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George NL, Bennett EC, Orlando BJ. Guarding the walls: the multifaceted roles of Bce modules in cell envelope stress sensing and antimicrobial resistance. J Bacteriol 2024; 206:e0012324. [PMID: 38869304 PMCID: PMC11270860 DOI: 10.1128/jb.00123-24] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/14/2024] Open
Abstract
Bacteria have developed diverse strategies for defending their cell envelopes from external threats. In Firmicutes, one widespread strategy is to use Bce modules-membrane protein complexes that unite a peptide-detoxifying ABC transporter with a stress response coordinating two-component system. These modules provide specific, front-line defense for a wide variety of antimicrobial peptides and small molecule antibiotics as well as coordinate responses for heat, acid, and oxidative stress. Because of these abilities, Bce modules play important roles in virulence and the development of antibiotic resistance in a variety of pathogens, including Staphylococcus, Streptococcus, and Enterococcus species. Despite their importance, Bce modules are still poorly understood, with scattered functional data in only a small number of species. In this review, we will discuss Bce module structure in light of recent cryo-electron microscopy structures of the B. subtilis BceABRS module and explore the common threads and variations-on-a-theme in Bce module mechanisms across species. We also highlight the many remaining questions about Bce module function. Understanding these multifunctional membrane complexes will enhance our understanding of bacterial stress sensing and may point toward new therapeutic targets for highly resistant pathogens.
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Affiliation(s)
- Natasha L. George
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan, USA
- Department of Microbiology, Genetics, and Immunology, Michigan State University, East Lansing, Michigan, USA
| | - Ellen C. Bennett
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan, USA
- Department of Microbiology, Genetics, and Immunology, Michigan State University, East Lansing, Michigan, USA
| | - Benjamin J. Orlando
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan, USA
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Sadaoka N, Le MNT, Kawada-Matsuo M, Eng S, Zendo T, Nakanishi J, Takeda K, Shiba H, Komatsuzawa H. Opposing genetic polymorphisms of two ABC transporters contribute to the variation of nukacin resistance in Streptococcus mutans. Appl Environ Microbiol 2024; 90:e0208423. [PMID: 38411065 PMCID: PMC10952377 DOI: 10.1128/aem.02084-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2023] [Accepted: 01/23/2024] [Indexed: 02/28/2024] Open
Abstract
Streptococcus mutans is a cariogenic bacterium that produces a variety of bacteriocins and retains resistance to these bacteriocins. In this study, we investigated the susceptibility of 127 S. mutans strains to nukacins produced by Staphylococcus spp., which are commensal bacteria in humans. We detected diverse susceptibilities among strains. Nineteen strains had a disrupted LctF (type I), which is responsible for nukacin susceptibility, whereas the remaining 108 strains had an intact LctF (type II) and displayed resistance to nukacins. However, the type I strains still showed resistance to nukacins to some extent. Interestingly, 18/19 (94.7%) type I strains carried a mukA-T locus, which is related to the synthesis of mutacin K8, and mukFEG, an ABC transporter. In contrast, among type II strains, only 6/108 strains (5.6%) had both the mukA-T locus and mukFEG, 19/108 strains (17.6%) carried only mukFEG, and 83/108 strains (76.9%) harbored neither mukA-T nor mukFEG. We also found that MukF had two variants: 305 amino acids (type α) and 302 amino acids (type β). All type I strains showed a type α (MukFα), whereas most type II strains with mukFEG (22/25 strains) had a type β (MukFβ). Then, we constructed a mukFEG-deletion mutant complemented with MukFαEG or MukFβEG and found that only MukFαEG was involved in nukacin resistance. The nukacin resistance capability of type II-LctFEG was stronger than that of MukFαEG. In conclusion, we identified a novel nukacin resistance factor, MukFEG, and either LctFEG or MukFEG was active in most strains via genetic polymorphisms depending on mukA-T genes. IMPORTANCE Streptococcus mutans is an important pathogenic bacterium not only for dental caries but also for systemic diseases. S. mutans is known to produce a variety of bacteriocins and to retain resistance these bacteriocins. In this study, two ABC transporters, LctFEG and MukFEG, were implicated in nukacin resistance and each ABC transporter has two subtypes, active and inactive. Of the two ABC transporters, only one ABC transporter was always resistant, while the other ABC transporter was inactivated by genetic mutation. Interestingly, this phenomenon was defined by the presence or absence of the mutacin K8 synthesis gene region, one of the bacteriocins of S. mutans. This suggests that the resistance acquisition is tightly controlled in each strain. This study provides important evidence that the insertion of bacteriocin synthesis genes is involved in the induction of genetic polymorphisms and suggests that bacteriocin synthesis genes may play an important role in bacterial evolution.
