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Ortega-Sanz I, Bocigas C, Melero B, Rovira J. Phase variation modulates the multi-phenotypes displayed by clinical Campylobacter jejuni strains. Food Microbiol 2024; 117:104397. [PMID: 37918995 DOI: 10.1016/j.fm.2023.104397] [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: 02/14/2023] [Revised: 09/15/2023] [Accepted: 10/03/2023] [Indexed: 11/04/2023]
Abstract
The high incidence and prevalence of Campylobacter spp. in the food supply chain entail the importance to understand their mechanisms developed to withstand harsh environmental conditions encountered. Different stress conditions and phenotypic approaches were evaluated to study the behaviour of five clinical C. jejuni isolates with different genotypes, including the tolerance to oxygen and the oxidants hydrogen peroxide and cumene hydroperoxide, the motility and the ability to form biofilm on polystyrene and stainless steel at different temperatures and atmospheres. Whole Genome Sequencing was performed to analyse the occurrence of 216 genes involved in these mechanisms plus phase variation. The isolates showed high tolerance to oxygen and peroxide stress with different swimming motility performances and biofilm formation abilities. Aerotolerance was related with a reduced sensitive to peroxide stress and a loss of motility that promotes biofilm formation depending on the material surface. Comparative genomics did not reveal any clear gene pattern, although phase variation occurring during host infection was observed to be crucial for the modulation of the different survival mechanisms adopted by the bacteria. These findings reveal that the bacteria can combine diverse and complex strategies in an efficient manner to survive and persist in the environment.
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Affiliation(s)
- Irene Ortega-Sanz
- Department of Biotechnology and Food Science, University of Burgos, Burgos, Spain
| | - Carolina Bocigas
- Department of Biotechnology and Food Science, University of Burgos, Burgos, Spain
| | - Beatriz Melero
- Department of Biotechnology and Food Science, University of Burgos, Burgos, Spain
| | - Jordi Rovira
- Department of Biotechnology and Food Science, University of Burgos, Burgos, Spain.
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2
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Kanaan MHG. Effect of biofilm formation in a hostile oxidative stress environment on the survival of Campylobacter jejuni recovered from poultry in Iraqi markets. Vet World 2024; 17:136-142. [PMID: 38406363 PMCID: PMC10884572 DOI: 10.14202/vetworld.2024.136-142] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2023] [Accepted: 12/14/2023] [Indexed: 02/27/2024] Open
Abstract
Background and Aim Campylobacter jejuni is a major contributor to bacterial enteritis, a common health problem. The resistance of this microaerophilic bacterium to oxidative stress allows it to thrive under aerobic conditions. This study aimed to investigate whether the capacity of C. jejuni to form biofilms in the presence of oxidative stress contributes to the pathogen's ability to thrive in agricultural settings as well as in chicken slaughter lines. Materials and Methods Twenty identified strains originating from chicken samples (eight from caeca contents and 12 from frozen chicken carcasses) were previously isolated and identified according to standard bacteriological protocols, followed by confirmation at the species level using multiplex polymerase chain reaction assay. Crystal violet staining was used to evaluate biofilm formation by these bacteria. Two exposure periods to gaseous ozone (1 and 2 min) were used to assess resistance to oxidative damage. Results Most of the strong biofilm-forming Campylobacter strains came from imported frozen chicken meat (25%), whereas only 10% came from caeca content. After exposure to gaseous ozone at 600 mg/h for 2 min, strong biofilm-producing strains exhibited a higher survival rate with a limited reduction of up to 3 logs, whereas negative biofilm-producing strains exhibited a limited survival rate with a reduction of 6 logs. Conclusion Based on our findings, we hypothesized that the presence of C. jejuni strains capable of forming biofilms in poultry farms and/or chicken production facilities triggers a public health alarm as this bacterium seems to be able to adapt more easily to live and thrive in hostile environmental conditions.
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Affiliation(s)
- Manal H. G. Kanaan
- Department of Nursing, Technical Institute of Suwaria, Middle Technical University, Baghdad, Iraq
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3
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Ratti A, Fassi EMA, Forlani F, Zangrossi M, Mori M, Cappitelli F, Roda G, Villa S, Villa F, Grazioso G. Unlocking the Antibiofilm Potential of Natural Compounds by Targeting the NADH:quinone Oxidoreductase WrbA. Antioxidants (Basel) 2023; 12:1612. [PMID: 37627607 PMCID: PMC10451263 DOI: 10.3390/antiox12081612] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2023] [Revised: 07/31/2023] [Accepted: 08/12/2023] [Indexed: 08/27/2023] Open
Abstract
Biofilm-dwelling cells endure adverse conditions, including oxidative imbalances. The NADH:quinone oxidoreductase enzyme WrbA has a crucial role in the mechanism of action of antibiofilm molecules such as ellagic and salicylic acids. This study aimed to exploit the potential of the WrbA scaffold as a valuable target for identifying antibiofilm compounds at non-lethal concentrations. A three-dimensional computational model, based on the published WrbA structure, was used to screen natural compounds from a virtual library of 800,000 compounds. Fisetin, morin, purpurogallin, NZ028, and NZ034, along with the reference compound ellagic acid, were selected. The antibiofilm effect of the molecules was tested at non-lethal concentrations evaluating the cell-adhesion of wild-type and WrbA-deprived Escherichia coli strains through fluorochrome-based microplate assays. It was shown that, except for NZ028, all of the selected molecules exhibited notable antibiofilm effects. Purpurogallin and NZ034 showed excellent antibiofilm performances at the lowest concentration of 0.5 μM, in line with ellagic acid. The observed loss of activity and the level of reactive oxygen species in the mutant strain, along with the correlation with terms contributing to the ligand-binding free energy on WrbA, strongly indicates the WrbA-dependency of purpurogallin and NZ034. Overall, the molecular target WrbA was successfully employed to identify active compounds at non-lethal concentrations, thus revealing, for the first time, the antibiofilm efficacy of purpurogallin and NZ034.
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Affiliation(s)
- Alessandro Ratti
- Department of Pharmaceutical Sciences, University of Milan, Via L. Mangiagalli 25, 20133 Milan, Italy
| | - Enrico M A Fassi
- Department of Pharmaceutical Sciences, University of Milan, Via L. Mangiagalli 25, 20133 Milan, Italy
| | - Fabio Forlani
- Department of Food Environmental and Nutritional Science (DeFENS), University of Milan, Via Celoria 2, 20133 Milan, Italy
| | - Maurizio Zangrossi
- Department of Food Environmental and Nutritional Science (DeFENS), University of Milan, Via Celoria 2, 20133 Milan, Italy
| | - Matteo Mori
- Department of Pharmaceutical Sciences, University of Milan, Via L. Mangiagalli 25, 20133 Milan, Italy
| | - Francesca Cappitelli
- Department of Food Environmental and Nutritional Science (DeFENS), University of Milan, Via Celoria 2, 20133 Milan, Italy
| | - Gabriella Roda
- Department of Pharmaceutical Sciences, University of Milan, Via L. Mangiagalli 25, 20133 Milan, Italy
| | - Stefania Villa
- Department of Pharmaceutical Sciences, University of Milan, Via L. Mangiagalli 25, 20133 Milan, Italy
| | - Federica Villa
- Department of Food Environmental and Nutritional Science (DeFENS), University of Milan, Via Celoria 2, 20133 Milan, Italy
| | - Giovanni Grazioso
- Department of Pharmaceutical Sciences, University of Milan, Via L. Mangiagalli 25, 20133 Milan, Italy
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He J, Gao X, Huang H, Hao J. Proposal and Verification of the Theory of Layer-by-Layer Elimination of Biofilm in Listeria monocytogenes. Foods 2023; 12:foods12071361. [PMID: 37048183 PMCID: PMC10093742 DOI: 10.3390/foods12071361] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2023] [Accepted: 03/21/2023] [Indexed: 04/14/2023] Open
Abstract
Biofilms are microbial communities that represent a high abundance of microbial life forms on Earth. Within biofilms, structural changes during clearance processes occur in three spatial and temporal dimensions; therefore, microscopy and quantitative image analysis are essential in elucidating their function. Here, we present confocal laser scanning microscopy (CLSM) in conjunction with ISA-2 software analysis for the automated and high-throughput quantification, analysis, and visualisation of biofilm interiors and overall biofilm properties in three spatial and temporal dimensions. This paper discusses the removal process of Listeria monocytogenes (LM) biofilms using slightly acidic electrolytic water, non-electrolytic hypochlorite water, and alternating the use of strongly acidic and strongly alkaline electrolytic water. The results show that the biofilm gradually thins and gutters from the initial viscous dense and thick morphology under the action of either biocide. This process is consistent with first-level kinetics. After CLSM filming to observe the biofilm structure, analysis software was used to process and quantify the biovolume, average biofilm thickness, biofilm roughness and other indicators; fluorescence enzyme markers were used to verify the remaining amount of extracellular nucleic acid. In this study, we proposed and validated the theory of layer-by-layer elimination of LM biofilm.
