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Cheng X, Xu X, Zhou X, Ning J. Oxidative stress response: a critical factor affecting the ecological competitiveness of Streptococcus mutans. J Oral Microbiol 2023; 16:2292539. [PMID: 38405599 PMCID: PMC10885835 DOI: 10.1080/20002297.2023.2292539] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2023] [Accepted: 12/05/2023] [Indexed: 02/27/2024] Open
Abstract
Oral microecological balance is closely associated with the development of dental caries. Oxidative stress is one of the important factors regulating the composition and structure of the oral microbial community. Streptococcus mutans is linked to the occurrence and development of dental caries. The ability of S. mutans to withstand oxidative stress affects its survival competitiveness in biofilms. The oxidative stress regulatory mechanisms of S. mutans include synthesis of reductase, regulation of metal ions uptake, regulator PerR, transcription regulator Spx, extracellular uptake of glutathione, and other related signal transduction systems. Here, we provide an overview of how S. mutans adapts to oxidative stress and its influence on oral microecology, which may offer novel options to investigate the cariogenic mechanisms of S. mutans in the oral microenvironment, and new targets for the ecological prevention and treatment of dental caries.
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Affiliation(s)
- Xingqun Cheng
- State Key Laboratory of Oral Diseases & National Center for Stomatology & National Clinical Research Center for Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - Xin Xu
- State Key Laboratory of Oral Diseases & National Center for Stomatology & National Clinical Research Center for Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - Xuedong Zhou
- State Key Laboratory of Oral Diseases & National Center for Stomatology & National Clinical Research Center for Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - Jia Ning
- Department of General Dentistry, School & Hospital of Stomatology, Tianjin Medical University, Tianjin, China
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2
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Yu S, Ma Q, Li Y, Zou J. Molecular and regulatory mechanisms of oxidative stress adaptation in Streptococcus mutans. Mol Oral Microbiol 2023; 38:1-8. [PMID: 36088636 DOI: 10.1111/omi.12388] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2022] [Revised: 07/05/2022] [Accepted: 08/29/2022] [Indexed: 12/01/2022]
Abstract
Dental caries is a chronic progressive disease, which destructs dental hard tissues under the influence of multiple factors, mainly bacteria. Streptococcus mutans is the main cariogenic bacteria. However, its cariogenic virulence is affected by environmental stress such as oxidative stress, nutrient deficiency, and low pH to some extent. Oxidative stress is one of the main stresses that S. mutans faces in oral cavity. But there are a variety of protective molecules to resist oxidative stress in S. mutans, including superoxide dismutase, nicotinamide adenine dinucleotide oxidase, Dps-like peroxide resistance protein, alkyl-hydrogen peroxide reductase, thioredoxin, glutamate-reducing protein system, and some metabolic substances. Additionally, some transcriptional regulatory factors (SloR, PerR, Rex, Spx, etc.) and two-component systems are also closely related to oxidative stress adaptation by modulating the expression of protective molecules. This review summarizes the research progress of protective molecules and regulatory mechanisms (mainly transcription factors) of oxidative stress adaptation of S. mutans.
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Affiliation(s)
- Shuxing Yu
- State key Laboratory of Oral Diseases, National Clinical Research Center for Oral Diseases, Sichuan University, Chengdu, China.,Department of Pediatric Dentistry, West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - Qizhao Ma
- State key Laboratory of Oral Diseases, National Clinical Research Center for Oral Diseases, Sichuan University, Chengdu, China.,Department of Pediatric Dentistry, West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - Yuqing Li
- State key Laboratory of Oral Diseases, National Clinical Research Center for Oral Diseases, Sichuan University, Chengdu, China
| | - Jing Zou
- State key Laboratory of Oral Diseases, National Clinical Research Center for Oral Diseases, Sichuan University, Chengdu, China.,Department of Pediatric Dentistry, West China Hospital of Stomatology, Sichuan University, Chengdu, China
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3
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Li C, Qi C, Yang S, Li Z, Ren B, Li J, Zhou X, Cai H, Xu X, Peng X. F0F1-ATPase Contributes to the Fluoride Tolerance and Cariogenicity of Streptococcus mutans. Front Microbiol 2022; 12:777504. [PMID: 35173687 PMCID: PMC8841791 DOI: 10.3389/fmicb.2021.777504] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2021] [Accepted: 12/20/2021] [Indexed: 12/30/2022] Open
Abstract
The phenotypic traits of Streptococcus mutans, such as fluoride tolerance, are usually associated with genotypic alterations. The aim of this study was to identify adaptive mutations of S. mutans to gradient fluoride concentrations and possible relationships between the mutations and fluoride tolerance. We identified a highly resistant S. mutans strain (FR1000) with a novel single nucleotide polymorphism (SNP, −36G→T) in the promoter region of F0F1-ATPase gene cluster (SMU_1527-SMU_1534) resistant to 1,000 ppm fluoride using the whole-genome Illumina PE250 sequencing. Thus, a −36G→T F0F1-ATPase promoter mutation from the parental strain S. mutans UA159 was constructed and named UA159-T. qRT-PCR showed that the F0F1-ATPase gene expression of both FR1000 and UA159-T was up-regulated, and fluoride tolerance of UA159-T was significantly improved. Complementation of Dicyclohexylcarbodiimide (DCCD), a specific inhibitor of F0F1-ATPase, increased fluoride susceptibility of FR1000 and UA159-T. Intracellular fluoride concentrations of fluoride tolerance strains were higher compared to UA159 strain as demonstrated by 18F analysis. Further validation with rat caries models showed that UA159-T caused more severe caries lesions under fluoride exposure compared with its parental UA159 strain. Overall, the identified −36G→T mutation in the promoter region of F0F1-ATPase gene drastically contributed to the fluoride tolerance and enhanced cariogenicity of S. mutans. These findings provided new insights into the mechanism of microbial fluoride tolerance, and suggested F0F1-ATPase as a potential target for suppressing fluoride resistant strains.