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Affiliation(s)
- Naoki Sadaoka
- Department of Bacteriology, Hiroshima University Graduate School of Biomedical and Health Sciences, Hiroshima, Japan
- Department of Biological Endodontics, Graduate School of Biomedical and Health Sciences, Hiroshima University, Hiroshima, Japan
| | - Mi Nguyen-Tra Le
- Department of Bacteriology, Hiroshima University Graduate School of Biomedical and Health Sciences, Hiroshima, Japan
- Project Research Centre for Oral Infectious Diseases, Hiroshima University, Hiroshima, Japan
| | - Miki Kawada-Matsuo
- Department of Bacteriology, Hiroshima University Graduate School of Biomedical and Health Sciences, Hiroshima, Japan
- Project Research Centre for Oral Infectious Diseases, Hiroshima University, Hiroshima, Japan
| | - Sopongselamuny Eng
- Department of Bacteriology, Hiroshima University Graduate School of Biomedical and Health Sciences, Hiroshima, Japan
| | - Takeshi Zendo
- Department of Bioscience and Biotechnology, Faculty of Agriculture, Graduate School, Kyushu University, Fukuoka, Japan
| | - Jun Nakanishi
- Department of Biological Endodontics, Graduate School of Biomedical and Health Sciences, Hiroshima University, Hiroshima, Japan
| | - Katsuhiro Takeda
- Department of Biological Endodontics, Graduate School of Biomedical and Health Sciences, Hiroshima University, Hiroshima, Japan
| | - Hideki Shiba
- Department of Biological Endodontics, Graduate School of Biomedical and Health Sciences, Hiroshima University, Hiroshima, Japan
| | - Hitoshi Komatsuzawa
- Department of Bacteriology, Hiroshima University Graduate School of Biomedical and Health Sciences, Hiroshima, Japan
- Project Research Centre for Oral Infectious Diseases, Hiroshima University, Hiroshima, Japan
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Li P, Yin R, Cheng J, Lin J. Bacterial Biofilm Formation on Biomaterials and Approaches to Its Treatment and Prevention. Int J Mol Sci 2023; 24:11680. [PMID: 37511440 PMCID: PMC10380251 DOI: 10.3390/ijms241411680] [Citation(s) in RCA: 11] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2023] [Revised: 07/13/2023] [Accepted: 07/17/2023] [Indexed: 07/30/2023] Open
Abstract
Bacterial biofilms can cause widespread infection. In addition to causing urinary tract infections and pulmonary infections in patients with cystic fibrosis, biofilms can help microorganisms adhere to the surfaces of various medical devices, causing biofilm-associated infections on the surfaces of biomaterials such as venous ducts, joint prostheses, mechanical heart valves, and catheters. Biofilms provide a protective barrier for bacteria and provide resistance to antimicrobial agents, which increases the morbidity and mortality of patients. This review summarizes biofilm formation processes and resistance mechanisms, as well as the main features of clinically persistent infections caused by biofilms. Considering the various infections caused by clinical medical devices, we introduce two main methods to prevent and treat biomaterial-related biofilm infection: antibacterial coatings and the surface modification of biomaterials. Antibacterial coatings depend on the covalent immobilization of antimicrobial agents on the coating surface and drug release to prevent and combat infection, while the surface modification of biomaterials affects the adhesion behavior of cells on the surfaces of implants and the subsequent biofilm formation process by altering the physical and chemical properties of the implant material surface. The advantages of each strategy in terms of their antibacterial effect, biocompatibility, limitations, and application prospects are analyzed, providing ideas and research directions for the development of novel biofilm infection strategies related to therapeutic materials.
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Affiliation(s)
| | | | | | - Jinshui Lin
- Shaanxi Key Laboratory of Chinese Jujube, College of Life Sciences, Yan’an University, Yan’an 716000, China; (P.L.); (R.Y.); (J.C.)
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Song Q, Wu H, Zhang P, Tian K, Zhu H, Qiao J. LssR plays a positive regulatory role in acid and nisin tolerance response of Lactococcus lactis. J Dairy Sci 2022; 105:6483-6498. [PMID: 35840402 DOI: 10.3168/jds.2022-21842] [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: 01/19/2022] [Accepted: 04/14/2022] [Indexed: 11/19/2022]
Abstract
In Lactococcus lactis, different regulation mechanisms can be activated to overcome the effects of adverse environmental stresses. Here, a TetR family regulator LssR was demonstrated as a positive regulator in the activation of the mechanisms involved in acid and nisin tolerance of L. lactis. The deletion of lssR led to the reduction of tolerance of L. lactis NZ9000 to nisin and acid stress, and the survival rates of NZ9000 under nisin and acid stress were roughly 20-fold, 10-fold (pH 3.0, hydrochloric acid), and 8.9-fold (pH 4.0, lactic acid) of the lssR mutant NZΔlssR, respectively. Moreover, the lssR mutant NZΔlssR also displayed a lower intracellular pH stability and a changed cell surface morphology. Subsequently, transcriptome analysis revealed that genes related to the arginine deiminase pathway, the surface polysaccharides biosynthesis, carbohydrates transport and metabolism, multidrug resistance, cell repair proteins and chaperones were predominantly down transcribed in NZΔlssR. The transcript levels of the arginine deiminase pathway and the surface polysaccharides biosynthesis-associated genes under acid and nisin stresses were compared between the wild type NZ9000 and NZΔlssR using real-time fluorescence quantitative PCR. It revealed that the arginine deiminase pathway genes (arcD1C1C2T) and the surface polysaccharides biosynthesis genes (cgT, gmhB, gmhA, hddA, tagH and tarS) were proposed to be the main regulatory mechanisms of LssR in response to the acid and nisin stresses. Overall, the important role of LssR in the acid and nisin stresses response was demonstrated and the putative regulation mechanism of LssR was revealed.
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Affiliation(s)
- Qianqian Song
- Department of Pharmaceutical Engineering, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China
| | - Hao Wu
- Department of Pharmaceutical Engineering, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China; Zhejiang Shaoxing Research Institute of Tianjin University, Shaoxing 312300, China
| | - Peng Zhang
- Department of Pharmaceutical Engineering, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China
| | - Kairen Tian
- Department of Pharmaceutical Engineering, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China
| | - Hongji Zhu
- Department of Pharmaceutical Engineering, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China.
| | - Jianjun Qiao
- Department of Pharmaceutical Engineering, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China; Zhejiang Shaoxing Research Institute of Tianjin University, Shaoxing 312300, China; Key Laboratory of Systems Bioengineering (Ministry of Education), Tianjin University, Tianjin 300072, China; SynBio Research Platform Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Tianjin 300072, China.
