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Dar MA, Xie R, Zabed HM, Pawar KD, Dhole NP, Sun J. Current paradigms and future challenges in harnessing gut bacterial symbionts of insects for biodegradation of plastic wastes. INSECT SCIENCE 2024. [PMID: 38990171 DOI: 10.1111/1744-7917.13417] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/25/2024] [Revised: 04/30/2024] [Accepted: 05/22/2024] [Indexed: 07/12/2024]
Abstract
The ubiquitous incorporation of plastics into daily life, coupled with inefficient recycling practices, has resulted in the accumulation of millions of metric tons of plastic waste, that poses a serious threat to the Earth's sustainability. Plastic pollution, a global problem, disrupts the ecological balance and endangers various life forms. Efforts to combat plastic pollution are underway, with a promising avenue being biological degradation facilitated by certain insects and their symbiotic gut microorganisms, particularly bacteria. This review consolidates existing knowledge on plastic degradation by insects and their influence on gut microbiota. Additionally, it delves into the potential mechanisms employed by insects in symbiosis with gut bacteria, exploring the bioconversion of waste plastics into value-added biodegradable polymers through mineralization. These insights hold significant promise for the bio-upcycling of plastic waste, opening new horizons for future biomanufacturing of high-value chemicals from plastic-derived compounds. Finally, we weigh the pros and cons of future research endeavors related to the bioprospection of plastic-degrading bacteria from underexplored insect species. We also underscore the importance of bioengineering depolymerases with novel characteristics, aiming for their application in the remediation and valorization of waste plastics.
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Affiliation(s)
- Mudasir A Dar
- Biofuels Institute, School of the Environment and Safety Engineering, Jiangsu University, Zhenjiang, China
- Department of Zoology, Savitribai Phule Pune University, Ganeshkhind, Pune, Maharashtra, India
| | - Rongrong Xie
- Biofuels Institute, School of the Environment and Safety Engineering, Jiangsu University, Zhenjiang, China
| | - Hossain M Zabed
- School of Life Sciences, Guangzhou University, Guangzhou, China
| | - Kiran D Pawar
- School of Nanoscience and Biotechnology, Shivaji University, Vidyanagar, Kolhapur, Maharashtra, India
| | - Neeraja P Dhole
- Department of Zoology, Savitribai Phule Pune University, Ganeshkhind, Pune, Maharashtra, India
| | - Jianzhong Sun
- Biofuels Institute, School of the Environment and Safety Engineering, Jiangsu University, Zhenjiang, China
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2
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Chen C, Song M, Li K, Yan S, Chen M, Geng J. E. coli outer membrane protein T (OmpT) nanopore for peptide sensing. Biochem Biophys Res Commun 2023; 677:132-140. [PMID: 37586211 DOI: 10.1016/j.bbrc.2023.05.125] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2023] [Accepted: 05/31/2023] [Indexed: 08/18/2023]
Abstract
Peptide detection methods with facility and high sensitivity are essential for diagnosing disease associated with peptide biomarkers. Nanopore sensing technology had emerged as a low cost, high-throughput, and scalable tool for peptide detection. The omptins family proteins which can form β-barrel pores have great potentials to be developed as nanopore biosensor. However, there are no study about the channel properties of E. coli OmpT and the development of OmpT as a nanopore biosensor. In this study, the OmpT biological nanopore channel was constructed with a conductance of 1.49 nS in 500 mM NaCl buffer and a three-step gating phenomenon under negative voltage higher than 100 mV and then was developed as a peptide biosensor which can detect peptide without the interfere of ssDNA and dNTPs. The OmpT constructed in this study has potential application in peptide detection, and also provides a new idea for the detection of peptides using the specific binding ability of protease.
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Affiliation(s)
- Chuan Chen
- Department of Laboratory Medicine, State Key Laboratory of Biotherapy and Cancer Center, West China Hospital, Sichuan University and Collaborative Innovation Center, Chengdu, 610041, China; School of Pharmacy, North Sichuan Medical College, Nanchong, 637000, China
| | - Mengxiao Song
- Department of Laboratory Medicine, State Key Laboratory of Biotherapy and Cancer Center, West China Hospital, Sichuan University and Collaborative Innovation Center, Chengdu, 610041, China
| | - Kaiju Li
- Department of Laboratory Medicine, State Key Laboratory of Biotherapy and Cancer Center, West China Hospital, Sichuan University and Collaborative Innovation Center, Chengdu, 610041, China
| | - Shixin Yan
- Department of Laboratory Medicine, State Key Laboratory of Biotherapy and Cancer Center, West China Hospital, Sichuan University and Collaborative Innovation Center, Chengdu, 610041, China
| | - Mutian Chen
- Department of Laboratory Medicine, State Key Laboratory of Biotherapy and Cancer Center, West China Hospital, Sichuan University and Collaborative Innovation Center, Chengdu, 610041, China
| | - Jia Geng
- Department of Laboratory Medicine, State Key Laboratory of Biotherapy and Cancer Center, West China Hospital, Sichuan University and Collaborative Innovation Center, Chengdu, 610041, China; Tianfu Jincheng Laboratory, City of Future Medicine, Chengdu 641400, China.