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Affiliation(s)
- Cheng Li
- State Key Laboratory of Oral Diseases and National Clinical Research Center for Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, China
- Department of Cariology and Endodontics, West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - Cai Qi
- State Key Laboratory of Oral Diseases and National Clinical Research Center for Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, China
- Department of Cariology and Endodontics, West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - Sirui Yang
- State Key Laboratory of Oral Diseases and National Clinical Research Center for Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, China
- Department of Cariology and Endodontics, West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - Zhengyi Li
- State Key Laboratory of Oral Diseases and National Clinical Research Center for Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - Biao Ren
- State Key Laboratory of Oral Diseases and National Clinical Research Center for Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - Jiyao Li
- State Key Laboratory of Oral Diseases and National Clinical Research Center for Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, China
- Department of Cariology and Endodontics, West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - Xuedong Zhou
- State Key Laboratory of Oral Diseases and National Clinical Research Center for Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, China
- Department of Cariology and Endodontics, West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - Huawei Cai
- Laboratory of Nuclear Medicine, Department of Clinical Nuclear Medicine, West China Hospital, Sichuan University, Chengdu, China
| | - Xin Xu
- State Key Laboratory of Oral Diseases and National Clinical Research Center for Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, China
- Department of Cariology and Endodontics, West China Hospital of Stomatology, Sichuan University, Chengdu, China
- *Correspondence: Xin Xu,
| | - Xian Peng
- State Key Laboratory of Oral Diseases and National Clinical Research Center for Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, China
- Xian Peng,
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Virulence Comparison of Salmonella enterica Subsp. enterica Isolates from Chicken and Whole Genome Analysis of the High Virulent Strain S. Enteritidis 211. Microorganisms 2021; 9:microorganisms9112239. [PMID: 34835366 PMCID: PMC8619400 DOI: 10.3390/microorganisms9112239] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2021] [Revised: 10/12/2021] [Accepted: 10/20/2021] [Indexed: 01/28/2023] Open
Abstract
Background: Salmonellaenterica is one of the common pathogens in both humans and animals that causes salmonellosis and threatens public health all over the world. Methods and Results: Here we determined the virulence phenotypes of nine Salmonellaenterica subsp. enterica (S. enterica) isolates in vitro and in vivo, including pathogenicity to chicken, cell infection, biofilm formation and virulence gene expressions. S. Enteritidis 211 (SE211) was highly pathogenic with notable virulence features among the nine isolates. The combination of multiple virulence genes contributed to the conferring of the high virulence in SE211. Importantly, many mobile genetic elements (MGEs) were found in the genome sequence of SE211, including a virulence plasmid, genomic islands, and prophage regions. The MGEs and CRISPR-Cas system might function synergistically for gene transfer and immune defense. In addition, the neighbor joining tree and the minimum spanning tree were constructed in this study. Conclusions: This study provided both the virulence phenotypes and genomic features, which might contribute to the understanding of bacterial virulence mechanisms in Salmonella enterica subsp. enterica. The first completed genomic sequence for the high virulent S. Enteritidis isolate SE211 and the comparative genomics and phylogenetic analyses provided a preliminary understanding of S. enterica genetics and laid the foundation for further study.
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The LiaFSR transcriptome reveals an interconnected regulatory network in group A Streptococcus. Infect Immun 2021; 89:e0021521. [PMID: 34370508 DOI: 10.1128/iai.00215-21] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The mechanisms by which bacteria sense the host environment and alter gene expression are poorly understood. LiaFSR is a gene regulatory system unique to Gram-positive bacteria including group A Streptococcus (GAS) and responds to cell envelope stress. We previously showed that LiaF acts as an inhibitor to LiaFSR activation in GAS. To better understand gene regulation associated with LiaFSR activation, we performed RNA-sequencing on isogenic deletion mutants fixed in a LiaFSR "always on" (ΔliaF) or "always off" (ΔliaR) state. Transcriptome analyses of ΔliaF and ΔliaR in GAS showed near perfect inverse correlation including the gene encoding the global transcriptional regulator SpxA2. In addition, mutant transcriptomes included genes encoding multiple virulence factors and showed substantial overlap with the CovRS regulon. Chromatin immunoprecipitation quantitative PCR demonstrated direct spxA2 gene regulation following activation of the response regulator, LiaR. High SpxA2 levels as a result of LiaFSR activation were directly correlated with increased CovR-regulated virulence gene transcription. Further, consistent with known virulence gene repression by phosphorylated CovR, elevated SpxA2 levels were inversely correlated with CovR phosphorylation. Despite increased transcription of several virulence factors, ΔliaF (high SpxA2) exhibited a paradoxical virulence phenotype in both in vivo mouse and ex vivo human blood models of disease. Likewise, despite decreased virulence factor transcription in ΔliaR (low SpxA2), increased virulence was observed in an in vivo mouse model of disease - a phenotype attributable, in part, to known SpxA2-associated speB transcription. Our findings provide evidence of a critical role of LiaFSR in sensing the host environment and suggest a potential mechanism for gene regulatory system crosstalk shared by many Gram-positive pathogens.
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André CB, Rosalen PL, Giannini M, Bueno-Silva B, Pfeifer CS, Ferracane JL. Incorporation of Apigenin and tt-Farnesol into dental composites to modulate the Streptococcus mutans virulence. Dent Mater 2021; 37:e201-e212. [PMID: 33422299 PMCID: PMC7981265 DOI: 10.1016/j.dental.2020.12.005] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2020] [Revised: 12/05/2020] [Accepted: 12/22/2020] [Indexed: 11/30/2022]
Abstract
OBJECTIVES The aim of this in vitro study was to incorporate two anti-caries agents, Apigenin and tt-Farnesol, to resin composite and resin cement to reduce the virulence of Streptococcus mutans around dental restorations. METHODS Apigenin (Api, 5 mM) and tt-Farnesol (Far, 5 mM) were added alone, together, and combined with fluoride (F). Biofilm of S. mutans was grown on composite discs, and the dry-weight, bacterial viability, and the polysaccharides (alkali-soluble, intracellular and water-soluble) were quantified. CLSM images of the S. mutans biofilm were obtained after three years of water-storage. The effect of the additions on the physicochemical properties and the composite colorimetric parameters were also analyzed. RESULTS The additions did not affect bacterial viability. Api alone and combined with Far or combined with Far and F decreased the bacterial dry-weight, alkali-soluble and intracellular polysaccharides. After three years, the composites containing the additions presented a greater EPS matrix on the top of biofilm. Statistical difference was obtained for the degree of conversion; however, the maximum polymerization rate and curing kinetics were unaffected by the additions. No difference was observed for the water-soluble polysaccharides, flexural strength, and elastic modulus. Api increased the yellowness of the composites. SIGNIFICANCE Api, alone and combined, reduced the expression of virulence of S. mutans without jeopardizing the physicochemical properties of the composites.