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Costa M, Meirinhos C, Cunha E, Gomes D, Pereira M, Dias R, Tavares L, Oliveira M. Nisin Mutant Prevention Concentration and the Role of Subinhibitory Concentrations on Resistance Development by Diabetic Foot Staphylococci. Antibiotics (Basel) 2022; 11:antibiotics11070972. [PMID: 35884226 PMCID: PMC9311964 DOI: 10.3390/antibiotics11070972] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2022] [Revised: 07/14/2022] [Accepted: 07/15/2022] [Indexed: 12/10/2022] Open
Abstract
The most prevalent microorganism in diabetic foot infections (DFI) is Staphylococcus aureus, an important multidrug-resistant pathogen. The antimicrobial peptide nisin is a promising compound for DFI treatment, being effective against S. aureus. However, to avoid the selection of resistant mutants, correct drug therapeutic doses must be established, being also important to understand if nisin subinhibitory concentrations (subMIC) can potentiate resistant genes transfer between clinical isolates or mutations in genes associated with nisin resistance. The mutant selection window (MSW) of nisin was determined for 23 DFI S. aureus isolates; a protocol aiming to prompt vanA horizontal transfer between enterococci to clinical S. aureus was performed; and nisin subMIC effect on resistance evolution was assessed through whole-genome sequencing (WGS) applied to isolates subjected to a MEGA-plate assay. MSW ranged from 5–360 μg/mL for two isolates, from 5–540 μg/mL for three isolates, and from 5–720 μg/mL for one isolate. In the presence of nisin subMIC values, no transconjugants were obtained, indicating that nisin does not seem to promote vanA transfer. Finally, WGS analysis showed that incubation in the presence of nisin subMIC did not promote the occurrence of significant mutations in genes related to nisin resistance, supporting nisin application to DFI treatment.
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Affiliation(s)
- Margarida Costa
- CIISA—Centro de Investigação Interdisciplinar em Sanidade Animal, Faculdade de Medicina Veterinária, Universidade de Lisboa, Av. da Universidade Técnica de Lisboa, 1300-477 Lisboa, Portugal; (M.C.); (C.M.); (D.G.); (L.T.); (M.O.)
- Laboratório Associado para Ciência Animal e Veterinária (AL4AnimalS), 1300-477 Lisbon, Portugal
| | - Cláudia Meirinhos
- CIISA—Centro de Investigação Interdisciplinar em Sanidade Animal, Faculdade de Medicina Veterinária, Universidade de Lisboa, Av. da Universidade Técnica de Lisboa, 1300-477 Lisboa, Portugal; (M.C.); (C.M.); (D.G.); (L.T.); (M.O.)
- Laboratório Associado para Ciência Animal e Veterinária (AL4AnimalS), 1300-477 Lisbon, Portugal
| | - Eva Cunha
- CIISA—Centro de Investigação Interdisciplinar em Sanidade Animal, Faculdade de Medicina Veterinária, Universidade de Lisboa, Av. da Universidade Técnica de Lisboa, 1300-477 Lisboa, Portugal; (M.C.); (C.M.); (D.G.); (L.T.); (M.O.)
- Laboratório Associado para Ciência Animal e Veterinária (AL4AnimalS), 1300-477 Lisbon, Portugal
- Correspondence:
| | - Diana Gomes
- CIISA—Centro de Investigação Interdisciplinar em Sanidade Animal, Faculdade de Medicina Veterinária, Universidade de Lisboa, Av. da Universidade Técnica de Lisboa, 1300-477 Lisboa, Portugal; (M.C.); (C.M.); (D.G.); (L.T.); (M.O.)
- Laboratório Associado para Ciência Animal e Veterinária (AL4AnimalS), 1300-477 Lisbon, Portugal
| | - Marcelo Pereira
- Biosystems and Integrative Sciences Institute, Faculdade de Ciências, Universidade de Lisboa, Campo Grande, 1749-016 Lisboa, Portugal; (M.P.); (R.D.)
| | - Ricardo Dias
- Biosystems and Integrative Sciences Institute, Faculdade de Ciências, Universidade de Lisboa, Campo Grande, 1749-016 Lisboa, Portugal; (M.P.); (R.D.)
| | - Luís Tavares
- CIISA—Centro de Investigação Interdisciplinar em Sanidade Animal, Faculdade de Medicina Veterinária, Universidade de Lisboa, Av. da Universidade Técnica de Lisboa, 1300-477 Lisboa, Portugal; (M.C.); (C.M.); (D.G.); (L.T.); (M.O.)
- Laboratório Associado para Ciência Animal e Veterinária (AL4AnimalS), 1300-477 Lisbon, Portugal
| | - Manuela Oliveira
- CIISA—Centro de Investigação Interdisciplinar em Sanidade Animal, Faculdade de Medicina Veterinária, Universidade de Lisboa, Av. da Universidade Técnica de Lisboa, 1300-477 Lisboa, Portugal; (M.C.); (C.M.); (D.G.); (L.T.); (M.O.)
- Laboratório Associado para Ciência Animal e Veterinária (AL4AnimalS), 1300-477 Lisbon, Portugal
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Le MNT, Kawada-Matsuo M, Komatsuzawa H. Efficiency of Antimicrobial Peptides Against Multidrug-Resistant Staphylococcal Pathogens. Front Microbiol 2022; 13:930629. [PMID: 35756032 PMCID: PMC9218695 DOI: 10.3389/fmicb.2022.930629] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2022] [Accepted: 05/18/2022] [Indexed: 11/13/2022] Open
Abstract
Antibiotics play a vital role in saving millions of lives from fatal infections; however, the inappropriate use of antibiotics has led to the emergence and propagation of drug resistance worldwide. Multidrug-resistant bacteria represent a significant challenge to treating infections due to the limitation of available antibiotics, necessitating the investigation of alternative treatments for combating these superbugs. Under such circumstances, antimicrobial peptides (AMPs), including human-derived AMPs and bacteria-derived AMPs (so-called bacteriocins), are considered potential therapeutic drugs owing to their high efficacy against infectious bacteria and the poor ability of these microorganisms to develop resistance to them. Several staphylococcal species including Staphylococcus aureus, Staphylococcus epidermidis, Staphylococcus haemolyticus, and Staphylococcus saprophyticus are commensal bacteria and known to cause many opportunistic infectious diseases. Methicillin-resistant Staphylococci, especially methicillin-resistant S. aureus (MRSA), are of particular concern among the critical multidrug-resistant infectious Gram-positive pathogens. Within the past decade, studies have reported promising AMPs that are effective against MRSA and other methicillin-resistant Staphylococci. This review discusses the sources and mechanisms of AMPs against staphylococcal species, as well as their potential to become chemotherapies for clinical infections caused by multidrug-resistant staphylococci.