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3
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Li S, Yang Y, Yang S, Zheng H, Zheng Y, M J, Nagarajan D, Varjani S, Chang JS. Recent advances in biodegradation of emerging contaminants - microplastics (MPs): Feasibility, mechanism, and future prospects. CHEMOSPHERE 2023; 331:138776. [PMID: 37100247 DOI: 10.1016/j.chemosphere.2023.138776] [Citation(s) in RCA: 13] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/13/2023] [Revised: 04/17/2023] [Accepted: 04/22/2023] [Indexed: 05/19/2023]
Abstract
Plastics have become an essential part of life. When it enters the environment, it migrates and breaks down to form smaller size fragments, which are called microplastics (MPs). Compared with plastics, MPs are detrimental to the environment and pose a severe threat to human health. Bioremediation is being recognized as the most environmentally friendly and cost-effective degradation technology for MPs, but knowledge about the biodegradation of MPs is limited. This review explores the various sources of MPs and their migration behavior in terrestrial and aquatic environments. Among the existing MPs removal technologies, biodegradation is considered to be the best removal strategy to alleviate MPs pollution. The biodegradation potential of MPs by bacteria, fungi and algae is discussed. Biodegradation mechanisms such as colonization, fragmentation, assimilation, and mineralization are presented. The effects of MPs characteristics, microbial activity, environmental factors and chemical reagents on biodegradation are analyzed. The susceptibility of microorganisms to MPs toxicity might lead to decreased degradation efficiency, which is also elaborated. The prospects and challenges of biodegradation technologies are discussed. Eliminating prospective bottlenecks is necessary to achieve large-scale bioremediation of MPs-polluted environment. This review provides a comprehensive summary of the biodegradability of MPs, which is crucial for the prudent management of plastic waste.
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Affiliation(s)
- Shuo Li
- College of Chemistry and Chemical Engineering, Qiqihar University, Qiqihar, 161006, China
| | - Yalun Yang
- College of Chemistry and Chemical Engineering, Qiqihar University, Qiqihar, 161006, China
| | - Shanshan Yang
- School of Environment, Harbin Institute of Technology, Harbin, 150090, China; State Key Laboratory of Urban Water Resource and Environment, School of Municipal and Environmental Engineering, Harbin Institute Technology, Harbin, China
| | - Heshan Zheng
- College of Chemistry and Chemical Engineering, Qiqihar University, Qiqihar, 161006, China.
| | - Yongjie Zheng
- College of Chemistry and Chemical Engineering, Qiqihar University, Qiqihar, 161006, China
| | - Jun M
- School of Environment, Harbin Institute of Technology, Harbin, 150090, China
| | - Dillirani Nagarajan
- Department of Chemical Engineering, National Cheng Kung University, Tainan, Taiwan
| | - Sunita Varjani
- School of Energy and Environment, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong
| | - Jo-Shu Chang
- Department of Chemical Engineering, National Cheng Kung University, Tainan, Taiwan; Department of Chemical and Materials Engineering, Tunghai University, Taichung, Taiwan; Research Center for Energy Technology and Strategy, National Cheng Kung University, Tainan, Taiwan; Department of Chemical Engineering and Materials Science, Yuan Ze University, Chung-Li, Taiwan.
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4
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Sun X, Chen Z, Kong T, Chen Z, Dong Y, Kolton M, Cao Z, Zhang X, Zhang H, Liu G, Gao P, Yang N, Lan L, Xu Y, Sun W. Mycobacteriaceae Mineralizes Micropolyethylene in Riverine Ecosystems. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2022; 56:15705-15717. [PMID: 36288260 DOI: 10.1021/acs.est.2c05346] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
Microplastic (MP) contamination is a serious global environmental problem. Plastic contamination has attracted extensive attention during the past decades. While physiochemical weathering may influence the properties of MPs, biodegradation by microorganisms could ultimately mineralize plastics into CO2. Compared to the well-studied marine ecosystems, the MP biodegradation process in riverine ecosystems, however, is less understood. The current study focuses on the MP biodegradation in one of the world's most plastic contaminated rivers, Pearl River, using micropolyethylene (mPE) as a model substrate. Mineralization of 13C-labeled mPE into 13CO2 provided direct evidence of mPE biodegradation by indigenous microorganisms. Several Actinobacteriota genera were identified as putative mPE degraders. Furthermore, two Mycobacteriaceae isolates related to the putative mPE degraders, Mycobacterium sp. mPE3 and Nocardia sp. mPE12, were retrieved, and their ability to mineralize 13C-mPE into 13CO2 was confirmed. Pangenomic analysis reveals that the genes related to the proposed mPE biodegradation pathway are shared by members of Mycobacteriaceae. While both Mycobacterium and Nocardia are known for their pathogenicity, these populations on the plastisphere in this study were likely nonpathogenic as they lacked virulence factors. The current study provided direct evidence for MP mineralization by indigenous biodegraders and predicted their biodegradation pathway, which may be harnessed to improve bioremediation of MPs in urban rivers.
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Affiliation(s)
- Xiaoxu Sun
- National-Regional Joint Engineering Research Center for Soil Pollution Control and Remediation in South China, Guangdong Key Laboratory of Integrated Agro-environmental Pollution Control and Management, Institute of Eco-environmental and Soil Sciences, Guangdong Academy of Sciences, Guangzhou 510650, P. R. China
- Guangdong-Hong Kong-Macao Joint Laboratory for Environmental Pollution and Control, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China
| | - Zhenyu Chen
- National-Regional Joint Engineering Research Center for Soil Pollution Control and Remediation in South China, Guangdong Key Laboratory of Integrated Agro-environmental Pollution Control and Management, Institute of Eco-environmental and Soil Sciences, Guangdong Academy of Sciences, Guangzhou 510650, P. R. China
- Guangdong-Hong Kong-Macao Joint Laboratory for Environmental Pollution and Control, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China
- School of Environment, Key Laboratory of Yellow River and Huai River Water Environment and Pollution Control, Ministry of Education, Henan Normal University, Xinxiang 453007, China
| | - Tianle Kong
- National-Regional Joint Engineering Research Center for Soil Pollution Control and Remediation in South China, Guangdong Key Laboratory of Integrated Agro-environmental Pollution Control and Management, Institute of Eco-environmental and Soil Sciences, Guangdong Academy of Sciences, Guangzhou 510650, P. R. China
- Guangdong-Hong Kong-Macao Joint Laboratory for Environmental Pollution and Control, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China
- College of Environmental Science and Engineering, Donghua University, Shanghai 201620, China
| | - Zheng Chen
- Department of Health and Environmental Sciences, Xi'an Jiaotong-Liverpool University, Suzhou 215123, China
| | - Yiran Dong
- School of Environmental Studies, China University of Geosciences (Wuhan), Wuhan 430074, China
| | - Max Kolton