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Affiliation(s)
- Carolina Bosso André
- Department of Restorative Dentistry, School of Dentistry, Federal University of Minas Gerais, Belo Horizonte, MG, Brazil.
| | - Pedro Luiz Rosalen
- Department of Biosciences, Piracicaba Dental School, University of Campinas, Piracicaba, SP, Brazil; Biological Sciences Graduate Program, Federal University of Alfenas, Alfenas, MG, Brazil.
| | - Marcelo Giannini
- Department of Restorative Dentistry, Piracicaba Dental School, University of Campinas, Piracicaba, SP, Brazil.
| | - Bruno Bueno-Silva
- Dental Research Division, School of Dentistry, Guarulhos University, Guarulhos, SP, Brazil.
| | - Carmem Silvia Pfeifer
- Department of Biomaterials and Biomechanics, School of Dentistry, Oregon Health & Science University, Portland, OR, USA.
| | - Jack Liborio Ferracane
- Department of Biomaterials and Biomechanics, School of Dentistry, Oregon Health & Science University, Portland, OR, USA.
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Shanmugam K, Sarveswari HB, Udayashankar A, Swamy SS, Pudipeddi A, Shanmugam T, Solomon AP, Neelakantan P. Guardian genes ensuring subsistence of oral Streptococcus mutans. Crit Rev Microbiol 2020; 46:475-491. [PMID: 32720594 DOI: 10.1080/1040841x.2020.1796579] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Despite the substantial research advancements on oral diseases, dental caries remains a major healthcare burden. A disease of microbial dysbiosis, dental caries is characterised by the formation of biofilms that assist demineralisation and destruction of the dental hard tissues. While it is well understood that this is a multi-kingdom biofilm-mediated disease, it has been elucidated that acid producing and acid tolerant bacteria play pioneering roles in the process. Specifically, Streptococcus mutans houses major virulence pathways that enable it to thrive in the oral cavity and cause caries. This pathogen adheres to the tooth substrate, forms biofilms, resists external stress, produces acids, kills closely related species, and survives the acid as well as the host clearance mechanisms. For an organism to be able to confer such virulence, it requires a large and complex gene network which synergise to establish disease. In this review, we have charted how these multi-faceted genes control several caries-related functions of Streptococcus mutans. In a futuristic thinking approach, we also briefly discuss the potential roles of omics and machine learning, to ease the study of non-functional genes that may play a major role and enable the integration of experimental data.
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Affiliation(s)
- Karthi Shanmugam
- Quorum Sensing Laboratory, Centre for Research in Infectious Diseases (CRID), School of Chemical and Biotechnology, SASTRA Deemed to be University, Thanjavur, India
| | - Hema Bhagavathi Sarveswari
- Quorum Sensing Laboratory, Centre for Research in Infectious Diseases (CRID), School of Chemical and Biotechnology, SASTRA Deemed to be University, Thanjavur, India
| | - Akshaya Udayashankar
- Quorum Sensing Laboratory, Centre for Research in Infectious Diseases (CRID), School of Chemical and Biotechnology, SASTRA Deemed to be University, Thanjavur, India
| | - Shogan Sugumar Swamy
- Quorum Sensing Laboratory, Centre for Research in Infectious Diseases (CRID), School of Chemical and Biotechnology, SASTRA Deemed to be University, Thanjavur, India
| | - Akhila Pudipeddi
- Quorum Sensing Laboratory, Centre for Research in Infectious Diseases (CRID), School of Chemical and Biotechnology, SASTRA Deemed to be University, Thanjavur, India
| | - Tamilarasi Shanmugam
- Quorum Sensing Laboratory, Centre for Research in Infectious Diseases (CRID), School of Chemical and Biotechnology, SASTRA Deemed to be University, Thanjavur, India
| | - Adline Princy Solomon
- Quorum Sensing Laboratory, Centre for Research in Infectious Diseases (CRID), School of Chemical and Biotechnology, SASTRA Deemed to be University, Thanjavur, India
| | - Prasanna Neelakantan
- Division of Restorative Dental Sciences, Faculty of Dentistry, The University of Hong Kong, Hong Kong, Hong Kong
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Ganguly T, Kajfasz JK, Abranches J, Lemos JA. Regulatory circuits controlling Spx levels in Streptococcus mutans. Mol Microbiol 2020; 114:109-126. [PMID: 32189382 DOI: 10.1111/mmi.14499] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2019] [Revised: 03/13/2020] [Accepted: 03/14/2020] [Indexed: 02/01/2023]
Abstract
Spx is a major regulator of stress responses in Firmicutes. In Streptococcus mutans, two Spx homologues, SpxA1 and SpxA2, were identified as mediators of oxidative stress responses but the regulatory circuits controlling their levels and activity are presently unknown. Comparison of SpxA1 and SpxA2 protein sequences revealed differences at the C-terminal end, with SpxA1 containing an unusual number of acidic residues. Here, we showed that a green fluorescence protein (GFP) reporter becomes unstable when fused to the last 10 amino acids of SpxA2 but remained stable when fused to the C-terminal acidic tail of SpxA1. Inactivation of clpP or simultaneous inactivation of clpC and clpE stabilized the GFP::SpxA2tail fusion protein. Addition of acidic amino acids to the GFP::SpxA2tail chimera stabilized GFP, while deletion of the acidic residues destabilized GFP::SpxA1tail . Promoter reporter fusions revealed that spxA1 transcription is co-repressed by the metalloregulators PerR and SloR while spxA2 transcription is largely dependent on the envelope stress regulator LiaFSR. In agreement with spxA2 being part of the LiaR regulon, SpxA2 was found to be critical for the growth of S. mutans under envelope stress conditions. Finally, we showed that redox sensing is essential for SpxA1-dependent activation of oxidative stress responses but dispensable for SpxA2-mediated envelope stress responses.