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Affiliation(s)
- Mi Nguyen-Tra Le
- Department of Bacteriology, Graduate School of Biomedical and Health Sciences, Hiroshima University, Hiroshima, Japan
| | - Miki Kawada-Matsuo
- Department of Bacteriology, Graduate School of Biomedical and Health Sciences, Hiroshima University, Hiroshima, Japan
| | - Hitoshi Komatsuzawa
- Department of Bacteriology, Graduate School of Biomedical and Health Sciences, Hiroshima University, Hiroshima, Japan
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Weixler D, Berghoff M, Ovchinnikov KV, Reich S, Goldbeck O, Seibold GM, Wittmann C, Bar NS, Eikmanns BJ, Diep DB, Riedel CU. Recombinant production of the lantibiotic nisin using Corynebacterium glutamicum in a two-step process. Microb Cell Fact 2022; 21:11. [PMID: 35033086 PMCID: PMC8760817 DOI: 10.1186/s12934-022-01739-y] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2021] [Accepted: 01/03/2022] [Indexed: 12/22/2022] Open
Abstract
BACKGROUND The bacteriocin nisin is naturally produced by Lactococcus lactis as an inactive prepeptide that is modified posttranslationally resulting in five (methyl-)lanthionine rings characteristic for class Ia bacteriocins. Export and proteolytic cleavage of the leader peptide results in release of active nisin. By targeting the universal peptidoglycan precursor lipid II, nisin has a broad target spectrum including important human pathogens such as Listeria monocytogenes and methicillin-resistant Staphylococcus aureus strains. Industrial nisin production is currently performed using natural producer strains resulting in rather low product purity and limiting its application to preservation of dairy food products. RESULTS We established heterologous nisin production using the biotechnological workhorse organism Corynebacterium glutamicum in a two-step process. We demonstrate successful biosynthesis and export of fully modified prenisin and its activation to mature nisin by a purified, soluble variant of the nisin protease NisP (sNisP) produced in Escherichia coli. Active nisin was detected by a L. lactis sensor strain with strictly nisin-dependent expression of the fluorescent protein mCherry. Following activation by sNisP, supernatants of the recombinant C. glutamicum producer strain cultivated in standard batch fermentations contained at least 1.25 mg/l active nisin. CONCLUSIONS We demonstrate successful implementation of a two-step process for recombinant production of active nisin with C. glutamicum. This extends the spectrum of bioactive compounds that may be produced using C. glutamicum to a bacteriocin harboring complex posttranslational modifications. Our results provide a basis for further studies to optimize product yields, transfer production to sustainable substrates and purification of pharmaceutical grade nisin.
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Affiliation(s)
- Dominik Weixler
- Institute of Microbiology and Biotechnology, University of Ulm, Albert-Einstein-Allee 11, 89081, Ulm, Germany
| | - Max Berghoff
- Institute of Microbiology and Biotechnology, University of Ulm, Albert-Einstein-Allee 11, 89081, Ulm, Germany
| | - Kirill V Ovchinnikov
- Faculty of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences, Ås, Norway
| | - Sebastian Reich
- Institute of Microbiology and Biotechnology, University of Ulm, Albert-Einstein-Allee 11, 89081, Ulm, Germany
| | - Oliver Goldbeck
- Institute of Microbiology and Biotechnology, University of Ulm, Albert-Einstein-Allee 11, 89081, Ulm, Germany
| | - Gerd M Seibold
- Institute of Microbiology and Biotechnology, University of Ulm, Albert-Einstein-Allee 11, 89081, Ulm, Germany
- Department of Biotechnology and Biomedicine, Technical University of Denmark, Lyngby, Denmark
| | - Christoph Wittmann
- Institute of Systems Biotechnology, Saarland University, Saarbrücken, Germany
| | - Nadav S Bar
- Department of Chemical Engineering, Norwegian University of Science and Technology, Trondheim, Norway
| | - Bernhard J Eikmanns
- Institute of Microbiology and Biotechnology, University of Ulm, Albert-Einstein-Allee 11, 89081, Ulm, Germany
| | - Dzung B Diep
- Faculty of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences, Ås, Norway
| | - Christian U Riedel
- Institute of Microbiology and Biotechnology, University of Ulm, Albert-Einstein-Allee 11, 89081, Ulm, Germany.
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Bleul L, Francois P, Wolz C. Two-Component Systems of S. aureus: Signaling and Sensing Mechanisms. Genes (Basel) 2021; 13:34. [PMID: 35052374 PMCID: PMC8774646 DOI: 10.3390/genes13010034] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2021] [Revised: 12/21/2021] [Accepted: 12/22/2021] [Indexed: 12/18/2022] Open
Abstract
Staphylococcus aureus encodes 16 two-component systems (TCSs) that enable the bacteria to sense and respond to changing environmental conditions. Considering the function of these TCSs in bacterial survival and their potential role as drug targets, it is important to understand the exact mechanisms underlying signal perception. The differences between the sensing of appropriate signals and the transcriptional activation of the TCS system are often not well described, and the signaling mechanisms are only partially understood. Here, we review present insights into which signals are sensed by histidine kinases in S. aureus to promote appropriate gene expression in response to diverse environmental challenges.