- National-Regional Joint Engineering Research Center for Soil Pollution Control and Remediation in South China, Guangdong Key Laboratory of Integrated Agro-environmental Pollution Control and Management, Institute of Eco-environmental and Soil Sciences, Guangdong Academy of Sciences, Guangzhou 510650, P. R. China
- Guangdong-Hong Kong-Macao Joint Laboratory for Environmental Pollution and Control, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China
- French Associates Institute for Agriculture and Biotechnology of Drylands, Ben-Gurion University of the Negev, Beer Sheva 849900, Israel
| | - Zhiguo Cao
- School of Environment, Key Laboratory of Yellow River and Huai River Water Environment and Pollution Control, Ministry of Education, Henan Normal University, Xinxiang 453007, China
| | - Xin Zhang
- School of Environment, Key Laboratory of Yellow River and Huai River Water Environment and Pollution Control, Ministry of Education, Henan Normal University, Xinxiang 453007, China
| | - Haihan Zhang
- School of Environmental and Municipal Engineering, Xi'an University of Architecture and Technology, Xi'an 710055, China
| | - Guoqiang Liu
- Guangdong Key Laboratory of Environmental Pollution and Health, School of Environment, Jinan University, Guangzhou 511443, China
| | - Pin Gao
- National-Regional Joint Engineering Research Center for Soil Pollution Control and Remediation in South China, Guangdong Key Laboratory of Integrated Agro-environmental Pollution Control and Management, Institute of Eco-environmental and Soil Sciences, Guangdong Academy of Sciences, Guangzhou 510650, P. R. China
- Guangdong-Hong Kong-Macao Joint Laboratory for Environmental Pollution and Control, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China
- College of Environmental Science and Engineering, Donghua University, Shanghai 201620, China
| | - Nie Yang
- National-Regional Joint Engineering Research Center for Soil Pollution Control and Remediation in South China, Guangdong Key Laboratory of Integrated Agro-environmental Pollution Control and Management, Institute of Eco-environmental and Soil Sciences, Guangdong Academy of Sciences, Guangzhou 510650, P. R. China
- Guangdong-Hong Kong-Macao Joint Laboratory for Environmental Pollution and Control, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China
- College of Environmental Science and Engineering, Donghua University, Shanghai 201620, China
| | - Ling Lan
- National-Regional Joint Engineering Research Center for Soil Pollution Control and Remediation in South China, Guangdong Key Laboratory of Integrated Agro-environmental Pollution Control and Management, Institute of Eco-environmental and Soil Sciences, Guangdong Academy of Sciences, Guangzhou 510650, P. R. China
- Guangdong-Hong Kong-Macao Joint Laboratory for Environmental Pollution and Control, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China
| | - Yating Xu
- National-Regional Joint Engineering Research Center for Soil Pollution Control and Remediation in South China, Guangdong Key Laboratory of Integrated Agro-environmental Pollution Control and Management, Institute of Eco-environmental and Soil Sciences, Guangdong Academy of Sciences, Guangzhou 510650, P. R. China
- Guangdong-Hong Kong-Macao Joint Laboratory for Environmental Pollution and Control, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China
| | - Weimin Sun
- National-Regional Joint Engineering Research Center for Soil Pollution Control and Remediation in South China, Guangdong Key Laboratory of Integrated Agro-environmental Pollution Control and Management, Institute of Eco-environmental and Soil Sciences, Guangdong Academy of Sciences, Guangzhou 510650, P. R. China
- Guangdong-Hong Kong-Macao Joint Laboratory for Environmental Pollution and Control, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China
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Structure, regulation, and host interaction of outer membrane protein U (OmpU) of Vibrio species. Microb Pathog 2021; 162:105267. [PMID: 34718127 DOI: 10.1016/j.micpath.2021.105267] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2021] [Revised: 09/30/2021] [Accepted: 10/20/2021] [Indexed: 01/22/2023]
Abstract
OmpU is a multimeric, cation selective outer membrane protein of Vibrio and related species that non-covalently interact with peptidoglycan layer. Interaction of OmpU with human host cells triggers signaling pathways to promote cytokine secretion, reactive oxygen species production, and caspase independent death in immune and epithelial cells. Non-choleric OmpU imparts resistance to antimicrobial peptides and induces actin cytoskeletal reorganization in the host cells. Further, OmpU isolated from Vibrio species elicits an immune response in several aquaculture hosts. Importantly, in-vivo studies using recombinant OmpU or OmpU derived mimotopes reveal a short-lasting immunity, and protection against Vibrio in the aquaculture sector. In conclusion, OmpU is a key adhesion protein and an important virulence factor for successful colonization of Vibrio species into hosts. This review article provides a broad overview of structural, regulatory, and functional mechanisms of OmpU in normal and disease states.
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Amobonye A, Bhagwat P, Singh S, Pillai S. Plastic biodegradation: Frontline microbes and their enzymes. THE SCIENCE OF THE TOTAL ENVIRONMENT 2021; 759:143536. [PMID: 33190901 DOI: 10.1016/j.scitotenv.2020.143536] [Citation(s) in RCA: 173] [Impact Index Per Article: 57.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/14/2020] [Revised: 10/16/2020] [Accepted: 10/17/2020] [Indexed: 05/07/2023]
Abstract
Plastic polymers with different properties have been developed in the last 150 years to replace materials such as wood, glass and metals across various applications. Nevertheless, the distinct properties which make plastic desirable for our daily use also threaten our planet's sustainability. Plastics are resilient, non-reactive and most importantly, non-biodegradable. Hence, there has been an exponential increase in plastic waste generation, which has since been recognised as a global environmental threat. Plastic wastes have adversely affected life on earth, primarily through their undesirable accumulation in landfills, leaching into the soil, increased greenhouse gas emission, etc. Even more damaging is their impact on the aquatic ecosystems as they cause entanglement, ingestion and intestinal blockage in aquatic animals. Furthermore, plastics, especially in the microplastic form, have also been found to interfere with chemical interaction between marine organisms, to cause intrinsic toxicity by leaching, and by absorbing persistent organic contaminants as well as pathogens. The current methods for eliminating these wastes (incineration, landfilling, and recycling) come at massive costs, are unsustainable, and put more burden on our environment. Thus, recent focus has been placed more on the potential of biological systems to degrade synthetic plastics. In this regard, some insects, bacteria and fungi have been shown to ingest these polymers and convert them into environmentally friendly carbon compounds. Hence, in the light of recent literature, this review emphasises the multifaceted roles played by microorganisms in this process. The current understanding of the roles played by actinomycetes, algae, bacteria, fungi and their enzymes in enhancing the degradation of synthetic plastics are reviewed, with special focus on their modes of action and probable enzymatic mechanisms. Besides, key areas for further exploration, such as the manipulation of microorganisms through molecular cloning, modification of enzymatic characteristics and metabolic pathway design, are also highlighted.