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Affiliation(s)
- Tridib Ganguly
- Department of Oral Biology, College of Dentistry, University of Florida, Gainesville, FL, USA
| | - Jessica K Kajfasz
- Department of Oral Biology, College of Dentistry, University of Florida, Gainesville, FL, USA
| | - Jacqueline Abranches
- Department of Oral Biology, College of Dentistry, University of Florida, Gainesville, FL, USA
| | - José A Lemos
- Department of Oral Biology, College of Dentistry, University of Florida, Gainesville, FL, USA
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Baker JL, Saputo S, Faustoferri RC, Quivey RG. Streptococcus mutans SpxA2 relays the signal of cell envelope stress from LiaR to effectors that maintain cell wall and membrane homeostasis. Mol Oral Microbiol 2020; 35:118-128. [PMID: 32043713 DOI: 10.1111/omi.12282] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2019] [Revised: 02/05/2020] [Accepted: 02/06/2020] [Indexed: 12/01/2022]
Abstract
Streptococcus mutans is a major etiologic agent of dental caries, which is the most common chronic infectious disease worldwide. S. mutans is particularly adept at causing caries due to its exceptional capacity to form biofilms and its ability to survive acidic conditions that arrest acid production and growth in many more benign members of the oral microbiota. Two mechanisms utilized by S. mutans to tolerate acid are: modulation of the membrane fatty acid content and utilization of the F1 F0 -ATPase to pump protons out of the cytosol. In this study, the role of the spxA2 transcriptional regulator in these two pathways, and overall cell envelope homeostasis, was examined. Loss of spxA2 resulted in an increase in the proportion of saturated fatty acids in the S. mutans membrane and altered transcription of several genes involved in the production of these membrane fatty acids, including fabT and fabM. Furthermore, activity of the F1 F0 -ATPase was increased in the ∆spxA2 strain. Transcription of spxA2 was elevated in the presence of a variety of membrane stressors, and highly dependent on the liaR component of the LiaFSR system, which is known to sense cell envelope stress in many Gram-positive bacteria. Finally, deletion of ∆spxA2 led to altered susceptibility of S. mutans to membrane stressors. Overall, the results of this study indicate that spxA2 serves a crucial role in transmitting the signal of cell wall/membrane damage from the LiaFSR sensor to downstream effectors in the SpxA2 regulon which restore and maintain membrane and cell wall homeostasis.
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Affiliation(s)
- Jonathon L Baker
- Genomic Medicine Group, J. Craig Venter Institute, La Jolla, CA, USA
| | - Sarah Saputo
- Center for Oral Biology, Box 611, University of Rochester School of Medicine and Dentistry, Rochester, NY, USA
| | - Roberta C Faustoferri
- Center for Oral Biology, Box 611, University of Rochester School of Medicine and Dentistry, Rochester, NY, USA
| | - Robert G Quivey
- Center for Oral Biology, Box 611, University of Rochester School of Medicine and Dentistry, Rochester, NY, USA
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Cui L, Wang X, Huang D, Zhao Y, Feng J, Lu Q, Pu Q, Wang Y, Cheng G, Wu M, Dai M. CRISPR- cas3 of Salmonella Upregulates Bacterial Biofilm Formation and Virulence to Host Cells by Targeting Quorum-Sensing Systems. Pathogens 2020; 9:pathogens9010053. [PMID: 31936769 PMCID: PMC7168661 DOI: 10.3390/pathogens9010053] [Citation(s) in RCA: 42] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2019] [Revised: 01/05/2020] [Accepted: 01/07/2020] [Indexed: 12/16/2022] Open
Abstract
Salmonella is recognized as one of the most common microbial pathogens worldwide. The bacterium contains the clustered regularly interspaced short palindromic repeats (CRISPR)-CRISPR-associated (Cas) systems, providing adaptive immunity against invading foreign nucleic acids. Previous studies suggested that certain bacteria employ the Cas proteins of CRISPR-Cas systems to target their own genes, which also alters the virulence during invasion of mammals. However, whether CRISPR-Cas systems in Salmonella have similar functions during bacterial invasion of host cells remains unknown. Here, we systematically analyzed the genes that are regulated by Cas3 in a type I-E CRISPR-Cas system and the virulence changes due to the deletion of cas3 in Salmonella enterica serovar Enteritidis. Compared to the cas3 gene wild-type (cas3 WT) Salmonella strain, cas3 deletion upregulated the lsrFGBE genes in lsr (luxS regulated) operon related to quorum sensing (QS) and downregulated biofilm-forming-related genes and Salmonella pathogenicity island 1 (SPI-1) genes related to the type three secretion system (T3SS). Consistently, the biofilm formation ability was downregulated in the cas3 deletion mutant (Δcas3). The bacterial invasive and intracellular capacity of Δcas3 to host cells was also reduced, thereby increasing the survival of infected host cells and live chickens. By the transcriptome-wide screen (RNA-Seq), we found that the cas3 gene impacts a series of genes related to QS, the flagellum, and SPI-1-T3SS system, thereby altering the virulence phenotypes. As QS SPI-1-T3SS and CRISPR-Cas systems are widely distributed in the bacteria kingdom, our findings extend our understanding of virulence regulation and pathogenicity in mammalian hosts for Salmonella and potentially other bacteria.
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Affiliation(s)
- Luqing Cui
- The Cooperative Innovation Center for Sustainable Pig Production, Huazhong Agricultural University, Wuhan 430070, China; (L.C.); (X.W.); (Y.Z.); (J.F.)