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Affiliation(s)
- Lisa Bleul
- Interfaculty Institute of Microbiology and Infection Medicine, University of Tübingen, 72076 Tubingen, Germany;
- Cluster of Excellence EXC 2124 “Controlling Microbes to Fight Infections”, University of Tübingen, Elfriede-Aulhorn-Str. 6, 72076 Tubingen, Germany
| | - Patrice Francois
- Genomic Research Laboratory, Infectious Diseases Service, University Hospitals of Geneva University Medical Center, Michel Servet 1, CH-1211 Geneva, Switzerland;
| | - Christiane Wolz
- Interfaculty Institute of Microbiology and Infection Medicine, University of Tübingen, 72076 Tubingen, Germany;
- Cluster of Excellence EXC 2124 “Controlling Microbes to Fight Infections”, University of Tübingen, Elfriede-Aulhorn-Str. 6, 72076 Tubingen, Germany
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Lactococcus lactis Resistance to Aureocin A53- and Enterocin L50-Like Bacteriocins and Membrane-Targeting Peptide Antibiotics Relies on the YsaCB-KinG-LlrG Four-Component System. Antimicrob Agents Chemother 2021; 65:e0092121. [PMID: 34516250 DOI: 10.1128/aac.00921-21] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Resistance to nonribosomally synthesized peptide antibiotics affecting the cell envelope is well studied and mostly associated with the action of peptide-sensing and detoxification (PSD) modules, which consist of a two-component system (TCS) and an ATP-binding cassette (ABC) transporter. In contrast, the mechanisms of resistance to ribosomally synthesized bacterial toxic peptides (bacteriocins), which also affect the cell envelope, are studied to a lesser extent, and the possible cross-resistance between them and antibiotics is still poorly understood. In the present study, we investigated the development of resistance of Lactococcus lactis to aureocin A53- and enterocin L50-like bacteriocins and cross-resistance with antibiotics. First, 19 spontaneous mutants resistant to their representatives were selected and also displayed changes in sensitivity to peptide antibiotics acting on the cell envelope (bacitracin, daptomycin, and gramicidin). Sequencing of their genomes revealed mutations in genes encoding the ABC transporter YsaCB and the TCS KinG-LlrG, the emergence of which induced the upregulation of the dltABCD and ysaDCB operons. The ysaB mutations were either nonsense or frameshift mutations and led to the generation of truncated YsaB but with the conserved N-terminal FtsX domain intact. Deletions of ysaCB or llrG had a minor effect on the resistance of the obtained mutants to the tested bacteriocins, daptomycin, and gramicidin, indicating that the development of resistance is dependent on the modification of the protein rather than its absence. In further corroboration of the above-mentioned conclusion, we show that the FtsX domain, which functions effectively when YsaB is lacking its central and C-terminal parts, is critical for resistance to these antimicrobials.
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Kawada-Matsuo M, Le MNT, Komatsuzawa H. Antibacterial Peptides Resistance in Staphylococcus aureus: Various Mechanisms and the Association with Pathogenicity. Genes (Basel) 2021; 12:genes12101527. [PMID: 34680923 PMCID: PMC8535901 DOI: 10.3390/genes12101527] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2021] [Revised: 09/21/2021] [Accepted: 09/23/2021] [Indexed: 01/15/2023] Open
Abstract
Staphylococcus aureus is a bacterium that mainly colonizes the nasal cavity and skin. To colonize the host, it is necessary for S. aureus to resist many antibacterial factors derived from human and commensal bacteria. Among them are the bacteria-derived antimicrobial peptides (AMPs) called bacteriocins. It was reported that some two-component systems (TCSs), which are signal transduction systems specific to bacteria, are involved in the resistance to several bacteriocins in S. aureus. However, the TCS-mediated resistance is limited to relatively low concentrations of bacteriocins, while high concentrations of bacteriocins still exhibit antibacterial activity against S. aureus. To determine whether we could obtain highly bacteriocin-resistant mutants, we tried to isolate highly nisin A-resistant mutants by exposing the cells to sub-minimum inhibitory concentrations (MICs) of nisin A. Nisin A is one of the bacteriocins produced by Lactococcus lactis and is utilized as a food preservative worldwide. Finally, we obtained highly nisin A-resistant mutants with mutations in one TCS, BraRS, and in PmtR, which is involved in the expression of pmtABCD. Notably, some highly resistant strains also showed increased pathogenicity. Based on our findings, this review provides up-to-date information on the role of TCSs in the susceptibility to antibacterial peptides. Additionally, the mechanism for high antimicrobial peptides resistance and its association with pathogenicity in S. aureus is elucidated.
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Liu J, Chen F, Wang X, Peng H, Zhang H, Wang KJ. The Synergistic Effect of Mud Crab Antimicrobial Peptides Sphistin and Sph 12-38 With Antibiotics Azithromycin and Rifampicin Enhances Bactericidal Activity Against Pseudomonas Aeruginosa. Front Cell Infect Microbiol 2020; 10:572849. [PMID: 33194811 PMCID: PMC7645104 DOI: 10.3389/fcimb.2020.572849] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2020] [Accepted: 09/02/2020] [Indexed: 12/16/2022] Open
Abstract
Overuse or abuse of antibiotics has undoubtedly accelerated the increasing prevalence of global antibiotic resistance crisis, and thus, people have been trying to explore approaches to decrease dosage of antibiotics or find new antibacterial agents for many years. Antimicrobial peptides (AMPs) are the ideal candidates that could kill pathogens and multidrug-resistant bacteria either alone or in combination with conventional antibiotics. In the study, the antimicrobial efficacy of mud crab Scylla paramamosain AMPs Sphistin and Sph12−38 in combination with eight selected antibiotics was evaluated using a clinical pathogen, Pseudomonas aeruginosa. It was interesting to note that the in vitro combination of rifampicin and azithromycin with Sphistin and Sph12−38 showed significant synergistic activity against P. aeruginosa. Moreover, an in vivo study was carried out using a mouse model challenged with P. aeruginosa, and the result showed that the combination of Sph12−38 with either rifampicin or azithromycin could significantly promote the healing of wounds and had the healing time shortened to 4–5 days compared with 7–8 days in control. The underlying mechanism might be due to the binding of Sphistin and Sph12−38 with P. aeruginosa lipopolysaccharides (LPS) and subsequent promotion of the intracellular uptake of rifampicin and azithromycin. Taken together, the significant synergistic antibacterial effect on P. aeruginosa in vitro and in vivo conferred by the combination of low dose of Sphistin and Sph12−38 with low dose of rifampicin and azithromycin would be beneficial for the control of antibiotic resistance and effective treatment of P. aeruginosa-infected diseases in the future.