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Affiliation(s)
- Ayodeji Amobonye
- Department of Biotechnology and Food Technology, Faculty of Applied Sciences, Durban University of Technology, P.O. Box 1334, Durban 4000, South Africa.
| | - Prashant Bhagwat
- Department of Biotechnology and Food Technology, Faculty of Applied Sciences, Durban University of Technology, P.O. Box 1334, Durban 4000, South Africa.
| | - Suren Singh
- Department of Biotechnology and Food Technology, Faculty of Applied Sciences, Durban University of Technology, P.O. Box 1334, Durban 4000, South Africa.
| | - Santhosh Pillai
- Department of Biotechnology and Food Technology, Faculty of Applied Sciences, Durban University of Technology, P.O. Box 1334, Durban 4000, South Africa.
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Ducarmon QR, Zwittink RD, Hornung BVH, van Schaik W, Young VB, Kuijper EJ. Gut Microbiota and Colonization Resistance against Bacterial Enteric Infection. Microbiol Mol Biol Rev 2019; 83:e00007-19. [PMID: 31167904 PMCID: PMC6710460 DOI: 10.1128/mmbr.00007-19] [Citation(s) in RCA: 241] [Impact Index Per Article: 48.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
The gut microbiome is critical in providing resistance against colonization by exogenous microorganisms. The mechanisms via which the gut microbiota provide colonization resistance (CR) have not been fully elucidated, but they include secretion of antimicrobial products, nutrient competition, support of gut barrier integrity, and bacteriophage deployment. However, bacterial enteric infections are an important cause of disease globally, indicating that microbiota-mediated CR can be disturbed and become ineffective. Changes in microbiota composition, and potential subsequent disruption of CR, can be caused by various drugs, such as antibiotics, proton pump inhibitors, antidiabetics, and antipsychotics, thereby providing opportunities for exogenous pathogens to colonize the gut and ultimately cause infection. In addition, the most prevalent bacterial enteropathogens, including Clostridioides difficile, Salmonella enterica serovar Typhimurium, enterohemorrhagic Escherichia coli, Shigella flexneri, Campylobacter jejuni, Vibrio cholerae, Yersinia enterocolitica, and Listeria monocytogenes, can employ a wide array of mechanisms to overcome colonization resistance. This review aims to summarize current knowledge on how the gut microbiota can mediate colonization resistance against bacterial enteric infection and on how bacterial enteropathogens can overcome this resistance.
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Affiliation(s)
- Q R Ducarmon
- Center for Microbiome Analyses and Therapeutics, Leiden University Medical Center, Leiden, Netherlands
- Experimental Bacteriology, Department of Medical Microbiology, Leiden University Medical Center, Leiden, Netherlands
| | - R D Zwittink
- Center for Microbiome Analyses and Therapeutics, Leiden University Medical Center, Leiden, Netherlands
- Experimental Bacteriology, Department of Medical Microbiology, Leiden University Medical Center, Leiden, Netherlands
| | - B V H Hornung
- Center for Microbiome Analyses and Therapeutics, Leiden University Medical Center, Leiden, Netherlands
- Experimental Bacteriology, Department of Medical Microbiology, Leiden University Medical Center, Leiden, Netherlands
| | - W van Schaik
- Institute of Microbiology and Infection, University of Birmingham, Birmingham, United Kingdom
| | - V B Young
- Department of Microbiology and Immunology, University of Michigan, Ann Arbor, Michigan, USA
- Department of Internal Medicine/Infectious Diseases Division, University of Michigan Medical Center, Ann Arbor, Michigan, USA
| | - E J Kuijper
- Center for Microbiome Analyses and Therapeutics, Leiden University Medical Center, Leiden, Netherlands
- Experimental Bacteriology, Department of Medical Microbiology, Leiden University Medical Center, Leiden, Netherlands
- Clinical Microbiology Laboratory, Department of Medical Microbiology, Leiden University Medical Center, Leiden, Netherlands
- Netherlands Donor Feces Bank, Leiden, Netherlands
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8
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Ramírez-Carreto S, Pérez-García EI, Salazar-García SI, Bernáldez-Sarabia J, Licea-Navarro A, Rudiño-Piñera E, Pérez-Martínez L, Pedraza-Alva G, Rodríguez-Almazán C. Identification of a pore-forming protein from sea anemone Anthopleura dowii Verrill (1869) venom by mass spectrometry. J Venom Anim Toxins Incl Trop Dis 2019; 25:e147418. [PMID: 31131002 PMCID: PMC6483413 DOI: 10.1590/1678-9199-jvatitd-1474-18] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2018] [Accepted: 11/13/2018] [Indexed: 12/14/2022] Open
Abstract
Background: Pore-forming proteins (PFP) are a class of toxins abundant in the venom of
sea anemones. Owing to their ability to recognize and permeabilize cell
membranes, pore-forming proteins have medical potential in cancer therapy or
as biosensors. In the present study, we showed the partial purification and
sequencing of a pore-forming protein from Anthopleura dowii
Verrill (1869). 17. Methods: Cytolytic activity of A. dowii Verrill (1869) venom was
determined via hemolysis assay in the erythrocytes of four mammals (sheep,
goat, human and rabbit). The cytotoxic activity was analyzed in the human
adherent lung carcinoma epithelial cells (A549) by the cytosolic lactate
dehydrogenase (LDH) assay, and trypan blue staining. The venom was
fractionated via ammonium sulfate precipitation gradient, dialysis, and ion
exchange chromatography. The presence of a pore-forming protein in purified
fractions was evaluated through hemolytic and cytotoxic assays, and the
activity fraction was analyzed using the percent of osmotic protections
after polyethylene glycol (PEG) treatment and mass spectrometry. 18. Results: The amount of protein at which the venom produced 50% hemolysis
(HU50) was determined in hemolysis assays using erythrocytes
from sheep (HU50 = 10.7 ± 0.2 μg), goat (HU50 = 13.2 ±
0.3 μg), rabbit (HU50 = 34.7 ± 0.5 μg), and human
(HU50 = 25.6 ± 0.6 μg). The venom presented a cytotoxic
effect in A549 cells and the protein amount present in the venom responsible
for producing 50% death (IC50) was determined using a trypan blue
cytotoxicity assay (1.84 ± 0.40 μg/mL). The loss of membrane integrity in
the A549 cells caused by the venom was detected by the release of LDH in
proportion to the amount of protein. The venom was fractionated; and the
fraction with hemolytic and cytotoxic activities was analyzed by mass
spectrometry. A pore-forming protein was identified. The cytotoxicity in the
A549 cells produced by the fraction containing the pore-forming protein was
osmotically protected by PEG-3350 Da molecular mass, which corroborated that
the loss of integrity in the plasma membrane was produced via pore
formation. 19. Conclusion: A. dowii Verrill (1869) venom
contains a pore-forming protein suitable for designing new drugs for cancer
therapy.