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Affiliation(s)
- Jialin He
- College of Food Science and Biology, Hebei University of Science and Technology, No. 26 Yuxiang Street, Shijiazhuang 050018, China
| | - Xiangyu Gao
- College of Food Science and Biology, Hebei University of Science and Technology, No. 26 Yuxiang Street, Shijiazhuang 050018, China
| | - Hanbing Huang
- College of Food Science and Biology, Hebei University of Science and Technology, No. 26 Yuxiang Street, Shijiazhuang 050018, China
| | - Jianxiong Hao
- College of Food Science and Biology, Hebei University of Science and Technology, No. 26 Yuxiang Street, Shijiazhuang 050018, China
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5
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Kim J, Park M, Ahn E, Mao Q, Chen C, Ryu S, Jeon B. Stimulation of Surface Polysaccharide Production under Aerobic Conditions Confers Aerotolerance in Campylobacter jejuni. Microbiol Spectr 2023; 11:e0376122. [PMID: 36786626 PMCID: PMC10100837 DOI: 10.1128/spectrum.03761-22] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2022] [Accepted: 01/30/2023] [Indexed: 02/15/2023] Open
Abstract
The ability of a foodborne pathogen to tolerate environmental stress critically affects food safety by increasing the risk of pathogen survival and transmission in the food supply chain. Campylobacter jejuni, a leading bacterial cause of foodborne illnesses, is an obligate microaerophile and is sensitive to atmospheric levels of oxygen. Currently, the molecular mechanisms of how C. jejuni withstands oxygen toxicity under aerobic conditions have not yet been fully elucidated. Here, we show that when exposed to aerobic conditions, C. jejuni develops a thick layer of bacterial capsules, which in turn protect C. jejuni under aerobic conditions. The presence of both capsular polysaccharides and lipooligosaccharides is required to protect C. jejuni from excess oxygen in oxygen-rich environments by alleviating oxidative stress. Under aerobic conditions, C. jejuni undergoes substantial transcriptomic changes, particularly in the genes of carbon metabolisms involved in amino acid uptake, the tricarboxylic acid (TCA) cycle, and the Embden-Meyerhof-Parnas (EMP) pathway despite the inability of C. jejuni to grow aerobically. Moreover, the stimulation of carbon metabolism by aerobiosis increases the level of glucose-6-phosphate, the EMP pathway intermediate required for the synthesis of surface polysaccharides. The disruption of the TCA cycle eliminates aerobiosis-mediated stimulation of surface polysaccharide production and markedly compromises aerotolerance in C. jejuni. These results in this study provide novel insights into how an oxygen-sensitive microaerophilic pathogen survives in oxygen-rich environments by adapting its metabolism and physiology. IMPORTANCE Oxygen-sensitive foodborne pathogens must withstand oxygen toxicity in aerobic environments during transmission to humans. C. jejuni is a major cause of gastroenteritis, accounting for 400 million to 500 million infection cases worldwide per year. As an obligate microaerophile, C. jejuni is sensitive to air-level oxygen. However, it has not been fully explained how this oxygen-sensitive zoonotic pathogen survives in aerobic environments and is transmitted to humans. Here, we show that under aerobic conditions, C. jejuni boosts its carbon metabolism to produce a thick layer of bacterial capsules, which in turn act as a protective barrier conferring aerotolerance. The new findings in this study improve our understanding of how oxygen-sensitive C. jejuni can survive in aerobic environments.
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Affiliation(s)
- Jinshil Kim
- Department of Food and Animal Biotechnology, Research Institute of Agriculture and Life Sciences, Seoul National University, Seoul, Republic of Korea
- Department of Agricultural Biotechnology, Seoul National University, Seoul, Republic of Korea
- Center for Food and Bioconvergence, Seoul National University, Seoul, Republic of Korea
| | - Myungseo Park
- Division of Environmental Health Sciences, School of Public Health, University of Minnesota, Minneapolis, Minnesota, USA
| | - Eunbyeol Ahn
- Department of Food and Animal Biotechnology, Research Institute of Agriculture and Life Sciences, Seoul National University, Seoul, Republic of Korea
- Department of Agricultural Biotechnology, Seoul National University, Seoul, Republic of Korea
| | - Qingqing Mao
- Department of Food Science and Nutrition, University of Minnesota, Saint Paul, Minnesota, USA
| | - Chi Chen
- Department of Food Science and Nutrition, University of Minnesota, Saint Paul, Minnesota, USA
| | - Sangryeol Ryu
- Department of Food and Animal Biotechnology, Research Institute of Agriculture and Life Sciences, Seoul National University, Seoul, Republic of Korea
- Department of Agricultural Biotechnology, Seoul National University, Seoul, Republic of Korea
- Center for Food and Bioconvergence, Seoul National University, Seoul, Republic of Korea
| | - Byeonghwa Jeon
- Division of Environmental Health Sciences, School of Public Health, University of Minnesota, Minneapolis, Minnesota, USA
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Thakur P, Alaba MO, Rauniyar S, Singh RN, Saxena P, Bomgni A, Gnimpieba EZ, Lushbough C, Goh KM, Sani RK. Text-Mining to Identify Gene Sets Involved in Biocorrosion by Sulfate-Reducing Bacteria: A Semi-Automated Workflow. Microorganisms 2023; 11:119. [PMID: 36677411 PMCID: PMC9867429 DOI: 10.3390/microorganisms11010119] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2022] [Revised: 12/12/2022] [Accepted: 12/14/2022] [Indexed: 01/05/2023] Open
Abstract
A significant amount of literature is available on biocorrosion, which makes manual extraction of crucial information such as genes and proteins a laborious task. Despite the fast growth of biology related corrosion studies, there is a limited number of gene collections relating to the corrosion process (biocorrosion). Text mining offers a potential solution by automatically extracting the essential information from unstructured text. We present a text mining workflow that extracts biocorrosion associated genes/proteins in sulfate-reducing bacteria (SRB) from literature databases (e.g., PubMed and PMC). This semi-automatic workflow is built with the Named Entity Recognition (NER) method and Convolutional Neural Network (CNN) model. With PubMed and PMCID as inputs, the workflow identified 227 genes belonging to several Desulfovibrio species. To validate their functions, Gene Ontology (GO) enrichment and biological network analysis was performed using UniprotKB and STRING-DB, respectively. The GO analysis showed that metal ion binding, sulfur binding, and electron transport were among the principal molecular functions. Furthermore, the biological network analysis generated three interlinked clusters containing genes involved in metal ion binding, cellular respiration, and electron transfer, which suggests the involvement of the extracted gene set in biocorrosion. Finally, the dataset was validated through manual curation, yielding a similar set of genes as our workflow; among these, hysB and hydA, and sat and dsrB were identified as the metal ion binding and sulfur metabolism genes, respectively. The identified genes were mapped with the pangenome of 63 SRB genomes that yielded the distribution of these genes across 63 SRB based on the amino acid sequence similarity and were further categorized as core and accessory gene families. SRB's role in biocorrosion involves the transfer of electrons from the metal surface via a hydrogen medium to the sulfate reduction pathway. Therefore, genes encoding hydrogenases and cytochromes might be participating in removing hydrogen from the metals through electron transfer. Moreover, the production of corrosive sulfide from the sulfur metabolism indirectly contributes to the localized pitting of the metals. After the corroboration of text mining results with SRB biocorrosion mechanisms, we suggest that the text mining framework could be utilized for genes/proteins extraction and significantly reduce the manual curation time.
