cycle-based methods for extracting AMR-associated metabolites from Staphylococcus aureus

Emerging antimicrobial resistance (AMR) among Gram-positive pathogens, specifically in Staphylococcus aureus (S. aureus), is becoming a leading public health concern demanding effective therapeutics. Metabolite modulation can improve the efficacy of existing antibiotics and facilitate the development of effective therapeutics. However, it remained unexplored for drug-resistant S. aureus (gentamicin and methicillin-resistant), primarily due to the dearth of optimal metabolite extraction protocols including a protocol for AMR-associated metabolites. Therefore, in this investigation, we have compared the performance of the two most widely used methods, i.e., freeze-thaw cycle (FTC) and sonication cycle (SC), alone and in combination (FTC + SC), and identified the optimal method for this purpose. A total of 116, 119, and 99 metabolites were identified using the FTC, SC, and FTC + SC methods, respectively, leading to the identification of 163 metabolites cumulatively. Out of 163, 69 metabolites were found to be associated with AMR in published literature consisting of the highest number of metabolites identified by FTC (57) followed by SC (54) and FTC + SC (40). Thus, the performances of FTC and SC methods were comparable with no additional benefits of combining both. Moreover, each method showed biasness toward specific metabolite(s) or class of metabolites, suggesting that the choice of metabolite extraction method shall be decided based on the metabolites of interest in the investigation.