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Affiliation(s)
- Santos Ramírez-Carreto
- Universidad Nacional Autónoma de México, Instituto de Biotecnología, Departamento de Medicina Molecular y Bioprocesos, Av. Universidad 2001, Cuernavaca, Morelos, México
| | - Erick I Pérez-García
- Universidad Nacional Autónoma de México, Instituto de Biotecnología, Departamento de Medicina Molecular y Bioprocesos, Av. Universidad 2001, Cuernavaca, Morelos, México
| | - Sandra I Salazar-García
- Universidad Nacional Autónoma de México, Instituto de Biotecnología, Departamento de Medicina Molecular y Bioprocesos, Av. Universidad 2001, Cuernavaca, Morelos, México
| | - Johanna Bernáldez-Sarabia
- Centro de Investigación Científica y de Educación Superior de Ensenada, Departamento de Innovación Biomédica, Baja California, México
| | - Alexei Licea-Navarro
- Centro de Investigación Científica y de Educación Superior de Ensenada, Departamento de Innovación Biomédica, Baja California, México
| | - Enrique Rudiño-Piñera
- Universidad Nacional Autónoma de México, Instituto de Biotecnología, Departamento de Medicina Molecular y Bioprocesos, Av. Universidad 2001, Cuernavaca, Morelos, México
| | - Leonor Pérez-Martínez
- Universidad Nacional Autónoma de México, Instituto de Biotecnología, Departamento de Medicina Molecular y Bioprocesos, Av. Universidad 2001, Cuernavaca, Morelos, México
| | - Gustavo Pedraza-Alva
- Universidad Nacional Autónoma de México, Instituto de Biotecnología, Departamento de Medicina Molecular y Bioprocesos, Av. Universidad 2001, Cuernavaca, Morelos, México
| | - Claudia Rodríguez-Almazán
- Universidad Nacional Autónoma de México, Instituto de Biotecnología, Departamento de Medicina Molecular y Bioprocesos, Av. Universidad 2001, Cuernavaca, Morelos, México
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Unusual Constriction Zones in the Major Porins OmpU and OmpT from Vibrio cholerae. Structure 2018; 26:708-721.e4. [PMID: 29657131 DOI: 10.1016/j.str.2018.03.010] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2017] [Revised: 02/15/2018] [Accepted: 03/16/2018] [Indexed: 01/26/2023]
Abstract
The outer membranes (OM) of many Gram-negative bacteria contain general porins, which form nonspecific, large-diameter channels for the diffusional uptake of small molecules required for cell growth and function. While the porins of Enterobacteriaceae (e.g., E. coli OmpF and OmpC) have been extensively characterized structurally and biochemically, much less is known about their counterparts in Vibrionaceae. Vibrio cholerae, the causative agent of cholera, has two major porins, OmpU and OmpT, for which no structural information is available despite their importance for the bacterium. Here we report high-resolution X-ray crystal structures of V. cholerae OmpU and OmpT complemented with molecular dynamics simulations. While similar overall to other general porins, the channels of OmpU and OmpT have unusual constrictions that create narrower barriers for small-molecule permeation and change the internal electric fields of the channels. Together with electrophysiological and in vitro transport data, our results illuminate small-molecule uptake within the Vibrionaceae.
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Li H, Zhang W, Dong C. Crystal structure of the outer membrane protein OmpU from Vibrio cholerae at 2.2 Å resolution. Acta Crystallogr D Struct Biol 2018; 74:21-29. [PMID: 29372896 PMCID: PMC5786005 DOI: 10.1107/s2059798317017697] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2017] [Accepted: 12/12/2017] [Indexed: 11/29/2022] Open
Abstract
Vibrio cholerae causes a severe disease that kills thousands of people annually. The outer membrane protein OmpU is the most abundant outer membrane protein in V. cholerae, and has been identified as an important virulence factor that is involved in host-cell interaction and recognition, as well as being critical for the survival of the pathogenic V. cholerae in the host body and in harsh environments. The mechanism of these processes is not well understood owing to a lack of the structure of V. cholerae OmpU. Here, the crystal structure of the V. cholerae OmpU trimer is reported to a resolution of 2.2 Å. The protomer forms a 16-β-stranded barrel with a noncanonical N-terminal coil located in the lumen of the barrel that consists of residues Gly32-Ser42 and is observed to participate in forming the second gate in the pore. By mapping the published functional data onto the OmpU structure, the OmpU structure reinforces the notion that the long extracellular loop L4 with a β-hairpin-like motif may be critical for host-cell binding and invasion, while L3, L4 and L8 are crucially implicated in phage recognition by V. cholerae.