- Department of Biomedical Sciences, University of North Dakota School of Medicine and Health Sciences, Grand Forks, ND 58203, USA;
| | - Xiangru Wang
- The Cooperative Innovation Center for Sustainable Pig Production, Huazhong Agricultural University, Wuhan 430070, China; (L.C.); (X.W.); (Y.Z.); (J.F.)
| | - Deyu Huang
- MOA Key Laboratory of Food Safety Evaluation/National Reference Laboratory of Veterinary Drug Residue (HZAU), Huazhong Agricultural University, Wuhan 430070, China; (D.H.); (Q.L.); (Y.W.); (G.C.)
| | - Yue Zhao
- The Cooperative Innovation Center for Sustainable Pig Production, Huazhong Agricultural University, Wuhan 430070, China; (L.C.); (X.W.); (Y.Z.); (J.F.)
| | - Jiawei Feng
- The Cooperative Innovation Center for Sustainable Pig Production, Huazhong Agricultural University, Wuhan 430070, China; (L.C.); (X.W.); (Y.Z.); (J.F.)
| | - Qirong Lu
- MOA Key Laboratory of Food Safety Evaluation/National Reference Laboratory of Veterinary Drug Residue (HZAU), Huazhong Agricultural University, Wuhan 430070, China; (D.H.); (Q.L.); (Y.W.); (G.C.)
| | - Qinqin Pu
- Department of Biomedical Sciences, University of North Dakota School of Medicine and Health Sciences, Grand Forks, ND 58203, USA;
| | - Yulian Wang
- MOA Key Laboratory of Food Safety Evaluation/National Reference Laboratory of Veterinary Drug Residue (HZAU), Huazhong Agricultural University, Wuhan 430070, China; (D.H.); (Q.L.); (Y.W.); (G.C.)
| | - Guyue Cheng
- MOA Key Laboratory of Food Safety Evaluation/National Reference Laboratory of Veterinary Drug Residue (HZAU), Huazhong Agricultural University, Wuhan 430070, China; (D.H.); (Q.L.); (Y.W.); (G.C.)
| | - Min Wu
- Department of Biomedical Sciences, University of North Dakota School of Medicine and Health Sciences, Grand Forks, ND 58203, USA;
- Correspondence: (M.W.); (M.D.); Tel.: +1-701-777-4875 (M.W.); +86-027-8767-2232 (M.D.); Fax: +1-701-777-2382 (M.W.); +86-027-8767-2232 (M.D.)
| | - Menghong Dai
- The Cooperative Innovation Center for Sustainable Pig Production, Huazhong Agricultural University, Wuhan 430070, China; (L.C.); (X.W.); (Y.Z.); (J.F.)
- Correspondence: (M.W.); (M.D.); Tel.: +1-701-777-4875 (M.W.); +86-027-8767-2232 (M.D.); Fax: +1-701-777-2382 (M.W.); +86-027-8767-2232 (M.D.)
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Effects of Norspermidine on Dual-Species Biofilms Composed of Streptococcus mutans and Streptococcus sanguinis. BIOMED RESEARCH INTERNATIONAL 2019; 2019:1950790. [PMID: 31781595 PMCID: PMC6874952 DOI: 10.1155/2019/1950790] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/03/2019] [Accepted: 09/30/2019] [Indexed: 02/05/2023]
Abstract
The present study aimed at investigating the influence of norspermidine on the formation of dual-species biofilms composed of Streptococcus mutans (S. mutans) and Streptococcus sanguinis (S. sanguinis). Crystal violet assay was conducted to assess the formation of single-species biofilms of S. mutans and S. sanguinis, and the growth curve was carefully observed to monitor the growth of these two species of bacteria. Fluorescence in situ hybridization (FISH) and MTT array were used to analyze the composition and metabolic activity of the dual-species biofilms, respectively. Extracellular polysaccharides (EPS)/bacteria staining, anthrone method, and scanning electron microscopy (SEM) imaging were conducted to study the synthesis of EPS by dual-species biofilms. Lactic acid assay and pH were measured to detect dual-species biofilm acid production. We found that norspermidine had different effects on S. mutans and S. sanguinis including their growth and biofilm formation. Norspermidine regulated the composition of the dual-species biofilms, decreased the ratio of S. mutans in dual-species biofilms, and reduced the metabolic activity, EPS synthesis, and acid production of dual-species biofilms. Norspermidine regulated dual-species biofilms in an ecological way, suggesting that it may be a potent reagent for controlling dental biofilms and managing dental caries.
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Rojas-Tapias DF, Helmann JD. Roles and regulation of Spx family transcription factors in Bacillus subtilis and related species. Adv Microb Physiol 2019; 75:279-323. [PMID: 31655740 DOI: 10.1016/bs.ampbs.2019.05.003] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Bacillus subtilis Spx is the prototype for a large family of redox-responsive transcription factors found in many bacteria, most notably those from the phylum Firmicutes. Unusually for a transcription factor, B. subtilis Spx protein modulates gene expression by binding as a monomer to the αCTD domain of RNA polymerase (RNAP), and only interacts with DNA during subsequent promoter engagement. B. subtilis Spx drives the expression of a large regulon in response to proteotoxic conditions, such as heat and disulfide stress, as well as cell wall stress. Here, we review the detailed mechanisms that control the expression, stability, and activity of Spx in response to a variety of stress conditions. We also summarize current knowledge regarding Spx homologs in other Firmicutes, the environmental conditions in which those homologs are activated, and their biological role.