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Affiliation(s)
- Payal Thakur
- Department of Chemical and Biological Engineering, South Dakota School of Mines and Technology, Rapid City, SD 57701, USA
- Data Driven Material Discovery Center for Bioengineering Innovation, South Dakota School of Mines and Technology, Rapid City, SD 57701, USA
| | - Mathew O. Alaba
- Department of Biomedical Engineering, University of South Dakota, Sioux Falls, SD 57069, USA
| | - Shailabh Rauniyar
- Department of Chemical and Biological Engineering, South Dakota School of Mines and Technology, Rapid City, SD 57701, USA
- 2-Dimensional Materials for Biofilm Engineering, Science and Technology, South Dakota School of Mines and Technology, Rapid City, SD 57701, USA
| | - Ram Nageena Singh
- Department of Chemical and Biological Engineering, South Dakota School of Mines and Technology, Rapid City, SD 57701, USA
- 2-Dimensional Materials for Biofilm Engineering, Science and Technology, South Dakota School of Mines and Technology, Rapid City, SD 57701, USA
| | - Priya Saxena
- Department of Chemical and Biological Engineering, South Dakota School of Mines and Technology, Rapid City, SD 57701, USA
- Data Driven Material Discovery Center for Bioengineering Innovation, South Dakota School of Mines and Technology, Rapid City, SD 57701, USA
| | - Alain Bomgni
- Department of Biomedical Engineering, University of South Dakota, Sioux Falls, SD 57069, USA
| | - Etienne Z. Gnimpieba
- Data Driven Material Discovery Center for Bioengineering Innovation, South Dakota School of Mines and Technology, Rapid City, SD 57701, USA
- Department of Biomedical Engineering, University of South Dakota, Sioux Falls, SD 57069, USA
- 2-Dimensional Materials for Biofilm Engineering, Science and Technology, South Dakota School of Mines and Technology, Rapid City, SD 57701, USA
| | - Carol Lushbough
- Department of Biomedical Engineering, University of South Dakota, Sioux Falls, SD 57069, USA
| | - Kian Mau Goh
- Faculty of Science, Universiti Teknologi Malaysia, Skudai 81310, Johor, Malaysia
| | - Rajesh Kumar Sani
- Department of Chemical and Biological Engineering, South Dakota School of Mines and Technology, Rapid City, SD 57701, USA
- Data Driven Material Discovery Center for Bioengineering Innovation, South Dakota School of Mines and Technology, Rapid City, SD 57701, USA
- 2-Dimensional Materials for Biofilm Engineering, Science and Technology, South Dakota School of Mines and Technology, Rapid City, SD 57701, USA
- BuG ReMeDEE Consortium, South Dakota School of Mines and Technology, Rapid City, SD 57701, USA
- Composite and Nanocomposite Advanced Manufacturing Centre—Biomaterials, Rapid City, SD 57701, USA
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7
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Tarafdar A, Lim JY, Kwon JH. UV stabilizers can foster early development of biofilms on freshwater microplastics. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2022; 315:120444. [PMID: 36265727 DOI: 10.1016/j.envpol.2022.120444] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/07/2022] [Revised: 10/13/2022] [Accepted: 10/13/2022] [Indexed: 06/16/2023]
Abstract
Interactions between microbes and microplastics are important as of emerging plastic loads in the global environment. Although diverse plastic additives are used in large amounts, there are very few studies on a quantitative comparison of plastisphere on plastics with different plastic additives. We studied the effects of two widely used UV stabilizers (benzotriazole-type UV-327 and benzophenone-type UV-531 were selected based on their persistence and toxicity) in low-density polyethylene (LDPE) on freshwater microbes. This is the first study on the sole effects of UV stabilizers used as plastic additives on freshwater in situ plastisphere biofilm development. Confocal laser scanning microscopy, assisted with proper differentiating fluorochromes and threshold-based 3D segmentation of data, was used to visualize and quantify biofilm. On the first week of biofilm growth, there was very little biovolume and a negligible amount of phototrophs on pristine LDPE contrasting other substrates. Biovolumes were significantly higher on LDPE with UV stabilizers (up to 159% higher than pristine LDPE), although the biomass was mostly dead due to toxicity (>100% higher dead biovolume than live biovolume in LDPE with UV stabilizers). After the fourth week, marginally higher biovolumes along with a revival of the biomass on LDPE with UV stabilizers were observed. The ability to induce microorganismic intracellular reactive oxygen species by UV stabilizers was detected, which may stimulate biofilm growth during the primary phase of biofilm development. Atomic force microscopy analysis denoted that LDPE with UV stabilizers exhibit considerably stronger adhesion force than pristine LDPE. These observations suggest that UV stabilizers can foster the early attachment of microbes to microplastics while killing the surface contacting layer. An alive upper layer of microbes can get developed on the dead biofilm without much disruption due to the toxicity of UV stabilizers. This occurrence can eventually boost the early development of biofilms on plastics.
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Affiliation(s)
- Abhrajyoti Tarafdar
- Division of Environmental Science and Ecological Engineering, Korea University, Seoul, 02841, Republic of Korea.
| | - Ja-Yun Lim
- Department of Clinical Laboratory Science, Hyejeon College, 19 Daehak-1gil, Hongsung-eup, Hongsung-gun, Chungnam, 32244, Republic of Korea.
| | - Jung-Hwan Kwon
- Division of Environmental Science and Ecological Engineering, Korea University, Seoul, 02841, Republic of Korea.
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Nennig M, Clément A, Longueval E, Bernardi T, Ragimbeau C, Tresse O. Metaphenotypes associated with recurrent genomic lineages of Campylobacter jejuni responsible for human infections in Luxembourg. Front Microbiol 2022; 13:901192. [PMID: 36160185 PMCID: PMC9490421 DOI: 10.3389/fmicb.2022.901192] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2022] [Accepted: 08/01/2022] [Indexed: 11/13/2022] Open
Abstract
Campylobacter jejuni is a leading cause of foodborne illnesses worldwide. Although considered fragile, this microaerophilic bacterium is able to survive in various challenging environments, which subsequently constitutes multiple sources of transmission for human infection. To test the assumption of acquiring specific features for adaptation and survival, we established a workflow of phenotypic tests related to the survival and the persistence of recurrent and sporadic strains. A representative collection of 83 strains isolated over 13 years from human, mammal, poultry, and environmental sources in Luxembourg, representing different spreading patterns (endemic, epidemic, and sporadic), was screened for survival to oxidative stresses, for acclimating to aerobic conditions (AC), and for persistence on abiotic surfaces. Using the cgMLST Oxford typing scheme for WGS data, the collection was classified into genomic lineages corresponding to host-generalist strains (lineages A and D, CC ST-21), host-specific strains (lineage B, CC ST-257 and lineage C, CC ST-464) and sporadic strains. We established that when a strain survives concentrations beyond 0.25 mM superoxide stress, it is six times more likely to survive hyperoxide stress and that a highly adherent strain is 14 times more likely to develop a biofilm. Surprisingly, more than half of the strains could acclimate to AC but this capacity does not explain the difference between recurrent genomic lineages and sporadic strains and the survival to oxidative stresses, while recurrent strains have a significantly higher adhesion/biofilm formation capacity than sporadic ones. From this work, the genomic lineages with more stable genomes could be characterized by a specific combination of phenotypes, called metaphenotypes. From the functional genomic analyses, the presence of a potentially functional T6SS in the strains of lineage D might explain the propensity of these strains to be strong biofilm producers. Our findings support the hypothesis that phenotypical abilities contribute to the spatio-temporal adaptation and survival of stable genomic lineages. It suggests a selection of better-adapted and persistent strains in challenging stress environments, which could explain the prevalence of these lineages in human infections.
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Affiliation(s)
- Morgane Nennig
- Epidemiology and Microbial Genomics, Laboratoire National de Santé, Dudelange, Luxembourg
- UMR-1280 PhAN, INRAE, Nantes, France
| | - Arnaud Clément
- BioFilm Control, Biopôle Clermont-Limagne, Saint-Beauzire, France
| | - Emmanuelle Longueval
- Epidemiology and Microbial Genomics, Laboratoire National de Santé, Dudelange, Luxembourg
| | - Thierry Bernardi
- BioFilm Control, Biopôle Clermont-Limagne, Saint-Beauzire, France
| | - Catherine Ragimbeau
- Epidemiology and Microbial Genomics, Laboratoire National de Santé, Dudelange, Luxembourg
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Giaouris E. Relevance and Importance of Biofilms in the Resistance and Spreading of Campylobacter spp. Within the Food Chain. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2022. [DOI: 10.1007/5584_2022_749] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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10
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Ohadi E, Bakhshi B, Kalani BS, Talebi M, Irajian G. Transcriptome analysis of biofilm formation under aerobic and microaerobic conditions in clinical isolates of Campylobacter spp. Res Vet Sci 2021; 142:24-30. [PMID: 34847463 DOI: 10.1016/j.rvsc.2021.11.009] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2020] [Revised: 07/29/2021] [Accepted: 11/16/2021] [Indexed: 01/16/2023]
Abstract
It has been well documented that Campylobacter is the leading cause of foodborne infections and bacterial enteritis in high-income countries. The gastrointestinal tract of most warm-blooded animals, such as mammals and poultry, is prone to this pathogen. Infections caused by this bacterium in humans have usually been associated with the consumption of contaminated poultry meat. The important point about Campylobacter is that this bacterium has adapted to harsh environmental conditions along the food chain (poultry digestive tract to the consumer's plate) and developed an adapted mechanism to those conditions. This study aimed to compare the ability of Campylobacter jejuni and Campylobacter coli strains to form biofilms under aerobic and microaerobic conditions. The presence and expression of flab, FliS, DnaK, luxs, CsrA, Cj0688, and cosR genes involved in biofilm formation were investigated. Finally, the correlation between the biofilm forming ability of Campylobacter isolates and the presence/expression of selected genes has been explored. A significant correlation was observed between the presence and expression of some genes and the degree of biofilm formation in C. jejuni and C. coli isolates. A strong biofilm production was detected in strains harboring all selected genes with greater expression levels. The ability of C. jejuni and C. coli strains in biofilm formation is associated with the coordinated function and convergent expression of the selected genes. Seemingly, stress response- and motility-related genes have the most involvement in biofilm formation of C. jejuni and C. coli strains, while other genes have an accessory role in this phenomenon.