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Affiliation(s)
- Huanyu Li
- Biomedical Research Centre, Norwich Medical School, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, England
| | - Weijiao Zhang
- Biomedical Research Centre, Norwich Medical School, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, England
| | - Changjiang Dong
- Biomedical Research Centre, Norwich Medical School, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, England
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Bina XR, Howard MF, Ante VM, Bina JE. Vibrio cholerae LeuO Links the ToxR Regulon to Expression of Lipid A Remodeling Genes. Infect Immun 2016; 84:3161-3171. [PMID: 27550934 PMCID: PMC5067749 DOI: 10.1128/iai.00445-16] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2016] [Accepted: 08/14/2016] [Indexed: 11/20/2022] Open
Abstract
Vibrio cholerae is an intestinal pathogen that causes the diarrheal disease cholera. Colonization of the intestine depends upon the expression of genes that allow V. cholerae to overcome host barriers, including low pH, bile acids, and the innate immune system. ToxR is a major contributor to this process. ToxR is a membrane-spanning transcription factor that coordinates gene expression in response to environmental cues. In previous work we showed that ToxR upregulated leuO expression in response to bile salts. LeuO is a LysR family transcription factor that contributes to acid tolerance, bile resistance, and biofilm formation in V. cholerae Here, we investigated the function of ToxR and LeuO in cationic antimicrobial peptide (CAMP) resistance. We report that ToxR and LeuO contribute to CAMP resistance by regulating carRS transcription. CarRS is a two-component regulatory system that positively regulates almEFG expression. AlmEFG confers CAMP resistance by glycinylation of lipid A. We found that the expression of carRS and almEFG and the polymyxin B MIC increased in mutants lacking toxRS or leuO Conversely, leuO overexpression decreased the polymyxin B MIC. Furthermore, we found that LeuO directly bound to the carRS promoter and that ToxR-dependent activation of leuO transcription regulated carRS transcription in response to bile salts. Our results suggest that LeuO functions downstream of ToxR to modulate carRS expression in response to environmental cues. This study extends the functional role of ToxR and LeuO in environmental adaptation to include cell surface remodeling and CAMP resistance.
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Affiliation(s)
- X Renee Bina
- University of Pittsburgh School of Medicine, Department of Microbiology and Molecular Genetics, Pittsburgh, Pennsylvania, USA
| | - Mondraya F Howard
- University of Pittsburgh School of Medicine, Department of Microbiology and Molecular Genetics, Pittsburgh, Pennsylvania, USA
| | - Vanessa M Ante
- University of Pittsburgh School of Medicine, Department of Microbiology and Molecular Genetics, Pittsburgh, Pennsylvania, USA
| | - James E Bina
- University of Pittsburgh School of Medicine, Department of Microbiology and Molecular Genetics, Pittsburgh, Pennsylvania, USA
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12
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Abstract
UNLABELLED ToxR is a major virulence gene regulator in Vibrio cholerae. Although constitutively expressed under many laboratory conditions, our previous work demonstrated that the level of ToxR increases significantly when cells are grown in the presence of the 4 amino acids asparagine, arginine, glutamate, and serine (NRES). We show here that the increase in ToxR production in response to NRES requires the Var/Csr global regulatory circuit. The VarS/VarA two-component system controls the amount of active CsrA, a small RNA-binding protein involved in the regulation of a wide range of cellular processes. Our data show that a varA mutant, which is expected to overproduce active CsrA, had elevated levels of ToxR in the absence of the NRES stimulus. Conversely, specific amino acid substitutions in CsrA were associated with defects in ToxR production in response to NRES. These data indicate that CsrA is a positive regulator of ToxR levels. Unlike previously described effects of CsrA on virulence gene regulation, the effects of CsrA on ToxR were not mediated through quorum sensing and HapR. CsrA is likely essential in V. cholerae, since a complete deletion of csrA was not possible; however, point mutations in CsrA were tolerated well. The CsrA Arg6His mutant had wild-type growth in vitro but was severely attenuated in the infant mouse model of V. cholerae infection, showing that CsrA is critical for pathogenesis. This study has broad implications for our understanding of how V. cholerae integrates its response to environmental cues with the regulation of important virulence genes. IMPORTANCE In order to colonize the human host, Vibrio cholerae must sense and respond to environmental signals to ensure appropriate expression of genes required for pathogenesis. Uncovering how V. cholerae senses its environment and activates its virulence gene repertoire is critical for our understanding of how V. cholerae transitions from its natural aquatic habitat to the human host. Here we demonstrate a previously unknown link between the global regulator CsrA and the major V. cholerae virulence gene regulator ToxR. The role of CsrA in the cell is to receive input from the environment and coordinate an appropriate cellular response. By linking environmental sensing to the ToxR regulon, CsrA effectively acts as a switch that controls pathogenesis in response to specific signals. We demonstrate that CsrA is critical for virulence in the infant mouse model of V. cholerae infection, consistent with its role as an in vivo regulator of virulence gene expression.
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13
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Pittel I, Alper N, Yonai S, Basch S, Blum L, Bachur A, Paas Y. Computational and biochemical design of a nanopore cleavable by a cancer-secreted enzyme. Chembiochem 2015; 16:463-71. [PMID: 25581099 DOI: 10.1002/cbic.201402378] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2014] [Indexed: 11/11/2022]
Abstract
Many proteinaceous macromolecules selectively transport substrates across lipid bilayers and effectively serve as gated nanopores. Here, we engineered cleavage-site motifs for human matrix metalloprotease 7 (MMP-7) into the extracellular and pore-constricting loops of OprD, a bacterial substrate-specific transmembrane channel. Concurrent removal of two extracellular loops allowed MMP-7 to access and hydrolyze a cleavage-site motif engineered within the pore's major constricting loop, in both membrane-incorporated and detergent-solubilized OprDs. Import of antibiotics by the engineered OprDs into living bacteria pointed to their proper folding and integration in biological membranes. Purified engineered OprDs were also found to be properly folded in detergent. Hence, this study demonstrates the design of nanopores with a constriction cleavable by tumor-secreted enzymes (like MMP-7) for their potential incorporation in lipid-based nanoparticles to accelerate drug release at the tumor site.