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Affiliation(s)
| | - John D Helmann
- Department of Microbiology, Cornell University, Ithaca, NY, United States
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Deletion of cas3 gene in Streptococcus mutans affects biofilm formation and increases fluoride sensitivity. Arch Oral Biol 2019; 99:190-197. [PMID: 30731369 DOI: 10.1016/j.archoralbio.2019.01.016] [Citation(s) in RCA: 36] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2018] [Revised: 01/12/2019] [Accepted: 01/26/2019] [Indexed: 02/05/2023]
Abstract
OBJECTIVE The goal of this study was to analyze the impact of cas3 gene on the biofilm formation and virulence gene expression in S. mutans, since our previous studies have found a connection between CRISPR/Cas systems and biofilm formation in S. mutans. METHODS The cas3 gene in-frame deletion strains of S. mutans UA159 was constructed by a two-step transformation procedure and the cas3 mutant strain was complemented in trans. The biofilm biomass was measured by crystal violet staining, and the synthesis of exopolysaccharides (EPS) was measured by the anthrone-sulfuric method. Biofilm analysis and structural imaging was using confocal laser scanning microscope (CLSM) and scanning electron microscope (SEM) assays. The fluorescence in situ hybridization (FISH) was used to analyze the spatiotemporal interactions between S. mutans and Streptococcus sanguinis. Fluoride sensitivity was determined using fluoride tolerance assays. The expression of biofilm formation related genes was evaluated by qRT-PCR. RESULTS Our results showed that S. mutans cas3 deletion strain formed less biofilm and became less competitive when it was co-cultured with S. sanguinis under fluoride treatment. The expression levels of virulence genes including vicR, gtfC, smu0630 and comDE were significantly downregulated. CONCLUSIONS The cas3 gene in S. mutans could regulate biofilm formation and fluoride resistance, consequently affecting S. mutans competitiveness in a dual-species biofilm model under fluoride treatment. These results also provide a potential strategy for enhancing fluoride specificity, with cas3 gene as a potential genetic target in the modulation of oral microecology and the treatment of dental caries.
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Nilsson M, Jakobsen TH, Givskov M, Twetman S, Tolker-Nielsen T. Oxidative stress response plays a role in antibiotic tolerance of Streptococcus mutans biofilms. MICROBIOLOGY-SGM 2019; 165:334-342. [PMID: 30663959 DOI: 10.1099/mic.0.000773] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Knowledge about biofilm-associated antibiotic tolerance mechanisms is warranted in order to develop effective treatments against biofilm infections. We performed a screen of a Streptococcus mutans transposon mutant library for mutants with reduced biofilm-associated antimicrobial tolerance, and found that the spxA1 gene plays a role in tolerance towards gentamicin and other antibiotics such as vancomycin and linezolid. SpxA1 is a regulator of genes involved in the oxidative stress response in S. mutans. The oxidative stress response genes gor and ahpC were found to be up-regulated upon antibiotic treatment of S. mutans wild-type biofilms, but not spxA1 mutant biofilms. The gor gene product catalyses the formation of glutathione which functions as an important antioxidant during oxidative stress, and accordingly biofilm-associated antibiotic tolerance of the spxA1 mutant could be restored by exogenous addition of glutathione. Our results indicate that the oxidative stress response plays a role in biofilm-associated antibiotic tolerance of S. mutans, and add to the on-going debate on the role of reactive oxygen species in antibiotic mediated killing of bacteria.
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Affiliation(s)
- Martin Nilsson
- 1Department of Immunology and Microbiology, Costerton Biofilm Center, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Tim Holm Jakobsen
- 1Department of Immunology and Microbiology, Costerton Biofilm Center, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Michael Givskov
- 1Department of Immunology and Microbiology, Costerton Biofilm Center, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
- 2Singapore Centre for Environmental Life Sciences Engineering, Nanyang Technological University, Singapore
| | - Svante Twetman
- 3Department of Odontology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Tim Tolker-Nielsen
- 1Department of Immunology and Microbiology, Costerton Biofilm Center, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
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Lemos JA, Palmer SR, Zeng L, Wen ZT, Kajfasz JK, Freires IA, Abranches J, Brady LJ. The Biology of Streptococcus mutans. Microbiol Spectr 2019; 7:10.1128/microbiolspec.GPP3-0051-2018. [PMID: 30657107 PMCID: PMC6615571 DOI: 10.1128/microbiolspec.gpp3-0051-2018] [Citation(s) in RCA: 287] [Impact Index Per Article: 57.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2018] [Indexed: 12/30/2022] Open
Abstract
As a major etiological agent of human dental caries, Streptococcus mutans resides primarily in biofilms that form on the tooth surfaces, also known as dental plaque. In addition to caries, S. mutans is responsible for cases of infective endocarditis with a subset of strains being indirectly implicated with the onset of additional extraoral pathologies. During the past 4 decades, functional studies of S. mutans have focused on understanding the molecular mechanisms the organism employs to form robust biofilms on tooth surfaces, to rapidly metabolize a wide variety of carbohydrates obtained from the host diet, and to survive numerous (and frequent) environmental challenges encountered in oral biofilms. In these areas of research, S. mutans has served as a model organism for ground-breaking new discoveries that have, at times, challenged long-standing dogmas based on bacterial paradigms such as Escherichia coli and Bacillus subtilis. In addition to sections dedicated to carbohydrate metabolism, biofilm formation, and stress responses, this article discusses newer developments in S. mutans biology research, namely, how S. mutans interspecies and cross-kingdom interactions dictate the development and pathogenic potential of oral biofilms and how next-generation sequencing technologies have led to a much better understanding of the physiology and diversity of S. mutans as a species.