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Affiliation(s)
- Elnaz Ohadi
- Department of Microbiology, Faculty of Medicine, Iran University of Medical Sciences, Tehran, Iran; Microbial Biotechnology Research Center, Iran University of Medical Sciences, Tehran, Iran
| | - Bita Bakhshi
- Department of Bacteriology, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran.
| | - Behrooz Sadeghi Kalani
- Department of Medical Microbiology, Faculty of Medicine, Ilam University of Medical Sciences, Ilam, Iran; Clinical Microbiology Research Center, Ilam University of Medical Sciences, Ilam, Iran
| | - Malihe Talebi
- Department of Microbiology, Faculty of Medicine, Iran University of Medical Sciences, Tehran, Iran; Microbial Biotechnology Research Center, Iran University of Medical Sciences, Tehran, Iran
| | - Gholamreza Irajian
- Department of Microbiology, Faculty of Medicine, Iran University of Medical Sciences, Tehran, Iran; Microbial Biotechnology Research Center, Iran University of Medical Sciences, Tehran, Iran.
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11
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In vitro virulence potential, surface attachment and transcriptional response of sublethally injured Listeria monocytogenes following exposure to peracetic acid. Appl Environ Microbiol 2021; 88:e0158221. [PMID: 34731051 DOI: 10.1128/aem.01582-21] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The disinfectant Peracetic acid (PAA) can cause high levels of sublethal injury to L. monocytogenes. This study aims to evaluate phenotypic and transcriptional characteristics concerning surface attachment and virulence potential of sublethally injured L. monocytogenes ScottA and EGDe after exposure to 0.75 ppm PAA for 90 min at 4°C and subsequent incubation in TSBY at 4°C. Results showed that injured L. monocytogenes cells (99% of total population) were able to attach (after 2 and 24h) on stainless steel coupons at 4°C and 20°C. In vitro virulence assays using human intestinal epithelial Caco-2 cells showed that injured L. monocytogenes could invade host cells but could not proliferate intracellularly. In vitro virulence response was strain-dependent; injured ScottA was more invasive than EGDe. Assessment of PAA-injury at the transcriptional level showed upregulation of genes (motB, flaA) involved in flagellum motility and surface attachment. The transcriptional response of L. monocytogenes EGDe and ScottA was different; only injured ScottA demonstrated upregulation of the virulence genes inlA and plcA. Downregulation of the stress-related genes fri and kat, and upregulation of lmo0669 was observed in injured ScottA. The obtained results indicate that sublethally-injured L. monocytogenes cells may retain part of their virulence properties as well as their ability to adhere on food processing surfaces. Transmission to food products and introduction of these cells in the food chain is therefore a plausible scenario that is worth taking into consideration in terms of risk assessment. Importance L. monocytogenes is the causative agent of listeriosis a serious food-borne illness. Antimicrobial practices, such as disinfectants used for the elimination of this pathogen in food industry can produce a sublethally injured population fraction. Injured cells of this pathogen, that may survive an antimicrobial treatment, may pose a food safety-risk. Nevertheless, knowledge regarding how sublethal injury may impact important cellular traits and phenotypic responses of this pathogen is limited. This work suggests that sublethally injured L. monocytogenes cells maintain the virulence and surface attachment potential and highlights the importance of the occurrence of sublethally injured cells regarding food safety.
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Liu Z, Li L, Fang Z, Lee Y, Zhao J, Zhang H, Chen W, Li H, Lu W. Integration of Transcriptome and Metabolome Reveals the Genes and Metabolites Involved in Bifidobacterium bifidum Biofilm Formation. Int J Mol Sci 2021; 22:ijms22147596. [PMID: 34299216 PMCID: PMC8304991 DOI: 10.3390/ijms22147596] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2021] [Revised: 07/11/2021] [Accepted: 07/12/2021] [Indexed: 01/14/2023] Open
Abstract
Bifidobacterium bifidum strains, an important component of probiotic foods, can form biofilms on abiotic surfaces, leading to increased self-resistance. However, little is known about the molecular mechanism of B. bifidum biofilm formation. A time series transcriptome sequencing and untargeted metabolomics analysis of both B. bifidum biofilm and planktonic cells was performed to identify key genes and metabolites involved in biofilm formation. Two hundred thirty-five nonredundant differentially expressed genes (DEGs) (including vanY, pstS, degP, groS, infC, groL, yajC, tadB and sigA) and 219 nonredundant differentially expressed metabolites (including L-threonine, L-cystine, L-tyrosine, ascorbic acid, niacinamide, butyric acid and sphinganine) were identified. Thirteen pathways were identified during the integration of both transcriptomics and metabolomics data, including ABC transporters; quorum sensing; two-component system; oxidative phosphorylation; cysteine and methionine metabolism; glutathione metabolism; glycine, serine and threonine metabolism; and valine, leucine and isoleucine biosynthesis. The DEGs that relate to the integration pathways included asd, atpB, degP, folC, ilvE, metC, pheA, pstS, pyrE, serB, ulaE, yajC and zwf. The differentially accumulated metabolites included L-cystine, L-serine, L-threonine, L-tyrosine, methylmalonate, monodehydroascorbate, nicotinamide, orthophosphate, spermine and tocopherol. These results indicate that quorum sensing, two-component system and amino acid metabolism are essential during B. bifidum biofilm formation.
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Affiliation(s)
- Zongmin Liu
- State Key Laboratory of Food Science and Technology, Jiangnan University, Wuxi 214122, China; (Z.L.); (L.L.); (Z.F.); (J.Z.); (H.Z.); (W.C.); (H.L.)
- School of Food Science and Technology, Jiangnan University, Wuxi 214122, China
| | - Lingzhi Li
- State Key Laboratory of Food Science and Technology, Jiangnan University, Wuxi 214122, China; (Z.L.); (L.L.); (Z.F.); (J.Z.); (H.Z.); (W.C.); (H.L.)
- School of Food Science and Technology, Jiangnan University, Wuxi 214122, China
| | - Zhifeng Fang
- State Key Laboratory of Food Science and Technology, Jiangnan University, Wuxi 214122, China; (Z.L.); (L.L.); (Z.F.); (J.Z.); (H.Z.); (W.C.); (H.L.)
- School of Food Science and Technology, Jiangnan University, Wuxi 214122, China
| | - Yuankun Lee
- Department of Microbiology & Immunology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 117545, Singapore;
- International Joint Research Laboratory for Pharmabiotics & Antibiotic Resistance, Jiangnan University, Wuxi 214122, China
| | - Jianxin Zhao
- State Key Laboratory of Food Science and Technology, Jiangnan University, Wuxi 214122, China; (Z.L.); (L.L.); (Z.F.); (J.Z.); (H.Z.); (W.C.); (H.L.)
- School of Food Science and Technology, Jiangnan University, Wuxi 214122, China
- National Engineering Research Center for Functional Food, Jiangnan University, Wuxi 214122, China
| | - Hao Zhang
- State Key Laboratory of Food Science and Technology, Jiangnan University, Wuxi 214122, China; (Z.L.); (L.L.); (Z.F.); (J.Z.); (H.Z.); (W.C.); (H.L.)
- School of Food Science and Technology, Jiangnan University, Wuxi 214122, China
- National Engineering Research Center for Functional Food, Jiangnan University, Wuxi 214122, China
| | - Wei Chen
- State Key Laboratory of Food Science and Technology, Jiangnan University, Wuxi 214122, China; (Z.L.); (L.L.); (Z.F.); (J.Z.); (H.Z.); (W.C.); (H.L.)