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Affiliation(s)
- Jie Liu
- State Key Laboratory of Marine Environmental Science, College of Ocean & Earth Sciences, Xiamen University, Xiamen, China
| | - Fangyi Chen
- State Key Laboratory of Marine Environmental Science, College of Ocean & Earth Sciences, Xiamen University, Xiamen, China.,State-Province Joint Engineering Laboratory of Marine Bioproducts and Technology, College of Ocean & Earth Sciences, Xiamen University, Xiamen, China
| | - Xiaofei Wang
- State Key Laboratory of Marine Environmental Science, College of Ocean & Earth Sciences, Xiamen University, Xiamen, China
| | - Hui Peng
- State Key Laboratory of Marine Environmental Science, College of Ocean & Earth Sciences, Xiamen University, Xiamen, China.,State-Province Joint Engineering Laboratory of Marine Bioproducts and Technology, College of Ocean & Earth Sciences, Xiamen University, Xiamen, China
| | - Hua Zhang
- State Key Laboratory of Marine Environmental Science, College of Ocean & Earth Sciences, Xiamen University, Xiamen, China
| | - Ke-Jian Wang
- State Key Laboratory of Marine Environmental Science, College of Ocean & Earth Sciences, Xiamen University, Xiamen, China.,State-Province Joint Engineering Laboratory of Marine Bioproducts and Technology, College of Ocean & Earth Sciences, Xiamen University, Xiamen, China
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12
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Campelo AB, López-González MJ, Escobedo S, Janzen T, Neves AR, Rodríguez A, Martínez B. Mutations Selected After Exposure to Bacteriocin Lcn972 Activate a Bce-Like Bacitracin Resistance Module in Lactococcus lactis. Front Microbiol 2020; 11:1805. [PMID: 32903467 PMCID: PMC7438565 DOI: 10.3389/fmicb.2020.01805] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2020] [Accepted: 07/09/2020] [Indexed: 12/20/2022] Open
Abstract
Resistance against antimicrobial peptides (AMPs) is often mediated by detoxification modules that rely on sensing the AMP through a BceAB-like ATP-binding cassette (ABC) transporter that subsequently activates a cognate two-component system (TCS) to mount the cell response. Here, the Lactococcus lactis ABC transporter YsaDCB is shown to constitute, together with TCS-G, a detoxification module that protects L. lactis against bacitracin and the bacteriocin Lcn972, both AMPs that inhibit cell wall biosynthesis. Initially, increased expression of ysaDCB was detected by RT-qPCR in three L. lactis resistant to Lcn972, two of which were also resistant to bacitracin. These mutants shared, among others, single-point mutations in ysaB coding for the putative Bce-like permease. These results led us to investigate the function of YsaDCB ABC-transporter and study the impact of these mutations. Expression in trans of ysaDCB in L. lactis NZ9000, a strain that lacks a functional detoxification module, enhanced resistance to both AMPs, demonstrating its role as a resistance factor in L. lactis. When the three different ysaB alleles from the mutants were expressed, all of them outperformed the wild-type transporter in resistance against Lcn972 but not against bacitracin, suggesting a distinct mode of protection against each AMP. Moreover, P ysaD promoter fusions, designed to measure the activation of the detoxification module, revealed that the ysaB mutations unlock transcriptional control by TCS-G, resulting in constitutive expression of the ysaDCB operon. Finally, deletion of ysaD was also performed to get an insight into the function of this gene. ysaD encodes a secreted peptide and is part of the ysaDCB operon. YsaD appears to modulate signal relay between the ABC transporter and TCS-G, based on the different response of the P ysaD promoter fusions when it is not present. Altogether, the results underscore the unique features of this lactococcal detoxification module that warrant further research to advance in our overall understanding of these important resistance factors in bacteria.
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Affiliation(s)
- Ana Belén Campelo
- DairySafe group, Department of Technology and Biotechnology of Dairy Products, Instituto de Productos Lácteos de Asturias (IPLA), Consejo Superior de Investigaciones Científicas (CSIC), Villaviciosa, Spain
| | - María Jesús López-González
- DairySafe group, Department of Technology and Biotechnology of Dairy Products, Instituto de Productos Lácteos de Asturias (IPLA), Consejo Superior de Investigaciones Científicas (CSIC), Villaviciosa, Spain.,Instituto de Investigación Sanitaria del Principado de Asturias (ISPA), Oviedo, Spain
| | - Susana Escobedo
- DairySafe group, Department of Technology and Biotechnology of Dairy Products, Instituto de Productos Lácteos de Asturias (IPLA), Consejo Superior de Investigaciones Científicas (CSIC), Villaviciosa, Spain.,Instituto de Investigación Sanitaria del Principado de Asturias (ISPA), Oviedo, Spain
| | | | | | - Ana Rodríguez
- DairySafe group, Department of Technology and Biotechnology of Dairy Products, Instituto de Productos Lácteos de Asturias (IPLA), Consejo Superior de Investigaciones Científicas (CSIC), Villaviciosa, Spain.,Instituto de Investigación Sanitaria del Principado de Asturias (ISPA), Oviedo, Spain
| | - Beatriz Martínez
- DairySafe group, Department of Technology and Biotechnology of Dairy Products, Instituto de Productos Lácteos de Asturias (IPLA), Consejo Superior de Investigaciones Científicas (CSIC), Villaviciosa, Spain.,Instituto de Investigación Sanitaria del Principado de Asturias (ISPA), Oviedo, Spain
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13
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Gil-Gil T, Laborda P, Sanz-García F, Hernando-Amado S, Blanco P, Martínez JL. Antimicrobial resistance: A multifaceted problem with multipronged solutions. Microbiologyopen 2020; 8:e945. [PMID: 31724836 PMCID: PMC6855134 DOI: 10.1002/mbo3.945] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2019] [Accepted: 09/19/2019] [Indexed: 12/12/2022] Open
Abstract
Infectious diseases still stand as a major cause of morbidity and mortality, and this problem can be worsened with the current antimicrobial resistance crisis. To tackle this crisis more studies analyzing the causes, routes, and reservoirs where antimicrobial resistance can emerge and expand, together with new antimicrobials and strategies for fighting antimicrobial resistance are needed. In the current special issue of MicrobiologyOpen, a set of articles dealing with the multiple faces of antimicrobial resistance are presented. These articles provide new information for understanding and addressing this problem.