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Affiliation(s)
- JA Lemos
- Department of Oral Biology, University of Florida College of Dentistry, Gainesville, FL
| | - SR Palmer
- Division of Biosciences, College of Dentistry, Ohio State University, Columbus, OH
| | - L Zeng
- Department of Oral Biology, University of Florida College of Dentistry, Gainesville, FL
| | - ZT Wen
- Dapartment of Comprehensive Dentistry and Biomaterials and Department of Microbiology, Immunology and Parasitology, Louisiana State University Health Sciences Center, New Orleans, LA
| | - JK Kajfasz
- Department of Oral Biology, University of Florida College of Dentistry, Gainesville, FL
| | - IA Freires
- Department of Oral Biology, University of Florida College of Dentistry, Gainesville, FL
| | - J Abranches
- Department of Oral Biology, University of Florida College of Dentistry, Gainesville, FL
| | - LJ Brady
- Department of Oral Biology, University of Florida College of Dentistry, Gainesville, FL
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Characterization of the Trehalose Utilization Operon in Streptococcus mutans Reveals that the TreR Transcriptional Regulator Is Involved in Stress Response Pathways and Toxin Production. J Bacteriol 2018; 200:JB.00057-18. [PMID: 29632089 DOI: 10.1128/jb.00057-18] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2018] [Accepted: 03/30/2018] [Indexed: 11/20/2022] Open
Abstract
Streptococcus mutans, the organism most frequently associated with the development of dental caries, is able to utilize a diverse array of carbohydrates for energy metabolism. One such molecule is trehalose, a disaccharide common in human foods, which has been recently implicated in enhancing the virulence of epidemic strains of the pathogen Clostridium difficile In this study, mutants with deletions of all three genes in the putative S. mutans trehalose utilization operon were characterized, and the genes were shown to be required for wild-type levels of growth when trehalose was the only carbohydrate source provided. Interestingly, the TreR transcriptional regulator appeared to be critical for responding to oxidative stress and for mounting a protective stress tolerance response following growth at moderately acidic pH. mRNA sequencing (RNA-seq) of a treR deletion mutant suggested that in S. mutans, TreR acts as a trehalose-sensing activator of transcription of the tre operon, rather than as a repressor, as described in other species. In addition, deletion of treR caused the downregulation of a number of genes involved in genetic competence and bacteriocin production, supporting the results of a recent study linking trehalose and the S. mutans competence pathways. Finally, deletion of treR compromised the ability of S. mutans to inhibit the growth of the competing species Streptococcus gordonii and Lactococcus lactis Taking the results together, this study solidifies the role of the S. mutans tre operon in trehalose utilization and suggests novel functions for the TreR regulator, including roles in the stress response and competitive fitness.IMPORTANCES. mutans is the primary etiologic agent of dental caries, which globally is the most common chronic disease. S. mutans must be able to outcompete commensal organisms in its dental plaque niche in order to establish persistence and pathogenesis. To that end, S. mutans metabolizes a diverse array of carbohydrates to generate acid and impede its acid-sensitive neighbors. Additionally, S. mutans utilizes quorum signaling through genetic competence-associated pathways to induce production of toxins to kill its rivals. This study definitively shows that the S. mutans trehalose utilization operon is required for growth in trehalose. Furthermore, this study suggests that the S. mutans TreR transcriptional regulator has a novel role in virulence through regulation of genes involved in genetic competence and toxin production.
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Liu S, Wu T, Zhou X, Zhang B, Huo S, Yang Y, Zhang K, Cheng L, Xu X, Li M. Nicotine is a risk factor for dental caries: An in vivo study. J Dent Sci 2018; 13:30-36. [PMID: 30895091 PMCID: PMC6388820 DOI: 10.1016/j.jds.2017.09.006] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2017] [Revised: 08/11/2017] [Indexed: 02/05/2023] Open
Abstract
Background/purpose Streptococcus mutans is an important pathogen in the development of dental caries. Many studies have focused on the relationship between nicotine and S. mutans in vitro. The aim of this study was to investigate the effect of nicotine on the growth of S. mutans and its cariogenic potential in vivo. Materials and methods Sixteen male Specific-pathogen-free Wistar rats were divided into 2 groups (nicotine-treated and nicotine-untreated group) and infected with S. mutans. The S. mutans suspension was treated with 1 mg/mL nicotine in the nicotine-treated group. The Keyes method was used to evaluate sulcal caries of rats, and dental plaque on molar teeth was observed by scanning electron microscopy (SEM). Results Incidence of sulcal caries was higher in nicotine-treated group compared to nicotine-untreated group (42.7 ± 1.7 vs 37.3 ± 4.9, P = 0.009). Severity of caries increased with nicotine treatment. The slightly dentinal caries scores and moderate dentinal caries scores were higher in the presence of nicotine (P < 0.001). Increased number of S. mutans cells attached to dental surface was observed under SEM in the nicotine-treated group. Conclusion Nicotine would promote the attachment of S. mutans to dental surface, and further increase the incidence and severity of dental caries. Therefore, nicotine might be a risk factor for smoking-induced caries.
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Affiliation(s)
- Shiyu Liu
- State Key Laboratory of Oral Diseases, Sichuan University, Chengdu, China
- Department of Operative Dentistry and Endodontics, West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - Tianmu Wu
- State Key Laboratory of Oral Diseases, Sichuan University, Chengdu, China
- Department of Operative Dentistry and Endodontics, West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - Xuedong Zhou
- State Key Laboratory of Oral Diseases, Sichuan University, Chengdu, China
- Department of Operative Dentistry and Endodontics, West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - Bo Zhang
- Department of Operative Dentistry and Endodontics, West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - Sibei Huo
- Department of Operative Dentistry and Endodontics, West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - Yutao Yang
- Department of Operative Dentistry and Endodontics, West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - Keke Zhang
- State Key Laboratory of Oral Diseases, Sichuan University, Chengdu, China
| | - Lei Cheng
- State Key Laboratory of Oral Diseases, Sichuan University, Chengdu, China
- Department of Operative Dentistry and Endodontics, West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - Xin Xu
- State Key Laboratory of Oral Diseases, Sichuan University, Chengdu, China
- Department of Operative Dentistry and Endodontics, West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - Mingyun Li
- State Key Laboratory of Oral Diseases, Sichuan University, Chengdu, China
- Corresponding author. State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, China.