- School of Food Science and Technology, Jiangnan University, Wuxi 214122, China
- National Engineering Research Center for Functional Food, Jiangnan University, Wuxi 214122, China
| | - Haitao Li
- State Key Laboratory of Food Science and Technology, Jiangnan University, Wuxi 214122, China; (Z.L.); (L.L.); (Z.F.); (J.Z.); (H.Z.); (W.C.); (H.L.)
- School of Food Science and Technology, Jiangnan University, Wuxi 214122, China
| | - Wenwei Lu
- State Key Laboratory of Food Science and Technology, Jiangnan University, Wuxi 214122, China; (Z.L.); (L.L.); (Z.F.); (J.Z.); (H.Z.); (W.C.); (H.L.)
- School of Food Science and Technology, Jiangnan University, Wuxi 214122, China
- International Joint Research Laboratory for Pharmabiotics & Antibiotic Resistance, Jiangnan University, Wuxi 214122, China
- National Engineering Research Center for Functional Food, Jiangnan University, Wuxi 214122, China
- Correspondence: ; Tel.: +86-510-85197302
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Molecular Mechanisms of Campylobacter Biofilm Formation and Quorum Sensing. Curr Top Microbiol Immunol 2021. [PMID: 33620656 DOI: 10.1007/978-3-030-65481-8_11] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/08/2023]
Abstract
Even though Campylobacter spp. are known to be fastidious organisms, they can survive within the natural environment. One mechanism to withstand unfavourable conditions is the formation of biofilms, a multicellular structure composed of different bacterial and other microbial species which are embedded in an extracellular matrix. High oxygen levels, low substrate concentrations and the presence of external DNA stimulate the biofilm formation by C. jejuni. These external factors trigger internal adaptation processes, e.g. via regulating the expression of genes encoding proteins required for surface structure formation, as well as motility, stress response and antimicrobial resistance. Known genes impacting biofilm formation will be summarized in this review. The formation of biofilms as well as the expression of virulence genes is often regulated in a cell density depending manner by quorum sensing, which is mediated via small signalling molecules termed autoinducers. Even though quorum sensing mechanisms of other bacteria are well understood, knowledge on the role of these mechanisms in C. jejuni biofilm formation is still scarce. The LuxS enzyme involved in generation of autoinducer-2 is present in C. jejuni, but autoinducer receptors have not been identified so far. Phenotypes of C. jejuni strains lacking a functional luxS like reduced growth, motility, oxygen stress tolerance, biofilm formation, adhesion, invasion and colonization are also summarized within this chapter. However, these phenotypes are highly variable in distinct C. jejuni strains and depend on the culture conditions applied.
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Transcriptome Analysis Reveals the Genes Involved in Bifidobacterium Longum FGSZY16M3 Biofilm Formation. Microorganisms 2021; 9:microorganisms9020385. [PMID: 33672820 PMCID: PMC7917626 DOI: 10.3390/microorganisms9020385] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2021] [Revised: 01/29/2021] [Accepted: 02/08/2021] [Indexed: 12/11/2022] Open
Abstract
Biofilm formation has evolved as an adaptive strategy for bacteria to cope with harsh environmental conditions. Currently, little is known about the molecular mechanisms of biofilm formation in bifidobacteria. A time series transcriptome sequencing analysis of both biofilm and planktonic cells of Bifidobacterium longum FGSZY16M3 was performed to identify candidate genes involved in biofilm formation. Protein–protein interaction network analysis of 1296 differentially expressed genes during biofilm formation yielded 15 clusters of highly interconnected nodes, indicating that genes related to the SOS response (dnaK, groS, guaB, ruvA, recA, radA, recN, recF, pstA, and sufD) associated with the early stage of biofilm formation. Genes involved in extracellular polymeric substances were upregulated (epsH, epsK, efp, frr, pheT, rfbA, rfbJ, rfbP, rpmF, secY and yidC) in the stage of biofilm maturation. To further investigate the genes related to biofilm formation, weighted gene co-expression network analysis (WGCNA) was performed with 2032 transcript genes, leading to the identification of nine WGCNA modules and 133 genes associated with response to stress, regulation of gene expression, quorum sensing, and two-component system. These results indicate that biofilm formation in B. longum is a multifactorial process, involving stress response, structural development, and regulatory processes.
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Nennig M, Llarena AK, Herold M, Mossong J, Penny C, Losch S, Tresse O, Ragimbeau C. Investigating Major Recurring Campylobacter jejuni Lineages in Luxembourg Using Four Core or Whole Genome Sequencing Typing Schemes. Front Cell Infect Microbiol 2021; 10:608020. [PMID: 33489938 PMCID: PMC7819963 DOI: 10.3389/fcimb.2020.608020] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2020] [Accepted: 11/23/2020] [Indexed: 12/31/2022] Open
Abstract
Campylobacter jejuni is the leading cause of bacterial gastroenteritis, which has motivated the monitoring of genetic profiles circulating in Luxembourg since 13 years. From our integrated surveillance using a genotyping strategy based on an extended MLST scheme including gyrA and porA markers, an unexpected endemic pattern was discovered in the temporal distribution of genotypes. We aimed to test the hypothesis of stable lineages occurrence by implementing whole genome sequencing (WGS) associated with comprehensive and internationally validated schemes. This pilot study assessed four WGS-based typing schemes to classify a panel of 108 strains previously identified as recurrent or sporadic profiles using this in-house typing system. The strain collection included four common lineages in human infection (N = 67) initially identified from recurrent combination of ST-gyrA-porA alleles also detected in non-human samples: veterinary (N = 19), food (N = 20), and environmental (N = 2) sources. An additional set of 19 strains belonging to sporadic profiles completed the tested panel. All the strains were processed by WGS by using Illumina technologies and by applying stringent criteria for filtering sequencing data; we ensure robustness in our genomic comparison. Four typing schemes were applied to classify the strains: (i) the cgMLST SeqSphere+ scheme of 637 loci, (ii) the cgMLST Oxford scheme of 1,343 loci, (iii) the cgMLST INNUENDO scheme of 678 loci, and (iv) the wgMLST INNUENDO scheme of 2,795 loci. A high concordance between the typing schemes was determined by comparing the calculated adjusted Wallace coefficients. After quality control and analyses with these four typing schemes, 60 strains were confirmed as members of the four recurrent lineages regardless of the method used (N = 32, 12, 7, and 9, respectively). Our results indicate that, regardless of the typing scheme used, epidemic or endemic signals were detected as reflected by lineage B (ST2254-gyrA9-porA1) in 2014 or lineage A (ST19-gyrA8-porA7), respectively. These findings support the clonal expansion of stable genomes in Campylobacter population exhibiting a multi-host profile and accounting for the majority of clinical strains isolated over a decade. Such recurring genotypes suggest persistence in reservoirs, sources or environment, emphasizing the need to investigate their survival strategy in greater depth.
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Affiliation(s)
- Morgane Nennig
- Epidemiology and Microbial Genomics, Laboratoire National de Santé, Dudelange, Luxembourg.,INRAE, Oniris, SECALIM, Nantes, France
| | - Ann-Katrin Llarena
- Faculty of Veterinary Medicine, Norwegian University of Life Sciences, Oslo, Norway
| | - Malte Herold
- Epidemiology and Microbial Genomics, Laboratoire National de Santé, Dudelange, Luxembourg
| | - Joël Mossong
- Epidemiology and Microbial Genomics, Laboratoire National de Santé, Dudelange, Luxembourg
| | - Christian Penny
- Luxembourg Institute of Science and Technology, Environmental Research and Innovation Department, Belvaux, Luxembourg
| | - Serge Losch
- Laboratoire de Médecine Vétérinaire de l'Etat, Veterinary Services Administration, Dudelange, Luxembourg
| | | | - Catherine Ragimbeau
- Epidemiology and Microbial Genomics, Laboratoire National de Santé, Dudelange, Luxembourg
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Whelan MVX, Simpson JC, Ó Cróinín T. A novel high-content screening approach for the elucidation of C. jejuni biofilm composition and integrity. BMC Microbiol 2021; 21:2. [PMID: 33397288 PMCID: PMC7784365 DOI: 10.1186/s12866-020-02062-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2020] [Accepted: 11/23/2020] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Campylobacter jejuni is the leading cause of bacterial gastroenteritis worldwide and the main source of infection is contaminated chicken meat. Although this important human pathogen is an obligate microaerophile, it must survive atmospheric oxygen conditions to allow transmission from contaminated chicken meat to humans. It is becoming increasingly evident that formation of biofilm plays a key role in the survival of this organism for extended periods on poultry products. We have recently demonstrated a novel inducible model for the study of adherent C. jejuni biofilm formation under aerobic conditions. By taking advantage of supercoiling mediated gene regulation, incubation of C. jejuni with subinhibitory concentrations of the Gyrase B inhibitor novobiocin was shown to promote the consistent formation of metabolically active adherent biofilm. RESULTS In this study, we implement this model in conjunction with the fluorescent markers: TAMRA (live cells) and SytoX (dead cells, eDNA) to develop a novel systematic high-content imaging approach and describe how it can be implemented to gain quantifiable information about the integrity and extracellular polymeric substance (EPS) composition of adherent C. jejuni biofilm in aerobic conditions. We show that this produces a model with a consistent, homogenous biofilm that can be induced and used to screen a range of inhibitors of biofilm adherence and matrix formation. CONCLUSIONS This model allows for the first time a high throughput analysis of C. jejuni biofilms which will be invaluable in enabling researchers to develop mechanisms to disrupt these biofilms and reduce the viability of these bacteria under aerobic conditions.