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Affiliation(s)
- Ilya Pittel
- Laboratory of Ion Channels, The Mina and Everard Goodman Faculty of Life Sciences, The Institute of Nanotechnology and Advanced Materials, Bar-Ilan University, Ramat Gan 52900 (Israel)
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14
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Goulart CL, Bisch PM, von Krüger WMA, Homblé F. VCA1008: An Anion-Selective Porin of Vibrio Cholerae. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2014; 1848:680-7. [PMID: 25462170 DOI: 10.1016/j.bbamem.2014.11.009] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/15/2014] [Revised: 11/05/2014] [Accepted: 11/10/2014] [Indexed: 01/14/2023]
Abstract
A putative porin function has been assigned to VCA1008 of Vibrio cholerae. Its coding gene, vca1008, is expressed upon colonization of the small intestine in infant mice and human volunteers, and is essential for infection. In vitro, vca1008 is expressed under inorganic phosphate limitation and, in this condition, VCA1008 is the major outer membrane protein of the bacterium. Here, we provide the first functional characterization of VCA1008 reconstituted into planar lipid bilayers. Our main findings were: 1) VCA1008 forms an ion channel that, at high voltage (~±100 mV), presents a voltage-dependent activity and displays closures typical of trimeric porins, with a conductance of 4.28±0.04 nS (n=164) in 1M KCl; 2) It has a preferred selectivity for anions over cations; 3) Its conductance saturates with increasing inorganic phosphate concentration, suggesting VCA1008 contains binding site(s) for this anion; 4) Its ion selectivity is controlled by both fixed charged residues within the channel and diffusion along the pore; 5) Partitioning of poly (ethylene glycol)s (PEGs) of different molecular mass suggests that VCA1008 channel has a pore exclusion limit of 0.9 nm.
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Affiliation(s)
- Carolina L Goulart
- Structure et Fonction des Membranes Biologiques, Centre de Biologie Structurale et de Bioinformatique, Faculté des Sciences, Université Libre de Bruxelles, Campus Plaine (CP 206/2), B - 1050 Brussels, Belgium
| | - Paulo M Bisch
- Laboratório de Física Biológica, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
| | - Wanda M A von Krüger
- Laboratório de Física Biológica, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
| | - Fabrice Homblé
- Structure et Fonction des Membranes Biologiques, Centre de Biologie Structurale et de Bioinformatique, Faculté des Sciences, Université Libre de Bruxelles, Campus Plaine (CP 206/2), B - 1050 Brussels, Belgium.
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Affiliation(s)
| | - Sergey M. Bezrukov
- Program in Physical Biology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, U.S.A
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Niedzwiecki D, Mohammad M, Movileanu L. Inspection of the engineered FhuA ΔC/Δ4L protein nanopore by polymer exclusion. Biophys J 2012; 103:2115-24. [PMID: 23200045 PMCID: PMC3512039 DOI: 10.1016/j.bpj.2012.10.008] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2012] [Revised: 10/03/2012] [Accepted: 10/10/2012] [Indexed: 12/11/2022] Open
Abstract
Extensive engineering of protein nanopores for biotechnological applications using native scaffolds requires further inspection of their internal geometry and size. Recently, we redesigned ferric hydroxamate uptake component A (FhuA), a 22-β-stranded protein containing an N-terminal 160-residue cork domain (C). The cork domain and four large extracellular loops (4L) were deleted to obtain an unusually stiff engineered FhuA ΔC/Δ4L nanopore. We employed water-soluble poly(ethylene glycols) and dextran polymers to examine the interior of FhuA ΔC/Δ4L. When this nanopore was reconstituted into a synthetic planar lipid bilayer, addition of poly(ethylene glycols) produced modifications in the single-channel conductance, allowing for the evaluation of the nanopore diameter. Here, we report that FhuA ΔC/Δ4L features an approximate conical internal geometry with the cis entrance smaller than the trans entrance, in accord with the asymmetric nature of the crystal structure of the wild-type FhuA protein. Further experiments with impermeable dextran polymers indicated an average internal diameter of ~2.4 nm, a conclusion we arrived at based upon the polymer-induced alteration of the access resistance contribution to the nanopore's total resistance. Molecular insights inferred from this work represent a platform for future protein engineering of FhuA that will be employed for specific tasks in biotechnological applications.