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André CB, Rosalen PL, Galvão LCDC, Fronza BM, Ambrosano GMB, Ferracane JL, Giannini M. Modulation of Streptococcus mutans virulence by dental adhesives containing anti-caries agents. Dent Mater 2017; 33:1084-1092. [DOI: 10.1016/j.dental.2017.07.006] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2017] [Revised: 06/12/2017] [Accepted: 07/08/2017] [Indexed: 01/13/2023]
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André CB, Dos Santos A, Pfeifer CS, Giannini M, Girotto EM, Ferracane JL. Evaluation of three different decontamination techniques on biofilm formation, and on physical and chemical properties of resin composites. J Biomed Mater Res B Appl Biomater 2017; 106:945-953. [PMID: 28440891 DOI: 10.1002/jbm.b.33907] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2016] [Revised: 03/27/2017] [Accepted: 04/13/2017] [Indexed: 12/29/2022]
Abstract
OBJECTIVES This study evaluated three different sterilization/disinfection techniques for resin composites on bacterial growth and surface modification after decontamination. METHODS Two resin composites were sterilized/disinfected with three different techniques: UV light, 1% chloramine T, and 70% ethanol. Four different times were used for each technique to determine the shortest time that the solution or UV light was effective. The influence of sterilization/disinfection technique on bacterial growth was evaluated by analyzing the metabolic activity, using the AlamarBlue™ assay, bacterial viability, and SEM images from biofilms of Streptococcus mutans. The surface change, after the process, was analyzed with ATR/FTIR and SEM images. The solutions used for decontamination (1% chloramine-T and 70% ethanol) were analyzed with 1 H-NMR to identify any resin compounds leached during the process. RESULTS One minute of decontamination was efficient for all three methods tested. Chloramine-T increased the surface porosity on resin composites, no changes were observed for UV light and 70% ethanol, however, 1 H-NMR identified leached monomers only when 70% ethanol was used. No chemical change of the materials was found under ATR/FTIR analyses after the decontamination process. Chloramine-T, with no previous wash, increased the bacterial viability for both resin composites and increased the bacterial metabolism for the resin composite without fluoride. CONCLUSION UV light had no interference on the resin composites properties tested using 1 min of exposure compared to the other decontamination methods. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 945-953, 2018.
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Affiliation(s)
- Carolina Bosso André
- Department of Restorative Dentistry, Piracicaba Dental School, University of Campinas, Campinas, Brazil
| | - Andressa Dos Santos
- Department of Chemistry, School of Chemistry, State University of Maringá, Maringá, Brazil
| | - Carmem Silvia Pfeifer
- Department of Dental Materials, School of Dentistry, Oregon Health and Science University, Portland, Oregon
| | - Marcelo Giannini
- Department of Restorative Dentistry, Piracicaba Dental School, University of Campinas, Campinas, Brazil
| | | | - Jack Liborio Ferracane
- Department of Dental Materials, School of Dentistry, Oregon Health and Science University, Portland, Oregon
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A Redox-Responsive Transcription Factor Is Critical for Pathogenesis and Aerobic Growth of Listeria monocytogenes. Infect Immun 2017; 85:IAI.00978-16. [PMID: 28193635 PMCID: PMC5400837 DOI: 10.1128/iai.00978-16] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2016] [Accepted: 02/07/2017] [Indexed: 11/25/2022] Open
Abstract
Bacterial pathogens have evolved sophisticated mechanisms to sense and adapt to redox stress in nature and within the host. However, deciphering the redox environment encountered by intracellular pathogens in the mammalian cytosol is challenging, and that environment remains poorly understood. In this study, we assessed the contributions of the two redox-responsive, Spx-family transcriptional regulators to the virulence of Listeria monocytogenes, a Gram-positive facultative intracellular pathogen. Spx-family proteins are highly conserved in Firmicutes, and the L. monocytogenes genome contains two paralogues, spxA1 and spxA2. Here, we demonstrate that spxA1, but not spxA2, is required for the oxidative stress response and pathogenesis. SpxA1 function appeared to be conserved with the Bacillus subtilis homologue, and resistance to oxidative stress required the canonical CXXC redox-sensing motif. Remarkably, spxA1 was essential for aerobic growth, demonstrating that L. monocytogenes SpxA1 likely regulates a distinct set of genes. Although the ΔspxA1 mutant did not grow in the presence of oxygen in the laboratory, it was able to replicate in macrophages and colonize the spleens, but not the livers, of infected mice. These data suggest that the redox state of bacteria during infection differs significantly from that of bacteria growing in vitro. Further, the host cell cytosol may resemble an anaerobic environment, with tissue-specific variations in redox stress and oxygen concentration.
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Evidence that Oxidative Stress Induces spxA2 Transcription in Bacillus anthracis Sterne through a Mechanism Requiring SpxA1 and Positive Autoregulation. J Bacteriol 2016; 198:2902-2913. [PMID: 27501985 PMCID: PMC5055595 DOI: 10.1128/jb.00512-16] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2016] [Accepted: 08/02/2016] [Indexed: 12/22/2022] Open
Abstract
Bacillus anthracis possesses two paralogs of the transcriptional regulator, Spx. SpxA1 and SpxA2 interact with RNA polymerase (RNAP) to activate the transcription of genes implicated in the prevention and alleviation of oxidative protein damage. The spxA2 gene is highly upregulated in infected macrophages, but how this is achieved is unknown. Previous studies have shown that the spxA2 gene was under negative control by the Rrf2 family repressor protein, SaiR, whose activity is sensitive to oxidative stress. These studies also suggested that spxA2 was under positive autoregulation. In the present study, we show by in vivo and in vitro analyses that spxA2 is under direct autoregulation but is also dependent on the SpxA1 paralogous protein. The deletion of either spxA1 or spxA2 reduced the diamide-inducible expression of an spxA2-lacZ construct. In vitro transcription reactions using purified B. anthracis RNAP showed that SpxA1 and SpxA2 protein stimulates transcription from a DNA fragment containing the spxA2 promoter. Ectopically positioned spxA2-lacZ fusion requires both SpxA1 and SpxA2 for expression, but the requirement for SpxA1 is partially overcome when saiR is deleted. Electrophoretic mobility shift assays showed that SpxA1 and SpxA2 enhance the affinity of RNAP for spxA2 promoter DNA and that this activity is sensitive to reductant. We hypothesize that the previously observed upregulation of spxA2 in the oxidative environment of the macrophage is at least partly due to SpxA1-mediated SaiR repressor inactivation and the positive autoregulation of spxA2 transcription. IMPORTANCE Regulators of transcription initiation are known to govern the expression of genes required for virulence in pathogenic bacterial species. Members of the Spx family of transcription factors function in control of genes required for virulence and viability in low-GC Gram-positive bacteria. In Bacillus anthracis, the spxA2 gene is highly induced in infected macrophages, which suggests an important role in the control of virulence gene expression during the anthrax disease state. We provide evidence that elevated concentrations of oxidized, active SpxA2 result from an autoregulatory positive-feedback loop driving spxA2 transcription.
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