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Affiliation(s)
- Matthew V X Whelan
- School of Biomolecular and Biomedical Science, University College Dublin, Belfield, Dublin 4, Ireland
| | - Jeremy C Simpson
- School of Biology and Environmental Science, University College Dublin, Belfield, Dublin 4, Ireland
| | - Tadhg Ó Cróinín
- School of Biomolecular and Biomedical Science, University College Dublin, Belfield, Dublin 4, Ireland.
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Shagieva E, Teren M, Michova H, Strakova N, Karpiskova R, Demnerova K. Adhesion, Biofilm Formation, and luxS Sequencing of Campylobacter jejuni Isolated From Water in the Czech Republic. Front Cell Infect Microbiol 2020; 10:596613. [PMID: 33330139 PMCID: PMC7718015 DOI: 10.3389/fcimb.2020.596613] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2020] [Accepted: 10/20/2020] [Indexed: 01/06/2023] Open
Abstract
The microaerophilic pathogen Campylobacter jejuni is a leading bacterial cause of human gastroenteritis in developed countries. Even though it has a reputation as a fastidious organism, C. jejuni is widespread and can be easily isolated from various animals, food, and environmental sources. It is suggested that an ability to form biofilms is probably necessary for the survival of C. jejuni under harsh environmental conditions. The first step required for successful biofilm formation is adhesion to a suitable surface. Therefore, in this work, the degree of adhesion was evaluated, followed by characterization and quantification of biofilms using confocal laser scanning microscopy (CLSM). A total of 15 isolates of C. jejuni were used in the experiments (12 isolates from surface and waste waters, 1 human clinical, 1 food and 1 ACTT BAA-2151 collection strain, all samples originated from the Czech Republic). Regardless of the sample origin, all C. jejuni isolates were able to adhere to the polystyrene surface within 30 min, with the number of attached cells increasing with the time of incubation. The resulting data showed that all isolates were able to form complex voluminous biofilms after 24 h of cultivation. The average amount of biovolume ranged from 3.59 × 106 µm3 to 17.50 × 106 µm3 in isolates obtained from different sources of water, 16.79 × 106 µm3 in the food isolate and 10.92 × 106 µm3 in the collection strain. However, the highest amount of biomass was produced by the human clinical isolate (25.48 × 106 µm3). Similar to the quantity, the architecture of the biofilms also differed, from a rugged flat monolayer of cells to large clustered structures. Further, all isolates were tested for the presence of the luxS gene, as the luxS/AI-2 (autoinducer-2) quorum sensing pathway has been previously connected with enhanced biofilm formation. Two isolates originated from surface waters did not possess the luxS gene. These isolates formed thinner and sparser biofilms lacking the presence of significant clusters. However, the ability to adhere to the surface was preserved. The sequencing of the luxS-containing fragments shown a high similarity of the luxS gene among the isolates.
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Affiliation(s)
- Ekaterina Shagieva
- Laboratory of Food Microbiology, Department of Biochemistry and Microbiology, University of Chemistry and Technology, Prague, Czechia
| | - Martin Teren
- Laboratory of Food Microbiology, Department of Biochemistry and Microbiology, University of Chemistry and Technology, Prague, Czechia
| | - Hana Michova
- Laboratory of Food Microbiology, Department of Biochemistry and Microbiology, University of Chemistry and Technology, Prague, Czechia
| | - Nicol Strakova
- Laboratory of Zoonoses and Antibiotic Resistance, Department of Microbiology and Antimicrobial Resistance, Veterinary Research Institute, Brno, Czechia
| | - Renata Karpiskova
- Laboratory of Zoonoses and Antibiotic Resistance, Department of Microbiology and Antimicrobial Resistance, Veterinary Research Institute, Brno, Czechia
| | - Katerina Demnerova
- Laboratory of Food Microbiology, Department of Biochemistry and Microbiology, University of Chemistry and Technology, Prague, Czechia
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Role of Superoxide Reductase FA796 in Oxidative Stress Resistance in Filifactor alocis. Sci Rep 2020; 10:9178. [PMID: 32513978 PMCID: PMC7280497 DOI: 10.1038/s41598-020-65806-3] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2020] [Accepted: 05/07/2020] [Indexed: 12/20/2022] Open
Abstract
Filifactor alocis, a Gram-positive anaerobic bacterium, is now a proposed diagnostic indicator of periodontal disease. Because the stress response of this bacterium to the oxidative environment of the periodontal pocket may impact its pathogenicity, an understanding of its oxidative stress resistance strategy is vital. Interrogation of the F. alocis genome identified the HMPREF0389_00796 gene that encodes for a putative superoxide reductase (SOR) enzyme. SORs are non-heme, iron-containing enzymes that can catalyze the reduction of superoxide radicals to hydrogen peroxide and are important in the protection against oxidative stress. In this study, we have functionally characterized the putative SOR (FA796) from F. alocis ATCC 35896. The recombinant FA796 protein, which is predicted to be a homotetramer of the 1Fe-SOR class, can reduce superoxide radicals. F. alocis FLL141 (∆FA796::ermF) was significantly more sensitive to oxygen/air exposure compared to the parent strain. Sensitivity correlated with the level of intracellular superoxide radicals. Additionally, the FA796-defective mutant had increased sensitivity to hydrogen peroxide-induced stress, was inhibited in its ability to form biofilm and had reduced survival in epithelial cells. Collectively, these results suggest that the F. alocis SOR protein is a key enzymatic scavenger of superoxide radicals and protects the bacterium from oxidative stress conditions.
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Mukhopadhyay R, Chacón KN, Jarvis JM, Talipov MR, Yukl ET. Structural insights into the mechanism of oxidative activation of heme-free H-NOX from Vibrio cholerae. Biochem J 2020; 477:1123-1136. [PMID: 32141496 PMCID: PMC7108781 DOI: 10.1042/bcj20200124] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2020] [Revised: 03/03/2020] [Accepted: 03/06/2020] [Indexed: 02/07/2023]
Abstract
Bacterial heme nitric oxide/oxygen (H-NOX) domains are nitric oxide (NO) or oxygen sensors. This activity is mediated through binding of the ligand to a heme cofactor. However, H-NOX from Vibrio cholerae (Vc H-NOX) can be easily purified in a heme-free state that is capable of reversibly responding to oxidation, suggesting a heme-independent function as a redox sensor. This occurs by oxidation of Cys residues at a zinc-binding site conserved in a subset of H-NOX homologs. Remarkably, zinc is not lost from the protein upon oxidation, although its ligation environment is significantly altered. Using a combination of computational and experimental approaches, we have characterized localized structural changes that accompany the formation of specific disulfide bonds between Cys residues upon oxidation. Furthermore, the larger-scale structural changes accompanying oxidation appear to mimic those changes observed upon NO binding to the heme-bound form. Thus, Vc H-NOX and its homologs may act as both redox and NO sensors by completely separate mechanisms.