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Affiliation(s)
| | - Pablo Laborda
- Centro Nacional de Biotecnología CSIC, Madrid, Spain
| | | | | | - Paula Blanco
- Centro Nacional de Biotecnología CSIC, Madrid, Spain
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14
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Staphylococcus aureus Virulence Affected by an Alternative Nisin A Resistance Mechanism. Appl Environ Microbiol 2020; 86:AEM.02923-19. [PMID: 32086306 DOI: 10.1128/aem.02923-19] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2019] [Accepted: 02/04/2020] [Indexed: 01/25/2023] Open
Abstract
Nisin A is a bacteriocin produced by Lactococcus lactis and is widely used as a food preservative. Staphylococcus aureus has the BraRS-VraDE system that provides resistance against low concentrations of nisin A. BraRS is a two-component system that induces the expression of the ABC transporter VraDE. Previously, we isolated a highly nisin A-resistant strain with increased VraDE expression due to a mutation in braRS In this study, we isolated S. aureus MW2 mutants with BraRS-VraDE-independent nisin A resistance. These mutants, designated SAN2 ( S. aureus nisin resistant) and SAN469, had a mutation in pmtR, which encodes a transcriptional regulator responsible for the expression of the pmtABCD operon. As a result, these mutants exhibited increased expression of PmtABCD, a transporter responsible for the export of phenol-soluble modulin (PSM). Characterization of the mutants revealed that they have decreased susceptibility to human β-defensin-3 (hBD3) and LL37, which are innate immune factors. Additionally, these mutants showed higher hemolytic activity than the original MW2 strain. Furthermore, in a mouse bacteremia model, the SAN2 strain exhibited a lower survival rate than the original MW2 strain. These results indicate that the increased expression of pmtABCD due to a pmtR mutation is an alternative nisin A resistance mechanism that also affects virulence in S. aureus IMPORTANCE Recently, the emergence of antibiotic-resistant bacteria has resulted in serious problems for chemotherapy. In addition, many antibacterial agents, such as disinfectants and food additives, are widely used. Therefore, there is a possibility that bacteria are becoming resistant to some antibacterial agents. In this study, we investigated whether Staphylococcus aureus can become resistant to nisin A, one of the bacteriocins applied as a food additive. We isolated a highly nisin A-resistant strain designated SAN2 that displayed increased expression of Pmt proteins, which are involved in the secretion of virulence factors called phenol-soluble modulins (PSMs). This strain also showed decreased susceptibility to human antimicrobial peptides and increased hemolytic activity. In addition, SAN2 showed increased lethal activity in a mouse bacteremia model. Our study provides new insights into the possibility that the acquisition of resistance against food preservatives may modulate virulence in S. aureus, suggesting that we need to pay more attention to the use of food preservatives together with antibiotics.
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15
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El Shazely B, Yu G, Johnston PR, Rolff J. Resistance Evolution Against Antimicrobial Peptides in Staphylococcus aureus Alters Pharmacodynamics Beyond the MIC. Front Microbiol 2020; 11:103. [PMID: 32117132 PMCID: PMC7033599 DOI: 10.3389/fmicb.2020.00103] [Citation(s) in RCA: 49] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2019] [Accepted: 01/17/2020] [Indexed: 12/03/2022] Open
Abstract
Antimicrobial peptides (AMPs) have been proposed as a promising class of new antimicrobials partly because they are less susceptible to bacterial resistance evolution. This is possibly caused by their mode of action but also by their pharmacodynamic characteristics, which differ significantly from conventional antibiotics. Although pharmacodynamics of antibiotic resistant strains have been studied, such data are lacking for AMP resistant strains. Here, we investigated if the pharmacodynamics of the Gram-positive human pathogen Staphylococcous aureus evolve under antimicrobial peptide selection. Interestingly, the Hill coefficient (kappa κ) evolves together with the minimum inhibition concentration (MIC). Except for one genotype, strains harboring mutations in menF and atl, all mutants had higher kappa than the non-selected sensitive controls. Higher κ results in steeper pharmacodynamic curve and, importantly, in a narrower mutant selection window. S. aureus selected for resistance to melittin displayed cross resistant against pexiganan and had as steep pharmacodynamic curves (high κ) as pexiganan-selected lines. By contrast, the pexiganan-sensitive tenecin-selected lines displayed lower κ. Taken together, our data demonstrate that pharmacodynamic parameters are not fixed traits of particular drug/strain interactions but actually evolve under drug treatment. The contribution of factors such as κ and the maximum and minimum growth rates on the dynamics and probability of resistance evolution are open questions that require urgent attention.