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Affiliation(s)
| | | | - Liviu Movileanu
- Department of Physics, Syracuse University, Syracuse, New York
- Structural Biology, Biochemistry, and Biophysics Program, Syracuse University, Syracuse, New York
- Syracuse Biomaterials Institute, Syracuse University, Syracuse, New York
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Handy RD, van den Brink N, Chappell M, Mühling M, Behra R, Dušinská M, Simpson P, Ahtiainen J, Jha AN, Seiter J, Bednar A, Kennedy A, Fernandes TF, Riediker M. Practical considerations for conducting ecotoxicity test methods with manufactured nanomaterials: what have we learnt so far? ECOTOXICOLOGY (LONDON, ENGLAND) 2012; 21:933-72. [PMID: 22422174 PMCID: PMC3325413 DOI: 10.1007/s10646-012-0862-y] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 01/28/2012] [Indexed: 05/18/2023]
Abstract
This review paper reports the consensus of a technical workshop hosted by the European network, NanoImpactNet (NIN). The workshop aimed to review the collective experience of working at the bench with manufactured nanomaterials (MNMs), and to recommend modifications to existing experimental methods and OECD protocols. Current procedures for cleaning glassware are appropriate for most MNMs, although interference with electrodes may occur. Maintaining exposure is more difficult with MNMs compared to conventional chemicals. A metal salt control is recommended for experiments with metallic MNMs that may release free metal ions. Dispersing agents should be avoided, but if they must be used, then natural or synthetic dispersing agents are possible, and dispersion controls essential. Time constraints and technology gaps indicate that full characterisation of test media during ecotoxicity tests is currently not practical. Details of electron microscopy, dark-field microscopy, a range of spectroscopic methods (EDX, XRD, XANES, EXAFS), light scattering techniques (DLS, SLS) and chromatography are discussed. The development of user-friendly software to predict particle behaviour in test media according to DLVO theory is in progress, and simple optical methods are available to estimate the settling behaviour of suspensions during experiments. However, for soil matrices such simple approaches may not be applicable. Alternatively, a Critical Body Residue approach may be taken in which body concentrations in organisms are related to effects, and toxicity thresholds derived. For microbial assays, the cell wall is a formidable barrier to MNMs and end points that rely on the test substance penetrating the cell may be insensitive. Instead assays based on the cell envelope should be developed for MNMs. In algal growth tests, the abiotic factors that promote particle aggregation in the media (e.g. ionic strength) are also important in providing nutrients, and manipulation of the media to control the dispersion may also inhibit growth. Controls to quantify shading effects, and precise details of lighting regimes, shaking or mixing should be reported in algal tests. Photosynthesis may be more sensitive than traditional growth end points for algae and plants. Tests with invertebrates should consider non-chemical toxicity from particle adherence to the organisms. The use of semi-static exposure methods with fish can reduce the logistical issues of waste water disposal and facilitate aspects of animal husbandry relevant to MMNs. There are concerns that the existing bioaccumulation tests are conceptually flawed for MNMs and that new test(s) are required. In vitro testing strategies, as exemplified by genotoxicity assays, can be modified for MNMs, but the risk of false negatives in some assays is highlighted. In conclusion, most protocols will require some modifications and recommendations are made to aid the researcher at the bench.
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Affiliation(s)
- Richard D Handy
- Ecotoxicology Research and Innovation Centre, School of Biomedical & Biological Sciences, University of Plymouth, Plymouth, UK.
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Effects of amino acid supplementation on porin expression and ToxR levels in Vibrio cholerae. Infect Immun 2011; 80:518-28. [PMID: 22144480 DOI: 10.1128/iai.05851-11] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Vibrio cholerae responds to environmental changes by altering the protein composition of its outer membrane. In rich medium, V. cholerae expresses almost exclusively the outer membrane porin OmpU, whereas in minimal medium, OmpT is the dominant porin. The supplementation of a minimal medium with a mixture of asparagine, arginine, glutamic acid, and serine (NRES) promotes OmpU production and OmpT repression at levels similar to those seen with rich media. Here we show that the altered Omp profile is not due to an increase in the growth rate in the presence of supplemental amino acids but requires the addition of specific amino acids. The effects of the NRES mix on Omp production were mediated by ToxR, a known regulator of omp gene expression. No changes in the Omp profile were detected in a toxR mutant. Supplementation with the NRES mix resulted in significantly higher levels of ToxR, and the elevated ToxR levels were sufficient to cause a switch in Omp synthesis. The increase in the level of the ToxR protein correlated with an increase in toxR mRNA levels and was observed only when toxR was expressed from its native promoter. ToxS, which is required for ToxR activity, was necessary for NRES-mediated omp gene regulation but not for the increase in ToxR levels. The growth of V. cholerae in the presence of bile acids also resulted in Omp switching, and this required ToxR. However, unlike the NRES mix, bile acids did not increase either ToxR protein or toxR mRNA levels, suggesting a different mechanism of omp gene regulation by bile than that by amino acids.
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Abstract
The transcription factor Fur regulates the expression of a number of genes in Vibrio cholerae in response to changes in the level of available iron. Fur usually acts as a repressor, but here we show that Fur positively regulates the expression of ompT, which encodes a major outer membrane porin. OmpT levels increased when the bacteria were grown in medium containing relatively high levels of iron, and this effect required Fur. The level of ompT mRNA also is increased in the presence of iron and Fur. The effect of iron on OmpT levels was independent of the known ompT regulators ToxR and Crp, and it did not require RyhB, which has been shown to be responsible for positive regulation by iron of some V. cholerae genes. Electrophoretic mobility shift assays showed that Fur binds upstream of the ompT transcription start site in a region overlapping known binding sites for ToxR and Crp. These data suggest that Fur and iron positively regulate ompT expression through the direct binding of Fur to the ompT promoter.
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Pagel M, Delcour AH. Effects of conjugated and unconjugated bile acids on the activity of theVibrio choleraeporin OmpT. Mol Membr Biol 2010; 28:69-78. [DOI: 10.3109/09687688.2010.519727] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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Polymer partitioning and ion selectivity suggest asymmetrical shape for the membrane pore formed by epsilon toxin. Biophys J 2010; 99:782-9. [PMID: 20682255 DOI: 10.1016/j.bpj.2010.05.014] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2010] [Revised: 04/27/2010] [Accepted: 05/03/2010] [Indexed: 12/25/2022] Open
Abstract
Using poly-(ethylene glycol)s of different molecular weights, we probe the channels formed in planar lipid bilayers by epsilon toxin secreted by the anaerobic bacterium Clostridium perfringens. We find that the pore is highly asymmetric. The cutoff size of polymers entering the pore through its opening from the cis side, the side of toxin addition, is approximately 500 Da, whereas the cutoff size for the polymers entering from the trans side is approximately 2300 Da. Comparing these characteristic molecular weights with those reported earlier for OmpF porin and the alpha-Hemolysin channel, we estimate the radii of cis and trans openings as 0.4 nm and 1.0 nm, respectively. The simplest geometry corresponding to these findings is that of a truncated cone. The asymmetry of the pore is also confirmed by measurements of the reversal potential at oppositely directed salt gradients. The moderate anionic selectivity of the channel is salted-out more efficiently when the salt concentration is higher at the trans side of the pore.
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