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Affiliation(s)
- Roma Mukhopadhyay
- Department of Chemistry and Biochemistry, New Mexico State University, Las Cruces, NM 88003, U.S.A
| | - Kelly N. Chacón
- Department of Chemistry, Reed College, Portland, OR 97202, U.S.A
| | - Jacqueline M. Jarvis
- Department of Plant and Environmental Sciences, New Mexico State University, Las Cruces, NM 88003, U.S.A
| | - Marat R. Talipov
- Department of Chemistry and Biochemistry, New Mexico State University, Las Cruces, NM 88003, U.S.A
| | - Erik T. Yukl
- Department of Chemistry and Biochemistry, New Mexico State University, Las Cruces, NM 88003, U.S.A
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Chen J, Wang Y. Genetic determinants of Salmonella enterica critical for attachment and biofilm formation. Int J Food Microbiol 2020; 320:108524. [PMID: 32000116 DOI: 10.1016/j.ijfoodmicro.2020.108524] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2019] [Revised: 01/17/2020] [Accepted: 01/20/2020] [Indexed: 12/21/2022]
Abstract
Salmonella is a bacterial pathogen frequently involved in human gastrointestinal infections including those associated with low-moisture foods such as dehydrated food powders/spices, vegetable seeds, and tree nuts. The survival/persistence of Salmonella on low moisture foods and in dry environments is enhanced by its ability in developing biofilms. This study was undertaken to identify the genetic determinants critical for Salmonella attachment and biofilm formation. E. coli SM10 lambda pir, with a kanamycin resistant marker on mini-Tn10 (mini-Tn10:lacZ:kanr), an ampicillin resistant marker on the mini-Tn10-bearing suicidal plasmid pLBT and a streptomycin sensitive marker on the SM10 chromosome, was used as a donor (ampr, kanr, streps), and three Salmonella strains (amps, kans, strepr) were used as recipients in a transposon mutagenesis study. The donor and each recipient were co-incubated overnight on tryptic soy agar at 37 °C, and mutant colonies (amps, kanr, strepr) were subsequently selected. A single-banded degenerate PCR product, amplified from each mutant genome using oligonucleotide primers derived from the end of min-Tn10 and restriction enzyme EcoR I- or Pst I-recognizing sequence, were analyzed using the Sanger sequencing technology. Acquired DNA sequences were compared to those deposited in the Genbank using BLAST search. Cells of Salmonella mutants accumulated either significantly more or less (P < 0.05) biofilms than their parent cells on polystyrene surface. Sequence analysis of degenerate PCR products revealed that the mini-Tn10 from pLBT had inserted into the cdg, trx, fadI or rxt on Salmonella chromosomes. Results of the research will likely help strategize future antimicrobial intervention for control of pathogen attachment and biofilm formation.
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Affiliation(s)
- Jinru Chen
- Department of Food Science and Technology, The University of Georgia, 1109 Experiment St., Griffin, GA 30223-1797, USA.
| | - Yin Wang
- Department of Food Science and Technology, The University of Georgia, 1109 Experiment St., Griffin, GA 30223-1797, USA
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Whelan MVX, Ardill L, Koide K, Nakajima C, Suzuki Y, Simpson JC, Ó Cróinín T. Acquisition of fluoroquinolone resistance leads to increased biofilm formation and pathogenicity in Campylobacter jejuni. Sci Rep 2019; 9:18216. [PMID: 31796849 PMCID: PMC6890674 DOI: 10.1038/s41598-019-54620-1] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2019] [Accepted: 10/23/2019] [Indexed: 12/14/2022] Open
Abstract
The World Health Organization has listed C. jejuni as one of 12 microorganisms on a global priority list for antibiotic resistance due to a rapid increase in strains resistant to fluoroquinolone antibiotics. This fluoroquinolone resistance is conferred through a single point mutation in the QRDR region within the gyrA gene known to be involved in DNA supercoiling. We have previously revealed that changes in DNA supercoilikng play a major role in the regulation of virulence in C. jejuni with relaxation of DNA supercoiling associated with increased attachment to and invasion of human epithelial cells. The aim of this study was to investigate whether fluoroquinolone resistant strains of C. jejuni displayed altered supercoiling associated phenotypes. A panel of fluoroquinolone resistant mutants were derived and shown to have a greater ability to form viable biofilms under aerobic conditions, invade epithelial cells and promote virulence in the Galleria mellonella model of infection. We thus report for the first time that fluoroquinolone resistance in C. jejuni is associated with an increase in virulence and the ability to form viable biofilms in oxygen rich environments. These altered phenotypes likely play a critical role in the continued increase in fluoroquinolone resistance observed for this important pathogen.
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Affiliation(s)
- Matthew V X Whelan
- School of Biomolecular and Biomedical Science, University College Dublin, Belfield, Dublin 4, Ireland
| | - Laura Ardill
- School of Biomolecular and Biomedical Science, University College Dublin, Belfield, Dublin 4, Ireland
| | - Kentaro Koide
- Division of Bioresources, Hokkaido University Research Center for Zoonosis Control, Sapporo, Japan
| | - Chie Nakajima
- Division of Bioresources, Hokkaido University Research Center for Zoonosis Control, Sapporo, Japan
- The Global Station for Zoonosis Control, Hokkaido University Global Institution for Collaborative Research and Education, Kita 20 Nishi 10, Kita-ku, Sapporo, Japan
| | - Yasuhiko Suzuki
- Division of Bioresources, Hokkaido University Research Center for Zoonosis Control, Sapporo, Japan
- The Global Station for Zoonosis Control, Hokkaido University Global Institution for Collaborative Research and Education, Kita 20 Nishi 10, Kita-ku, Sapporo, Japan
| | - Jeremy C Simpson
- School of Biology and Environmental Science, University College Dublin, Belfield, Dublin 4, Ireland
| | - Tadhg Ó Cróinín
- School of Biomolecular and Biomedical Science, University College Dublin, Belfield, Dublin 4, Ireland.
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Rhen M. Salmonella and Reactive Oxygen Species: A Love-Hate Relationship. J Innate Immun 2019; 11:216-226. [PMID: 30943492 DOI: 10.1159/000496370] [Citation(s) in RCA: 56] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2018] [Accepted: 12/19/2018] [Indexed: 12/22/2022] Open
Abstract
Salmonella enterica represents an enterobacterial species including numerous serovars that cause infections at, or initiated at, the intestinal epithelium. Many serovars also act as facultative intracellular pathogens with a tropism for phagocytic cells. These bacteria not only survive in phagocytes but also undergo de facto replication therein. Phagocytes, through the activities of phagocyte NADPH-dependent oxidase and inducible nitric oxide synthase, are very proficient in converting molecular oxygen to reactive oxygen (ROS) and nitrogen species (RNS). These compounds represent highly efficient effectors of the innate immune defense. Salmonella is by no means resistant to these effectors, which may stand in contrast to the host niches chosen. To cope with this paradox, these bacteria rely on an array of detoxification and repair systems. Combination these systems allows for a high enough tolerance to ROS and RNS to enable establishment of infection. In addition, salmonella possesses protein factors that have the potential to dampen the infection-associated inflammation, which evidently results in a reduced exposure to ROS and RNS. This review attempts to summarize the activities and strategies by which salmonella tries to cope with ROS and RNS and how the bacterium can make use of these innate defense factors.
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Affiliation(s)
- Mikael Rhen
- Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, Stockholm, Sweden, .,Department of Molecular Biology, Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå University, Umeå, Sweden, .,Umeå Centre for Microbial Research (UCMR), Umeå University, Umeå, Sweden,
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23
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Ovesen S, Durack J, Kirk KF, Nielsen HL, Nielsen H, Lynch SV. Motility and biofilm formation of the emerging gastrointestinal pathogen Campylobacter concisus differs under microaerophilic and anaerobic environments. Gut Microbes 2018; 10:34-44. [PMID: 30252590 PMCID: PMC6363072 DOI: 10.1080/19490976.2018.1472201] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
Campylobacter concisus has been isolated from patients with gastroenteritis and inflammatory bowel disease (IBD), as well as healthy subjects. While strain differences may plausibly explain virulence differentials, an alternative hypothesis posits that the pathogenic potential of this species may depend on altered ecosystem conditions in the inflamed gut. One potential difference is oxygen availability, which is frequently increased under conditions of inflammation and is known to regulate bacterial virulence. Hence, we hypothesized that oxygen influences C. concisus physiology. We therefore characterized the effect of microaerophilic or anaerobic environments on C. concisus motility and biofilm formation, two important determinants of host colonization and dissemination. C. concisus isolates (n = 46) sourced from saliva, gut mucosal biopsies and feces of patients with IBD (n = 23), gastroenteritis (n = 8) and healthy subjects (n = 13), were used for this study. Capacity to form biofilms was determined using crystal violet assay, while assessment of dispersion through soft agar permitted motility to be assessed. No association existed between GI disease and either motility or biofilm forming capacity. Oral isolates exhibited significantly greater capacity for biofilm formation compared to fecal isolates (p<0.03), and showed a strong negative correlation between motility and biofilm formation (r = -0.7; p = 0.01). Motility significantly increased when strains were cultured under microaerophilic compared to anaerobic conditions (p<0.001). Increased biofilm formation under microaerophillic conditions was also observed for a subset of isolates. Hence, differences in oxygen availability appear to influence key physiological aspects of the opportunistic gastrointestinal pathogen C. concisus.