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Affiliation(s)
- Baydaa El Shazely
- Evolutionary Biology, Institute for Biology, Free University of Berlin, Berlin, Germany.,Zoology Department, Faculty of Science, Alexandria University, Alexandria, Egypt
| | - Guozhi Yu
- College of Life Sciences, Sichuan Agricultural University, Ya'an, China
| | - Paul R Johnston
- Evolutionary Biology, Institute for Biology, Free University of Berlin, Berlin, Germany.,Berlin Center for Genomics in Biodiversity Research, Berlin, Germany.,Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB), Berlin, Germany
| | - Jens Rolff
- Evolutionary Biology, Institute for Biology, Free University of Berlin, Berlin, Germany.,Berlin Center for Genomics in Biodiversity Research, Berlin, Germany.,Berlin-Brandenburg Institute of Advanced Biodiversity Research, Berlin, Germany
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16
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El Shazely B, Urbański A, Johnston PR, Rolff J. In vivo exposure of insect AMP resistant Staphylococcus aureus to an insect immune system. INSECT BIOCHEMISTRY AND MOLECULAR BIOLOGY 2019; 110:60-68. [PMID: 31051236 DOI: 10.1016/j.ibmb.2019.04.017] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/01/2019] [Revised: 04/04/2019] [Accepted: 04/29/2019] [Indexed: 06/09/2023]
Abstract
Antimicrobial peptides (AMPs) are important immune effectors in insects. Bacteria have a limited number of ways to resist AMPs, and AMP-resistance is often costly. Recently, it has become clear that AMP activities in vitro and in vivo differ. Although some studies have followed the in vivo survival of AMP resistant pathogens, studying a pathogen resistant to the AMPs of that particular host has never been reported. Here, we infected the mealworm beetle Tenebrio molitor with Staphylococcus aureus strains that were evolved in vitro in the presence of one or two antimicrobial peptides from T. molitor. We found that the Tenebrio immune system could clear mutant Tenecin resistant strains at least as efficiently as sensitive controls. The bacterial load of Tenecin resistant S. aureus segregated by mutation. Strains with mutations in both the pmt and rpo operons showed the highest in vivo survival and therefore showed the lowest fitness cost amongst the evolved resistance mutations. In contrast, Tenecin resistant strains with mutations in the nsa and rpo operons showed much lower survival within the hosts. Our study shows that Tenecin resistant strains are phagocytosed at a lower rate. The nsa/rpo mutants were phagocytosed at a higher rate than other Tenecin resistant S. aureus strains. The differences in resistance against AMPs and phagocytosis did not translate into changes in virulence. AMP resistance, while a prerequisite for an infection in vertebrates, does not provide a survival advantage to S. aureus in a host environment that is dominated by AMPs.
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Affiliation(s)
- Baydaa El Shazely
- Evolutionary Biology, Institute for Biology, Free University of Berlin, Berlin, Germany; Zoology Department, Faculty of Science, Alexandria University, Alexandria, Egypt
| | - Arkadiusz Urbański
- Department of Animal Physiology and Development, Faculty of Biology, Adam Mickiewicz University in Poznań, Poland
| | - Paul R Johnston
- Evolutionary Biology, Institute for Biology, Free University of Berlin, Berlin, Germany; Berlin Center for Genomics in Biodiversity Research, Berlin, Germany; Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB), Berlin, Germany
| | - Jens Rolff
- Evolutionary Biology, Institute for Biology, Free University of Berlin, Berlin, Germany; Berlin Center for Genomics in Biodiversity Research, Berlin, Germany; Berlin-Brandenburg Institute of Advanced Biodiversity Research (BBIB), Berlin, Germany.
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17
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Arii K, Kawada‐Matsuo M, Oogai Y, Noguchi K, Komatsuzawa H. Single mutations in BraRS confer high resistance against nisin A in Staphylococcus aureus. Microbiologyopen 2019; 8:e791. [PMID: 30656859 PMCID: PMC6854852 DOI: 10.1002/mbo3.791] [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: 09/11/2018] [Revised: 12/03/2018] [Accepted: 12/03/2018] [Indexed: 01/09/2023] Open
Abstract
Nisin A is a lantibiotic produced by Lactococcus lactis that is widely used as a food preservative. In Staphylococcus aureus, the BraRS two‐component system (TCS) senses nisin A and regulates the expression of the ABC transporter VraDE, which is responsible for nisin A resistance. In this study, we exposed S. aureus to a sub‐minimum inhibition concentration of nisin A and obtained three spontaneous mutants that were highly resistant to this lantibiotic, designated as SAN (S. aureus nisin resistant) 1, SAN8, and SAN87. In the wild‐type S. aureus strain, VraDE expression was induced by nisin A. In contrast, SAN8 and SAN87 showed constitutively high VraDE expression, even in the absence of nisin A, while SAN1 showed higher BraRS expression, which resulted in high VraDE expression in the presence of nisin A. We identified a single mutation in the promoter region of braXRS in SAN1, whereas SAN8 and SAN87 had single mutations in braR and braS, respectively. Interestingly, even the unphosphorylated form of the mutant BraR protein induced VraDE expression. These results indicate that conformational changes in BraS or BraR resulting from the point mutations may result in the constitutive expression of VraDE, allowing S. aureus to adapt to high concentrations of nisin A.
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Affiliation(s)
- Kaoru Arii
- Department of Oral MicrobiologyKagoshima University Graduate School of Medical and Dental SciencesKagoshimaJapan
- Department of PeriodontologyKagoshima University Graduate School of Medical and Dental SciencesKagoshimaJapan
| | - Miki Kawada‐Matsuo
- Department of Oral MicrobiologyKagoshima University Graduate School of Medical and Dental SciencesKagoshimaJapan
| | - Yuichi Oogai
- Department of Oral MicrobiologyKagoshima University Graduate School of Medical and Dental SciencesKagoshimaJapan
| | - Kazuyuki Noguchi
- Department of PeriodontologyKagoshima University Graduate School of Medical and Dental SciencesKagoshimaJapan
| | - Hitoshi Komatsuzawa
- Department of Oral MicrobiologyKagoshima University Graduate School of Medical and Dental SciencesKagoshimaJapan
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