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Xu R, Li L, Zheng J, Ji C, Wu H, Chen X, Chen Y, Hu M, Xu EG, Wang Y. Combined toxic effects of nanoplastics and norfloxacin on mussel: Leveraging biochemical parameters and gut microbiota. THE SCIENCE OF THE TOTAL ENVIRONMENT 2023; 880:163304. [PMID: 37030355 DOI: 10.1016/j.scitotenv.2023.163304] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/29/2022] [Revised: 03/31/2023] [Accepted: 04/01/2023] [Indexed: 05/27/2023]
Abstract
Antibiotics and nanoplastics (NPs) are among the two most concerned and studied marine emerging contaminants in recent years. Given the large number of different types of antibiotics and NPs, there is a need to apply efficient tools to evaluate their combined toxic effects. Using the thick-shelled mussel (Mytilus coruscus) as a marine ecotoxicological model, we applied a battery of fast enzymatic activity assays and 16S rRNA sequencing to investigate the biochemical and gut microbial response of mussels exposed to antibiotic norfloxacin (NOR) and NPs (80 nm polystyrene beads) alone and in combination at environmentally relevant concentrations. After 15 days of exposure, NPs alone significantly inhibited superoxide dismutase (SOD) and amylase (AMS) activities, while catalase (CAT) was affected by both NOR and NPs. The changes in lysozyme (LZM) and lipase (LPS) were increased over time during the treatments. Co-exposure to NPs and NOR significantly affected glutathione (GSH) and trypsin (Typ), which might be explained by the increased bioavailable NOR carried by NPs. The richness and diversity of the gut microbiota of mussels were both decreased by exposures to NOR and NPs, and the top functions of gut microbiota that were affected by the exposures were predicted. The data fast generated by enzymatic test and 16S sequencing allowed further variance and correlation analysis to understand the plausible driving factors and toxicity mechanisms. Despite the toxic effects of only one type of antibiotics and NPs being evaluated, the validated assays on mussels are readily applicable to other antibiotics, NPs, and their mixture.
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Affiliation(s)
- Ran Xu
- International Research Center for Marine Biosciences, College of Fisheries and Life Science at Shanghai Ocean University, Ministry of Science and Technology, Shanghai 201306, China; Key laboratory of Exploration and Utilization of Aquatic Genetic Resources, Ministry of Education, Shanghai Ocean University, Shanghai 201306, China
| | - Li'ang Li
- International Research Center for Marine Biosciences, College of Fisheries and Life Science at Shanghai Ocean University, Ministry of Science and Technology, Shanghai 201306, China; Key laboratory of Exploration and Utilization of Aquatic Genetic Resources, Ministry of Education, Shanghai Ocean University, Shanghai 201306, China
| | - Jiahui Zheng
- International Research Center for Marine Biosciences, College of Fisheries and Life Science at Shanghai Ocean University, Ministry of Science and Technology, Shanghai 201306, China; Key laboratory of Exploration and Utilization of Aquatic Genetic Resources, Ministry of Education, Shanghai Ocean University, Shanghai 201306, China
| | - Chenglong Ji
- CAS Key Laboratory of Coastal Environmental Processes and Ecological Remediation, Yantai Institute of Coastal Zone Research, Chinese Academy of Sciences (CAS), Shandong Key Laboratory of Coastal Environmental Processes, Yantai 264003, China
| | - Huifeng Wu
- CAS Key Laboratory of Coastal Environmental Processes and Ecological Remediation, Yantai Institute of Coastal Zone Research, Chinese Academy of Sciences (CAS), Shandong Key Laboratory of Coastal Environmental Processes, Yantai 264003, China
| | - Xiang Chen
- International Research Center for Marine Biosciences, College of Fisheries and Life Science at Shanghai Ocean University, Ministry of Science and Technology, Shanghai 201306, China; Key laboratory of Exploration and Utilization of Aquatic Genetic Resources, Ministry of Education, Shanghai Ocean University, Shanghai 201306, China
| | - Yuchuan Chen
- International Research Center for Marine Biosciences, College of Fisheries and Life Science at Shanghai Ocean University, Ministry of Science and Technology, Shanghai 201306, China; Key laboratory of Exploration and Utilization of Aquatic Genetic Resources, Ministry of Education, Shanghai Ocean University, Shanghai 201306, China
| | - Menghong Hu
- International Research Center for Marine Biosciences, College of Fisheries and Life Science at Shanghai Ocean University, Ministry of Science and Technology, Shanghai 201306, China; Key laboratory of Exploration and Utilization of Aquatic Genetic Resources, Ministry of Education, Shanghai Ocean University, Shanghai 201306, China
| | - Elvis Genbo Xu
- Department of Biology, University of Southern Denmark, Odense M 5230, Denmark.
| | - Youji Wang
- International Research Center for Marine Biosciences, College of Fisheries and Life Science at Shanghai Ocean University, Ministry of Science and Technology, Shanghai 201306, China; Key laboratory of Exploration and Utilization of Aquatic Genetic Resources, Ministry of Education, Shanghai Ocean University, Shanghai 201306, China.
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Signal Peptidase-Mediated Cleavage of the Anti-σ Factor RsiP at Site 1 Controls σ P Activation and β-Lactam Resistance in Bacillus thuringiensis. mBio 2021; 13:e0370721. [PMID: 35164554 PMCID: PMC8844934 DOI: 10.1128/mbio.03707-21] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/04/2022] Open
Abstract
In Bacillus thuringiensis, β-lactam antibiotic resistance is controlled by the extracytoplasmic function (ECF) σ factor σP. σP activity is inhibited by the anti-σ factor RsiP. In the presence of β-lactam antibiotics, RsiP is degraded and σP is activated. Previous work found that RsiP degradation requires cleavage of RsiP at site 1 by an unknown protease, followed by cleavage at site 2 by the site 2 protease RasP. The penicillin-binding protein PbpP acts as a sensor for β-lactams. PbpP initiates σP activation and is required for site 1 cleavage of RsiP but is not the site 1 protease. Here, we describe the identification of a signal peptidase, SipP, which cleaves RsiP at a site 1 signal peptidase cleavage site and is required for σP activation. Finally, many B. anthracis strains are sensitive to β-lactams yet encode the σP-RsiP signal transduction system. We identified a naturally occurring mutation in the signal peptidase cleavage site of B. anthracis RsiP that renders it resistant to SipP cleavage. We find that B. anthracis RsiP is not degraded in the presence of β-lactams. Altering the B. anthracis RsiP site 1 cleavage site by a single residue to resemble B. thuringiensis RsiP results in β-lactam-dependent degradation of RsiP. We show that mutation of the B. thuringiensis RsiP cleavage site to resemble the sequence of B. anthracis RsiP blocks degradation by SipP. The change in the cleavage site likely explains many reasons why B. anthracis strains are sensitive to β-lactams. IMPORTANCE β-Lactam antibiotics are important for the treatment of many bacterial infections. However, resistance mechanisms have become increasingly more prevalent. Understanding how β-lactam resistance is conferred and how bacteria control expression of β-lactam resistance is important for informing the future treatment of bacterial infections. σP is an alternative σ factor that controls the transcription of genes that confer β-lactam resistance in Bacillus thuringiensis, Bacillus cereus, and Bacillus anthracis. Here, we identify a signal peptidase as the protease required for initiating activation of σP by the degradation of the anti-σ factor RsiP. The discovery that the signal peptidase SipP is required for σP activation highlights an increasing role for signal peptidases in signal transduction, as well as in antibiotic resistance.
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