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Affiliation(s)
- Sandra Ovesen
- Department of Medicine, Division of Gastroenterology, University of California San Francisco, San Francisco, CA, USA,Department of Infectious Diseases, Aalborg University Hospital, Aalborg, Denmark
| | - Juliana Durack
- Department of Medicine, Division of Gastroenterology, University of California San Francisco, San Francisco, CA, USA
| | - Karina Frahm Kirk
- Department of Infectious Diseases, Aalborg University Hospital, Aalborg, Denmark
| | - Hans Linde Nielsen
- Department of Clinical Microbiology, Aalborg University Hospital, Aalborg, Denmark
| | - Henrik Nielsen
- Department of Infectious Diseases, Aalborg University Hospital, Aalborg, Denmark,Department of Clinical Medicine, Aalborg University, Aalborg, Denmark
| | - Susan V. Lynch
- Department of Medicine, Division of Gastroenterology, University of California San Francisco, San Francisco, CA, USA,CONTACT: Susan Lynch, ., Department of Medicine, Division of Gastroenterology, University of California San Francisco, San Francisco, CA 94143, USA
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24
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Oh E, Andrews KJ, Jeon B. Enhanced Biofilm Formation by Ferrous and Ferric Iron Through Oxidative Stress in Campylobacter jejuni. Front Microbiol 2018; 9:1204. [PMID: 29928267 PMCID: PMC5998592 DOI: 10.3389/fmicb.2018.01204] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2018] [Accepted: 05/17/2018] [Indexed: 12/14/2022] Open
Abstract
Campylobacter is a leading foodborne pathogen worldwide. Biofilm formation is an important survival mechanism that sustains the viability of Campylobacter under harsh stress conditions. Iron affects biofilm formation in some other bacteria; however, the effect of iron on biofilm formation has not been investigated in Campylobacter. In this study, we discovered that ferrous (Fe2+) and ferric (Fe3+) iron stimulated biofilm formation in Campylobacter jejuni. The sequestration of iron with an iron chelator prevented the iron-mediated biofilm stimulation. The level of total reactive oxygen species (ROS) in biofilms was increased by iron. However, the supplementation with an antioxidant prevented the total ROS level from being increased in biofilms by iron and also inhibited iron-mediated biofilm stimulation in C. jejuni. This suggests that iron promotes biofilm formation through oxidative stress. Based on the results of fluorescence microscopic analysis, Fe2+ and Fe3+ enhanced both microcolony formation and biofilm maturation. The levels of extracellular DNA and polysaccharides in biofilms were increased by iron supplementation. The effect of iron on biofilm formation was also investigated with 70 C. jejuni isolates from raw chicken. Regardless of the inherent levels of biofilm formation, iron stimulated biofilm formation in all tested strains; however, there were strain variations in iron concentrations affecting biofilm formation. The biofilm formation of 92.9% (65 of 70) strains was enhanced by either 40 μM Fe2+ or 20 μM Fe3+ or both (the iron concentrations that enhanced biofilm formation in C. jejuni NCTC 11168), whereas different iron concentrations were required to promote biofilms in the rest of the strains. The findings in this study showed that Fe2+ and Fe3+ contributed to the stimulation of biofilm formation in C. jejuni through oxidative stress.
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Affiliation(s)
- Euna Oh
- School of Public Health, University of Alberta, Edmonton, AB, Canada
| | - Katelyn J Andrews
- School of Public Health, University of Alberta, Edmonton, AB, Canada
| | - Byeonghwa Jeon
- School of Public Health, University of Alberta, Edmonton, AB, Canada
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25
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Gölz G, Kittler S, Malakauskas M, Alter T. Survival of Campylobacter in the Food Chain and the Environment. CURRENT CLINICAL MICROBIOLOGY REPORTS 2018. [DOI: 10.1007/s40588-018-0092-z] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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26
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Ankyrin-Like Protein AnkB Interacts with CatB, Affects Catalase Activity, and Enhances Resistance of Xanthomonas oryzae pv. oryzae and Xanthomonas oryzae pv. oryzicola to Phenazine-1-Carboxylic Acid. Appl Environ Microbiol 2018; 84:AEM.02145-17. [PMID: 29180371 DOI: 10.1128/aem.02145-17] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2017] [Accepted: 11/18/2017] [Indexed: 02/07/2023] Open
Abstract
Xanthomonas oryzae pv. oryzae, which causes rice bacterial leaf blight, and Xanthomonas oryzae pv. oryzicola, which causes rice bacterial leaf streak, are important plant-pathogenic bacteria. A member of the adaptor protein family, ankyrin protein, has been investigated largely in humans but rarely in plant-pathogenic bacteria. In this study, a novel ankyrin-like protein, AnkB, was identified in X. oryzae pv. oryzae and X. oryzae pv. oryzicola. The expression of ankB was significantly upregulated when these bacteria were treated with phenazine-1-carboxylic acid (PCA). ankB is located 58 bp downstream of the gene catB (which encodes a catalase) in both bacteria, and the gene expression of catB and catalase activity were reduced following ankB deletion in X. oryzae pv. oryzae and X. oryzae pv. oryzicola. Furthermore, we demonstrated that AnkB directly interacts with CatB by glutathione S-transferase (GST) pulldown assays. Deletion of ankB increased the sensitivity of X. oryzae pv. oryzae and X. oryzae pv. oryzicola to H2O2 and PCA, decreased bacterial biofilm formation, swimming ability, and exopolysaccharide (EPS) production, and also reduced virulence on rice. Together our results indicate that the ankyrin-like protein AnkB has important and conserved roles in antioxidant systems and pathogenicity in X. oryzae pv. oryzae and X. oryzae pv. oryzicola.IMPORTANCE This study demonstrates that the ankyrin protein AnkB directly interacts with catalase CatB in Xanthomonas oryzae pv. oryzae and Xanthomonas oryzae pv. oryzicola. Ankyrin protein AnkB can affect the gene expression of catB, catalase activity, and sensitivity to H2O2 In Xanthomonas spp., the locations of genes ankB and catB and the amino acid sequence of AnkB are highly conserved. It is suggested that in prokaryotes, AnkB plays a conserved role in the defense against oxidative stress.
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27
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Plakunov VK, Mart’yanov SV, Teteneva NA, Zhurina MV. Controlling of microbial biofilms formation: Anti- and probiofilm agents. Microbiology (Reading) 2017. [DOI: 10.1134/s0026261717040129] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
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28
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Oh E, McMullen LM, Chui L, Jeon B. Differential Survival of Hyper-Aerotolerant Campylobacter jejuni under Different Gas Conditions. Front Microbiol 2017; 8:954. [PMID: 28611753 PMCID: PMC5447730 DOI: 10.3389/fmicb.2017.00954] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2016] [Accepted: 05/12/2017] [Indexed: 01/14/2023] Open
Abstract
Campylobacter jejuni accounts for a significant number of foodborne illnesses around the world. C. jejuni is microaerophilic and typically does not survive efficiently in oxygen-rich conditions. We recently reported that hyper-aerotolerant (HAT) C. jejuni are highly prevalent in retail poultry meat. To assess the capabilities of HAT C. jejuni in foodborne transmission and infection, in this study, we investigated the prevalence of virulence genes in HAT C. jejuni and the survival in poultry meat in atmosphere at a refrigeration temperature. When we examined the prevalence of eight virulence genes in 70 C. jejuni strains from raw poultry meat, interestingly, the frequencies of detecting virulence genes were significantly higher in HAT C. jejuni strains than aerosenstive C. jejuni strains. This suggests that HAT C. jejuni would potentially be more pathogenic than aerosensitive C. jejuni. Under aerobic conditions, aerosensitive C. jejuni survived at 4°C in raw poultry meat for 3 days, whereas HAT C. jejuni survived in poultry meat for a substantially extended time; there was a five-log CFU reduction over 2 weeks. In addition, we measured the effect of other gas conditions, including N2 and CO2, on the viability of HAT C. jejuni in comparison with aerosensitive and aerotolerant strains. N2 marginally affected the viability of C. jejuni. However, CO2 significantly reduced the viability of C. jejuni both in culture media and poultry meat. Based on the results, modified atmosphere packaging using CO2 may help us to control poultry contamination with HAT C. jejuni.
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Affiliation(s)
- Euna Oh
- School of Public Health, University of Alberta, EdmontonAB, Canada
| | - Lynn M McMullen
- Department of Agricultural, Food and Nutritional Science, University of Alberta, EdmontonAB, Canada
| | - Linda Chui
- Department of Laboratory Medicine and Pathology, University of Alberta, EdmontonAB, Canada.,Provincial Laboratory for Public Health, EdmontonAB, Canada
| | - Byeonghwa Jeon
- School of Public Health, University of Alberta, EdmontonAB, Canada
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