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Majdi C, Meffre P, Benfodda Z. Recent advances in the development of bacterial response regulators inhibitors as antibacterial and/or antibiotic adjuvant agent: A new approach to combat bacterial resistance. Bioorg Chem 2024; 150:107606. [PMID: 38968903 DOI: 10.1016/j.bioorg.2024.107606] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2024] [Revised: 06/21/2024] [Accepted: 06/28/2024] [Indexed: 07/07/2024]
Abstract
The number of new antibacterial agents currently being discovered is insufficient to combat bacterial resistance. It is extremely challenging to find new antibiotics and to introduce them to the pharmaceutical market. Therefore, special attention must be given to find new strategies to combat bacterial resistance and prevent bacteria from developing resistance. Two-component system is a transduction system and the most prevalent mechanism employed by bacteria to respond to environmental changes. This signaling system consists of a membrane sensor histidine kinase that perceives environmental stimuli and a response regulator which acts as a transcription factor. The approach consisting of developing response regulators inhibitors with antibacterial activity or antibiotic adjuvant activity is a novel approach that has never been previously reviewed. In this review we report for the first time, the importance of targeting response regulators and summarizing all existing studies carried out from 2008 until now on response regulators inhibitors as antibacterial agents or / and antibiotic adjuvants. Moreover, we describe the antibacterial activity and/or antibiotic adjuvants activity against the studied bacterial strains and the mechanism of different response regulator inhibitors when it's possible.
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2
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Gaddy KE, Bensch EM, Cavanagh J, Milton ME. Insights into DNA-binding motifs and mechanisms of Francisella tularensis novicida two-component system response regulator proteins QseB, KdpE, and BfpR. Biochem Biophys Res Commun 2024; 722:150150. [PMID: 38805787 DOI: 10.1016/j.bbrc.2024.150150] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2024] [Revised: 05/09/2024] [Accepted: 05/20/2024] [Indexed: 05/30/2024]
Abstract
Two component system bacterial response regulators are typically DNA-binding proteins which enable the genetic regulation of many adaptive bacterial behaviors. Despite structural similarity across response regulator families, there is a diverse array of DNA-binding mechanisms. Bacteria usually encode several dozen two-component system response regulators, but Francisella tularensis only encodes three. Due to their simplified response regulatory network, Francisella species are a model for studying the role of response regulator proteins in virulence. Here, we show that Francisella response regulators QseB, KdpE, and BfpR all utilize different DNA-binding mechanisms. Our evidence suggests that QseB follows a simple mechanism whereby it binds a single inverted repeat sequence with a higher affinity upon phosphorylation. This behavior is independent of whether QseB is a positive or negative regulator of the gene as demonstrated by qseB and priM promoter sequences, respectively. Similarly, KdpE binds DNA more tightly upon phosphorylation, but also exhibits a cooperative binding isotherm. While we propose a KdpE binding site, it is possible that KdpE has a complex DNA-binding mechanism potentially involving multiple copies of KdpE being recruited to a promoter region. Finally, we show that BfpR appears to bind a region of its own promoter sequence with a lower affinity upon phosphorylation. Further structural and enzymatic work will need to be performed to deconvolute the KdpE and BfpR binding mechanisms.
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Affiliation(s)
- Keegan E Gaddy
- Department of Biochemistry and Molecular Biology, Brody School of Medicine, East Carolina University, Greenville, NC, USA
| | - Elody M Bensch
- Department of Biochemistry and Molecular Biology, Brody School of Medicine, East Carolina University, Greenville, NC, USA
| | - John Cavanagh
- Department of Biochemistry and Molecular Biology, Brody School of Medicine, East Carolina University, Greenville, NC, USA
| | - Morgan E Milton
- Department of Biochemistry and Molecular Biology, Brody School of Medicine, East Carolina University, Greenville, NC, USA.
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3
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Raustad N, Dai Y, Iinishi A, Mohapatra A, Soo MW, Hay E, Hernandez GM, Geisinger E. A phosphorylation signal activates genome-wide transcriptional control by BfmR, the global regulator of Acinetobacter resistance and virulence. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.06.16.599214. [PMID: 38948834 PMCID: PMC11212878 DOI: 10.1101/2024.06.16.599214] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/02/2024]
Abstract
The nosocomial pathogen Acinetobacter baumannii is a major threat to human health. The sensor kinase-response regulator system, BfmS-BfmR, is essential to multidrug resistance and virulence in the bacterium and represents a potential antimicrobial target. Important questions remain about how the system controls resistance and pathogenesis. Although BfmR knockout alters expression of >1000 genes, its direct regulon is undefined. Moreover, how phosphorylation controls the regulator is unclear. Here, we address these problems by combining mutagenesis, ChIP-seq, and in vitro phosphorylation to study the functions of phospho-BfmR. We show that phosphorylation is required for BfmR-mediated gene regulation, antibiotic resistance, and sepsis development in vivo. Consistent with activating the protein, phosphorylation induces dimerization and target DNA affinity. Integrated analysis of genome-wide binding and transcriptional profiles of BfmR led to additional key findings: (1) Phosphorylation dramatically expands the number of genomic sites BfmR binds; (2) DNA recognition involves a direct repeat motif widespread across promoters; (3) BfmR directly regulates 303 genes as activator (eg, capsule, peptidoglycan, and outer membrane biogenesis) or repressor (pilus biogenesis); (4) BfmR controls several non-coding sRNAs. These studies reveal the centrality of a phosphorylation signal in driving A. baumannii disease and disentangle the extensive pathogenic gene-regulatory network under its control.
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Affiliation(s)
- Nicole Raustad
- Department of Biology, Northeastern University, Boston, MA 02115, USA
| | - Yunfei Dai
- Department of Biology, Northeastern University, Boston, MA 02115, USA
| | - Akira Iinishi
- Antimicrobial Discovery Center, Department of Biology, Northeastern University, Boston, MA 02115, USA
| | - Arpita Mohapatra
- Department of Biology, Northeastern University, Boston, MA 02115, USA
| | - Mark W. Soo
- Department of Biology, Northeastern University, Boston, MA 02115, USA
| | - Everett Hay
- Department of Biology, Northeastern University, Boston, MA 02115, USA
| | | | - Edward Geisinger
- Department of Biology, Northeastern University, Boston, MA 02115, USA
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Girija ASS. Acinetobacter baumannii as an oro-dental pathogen: a red alert!! J Appl Oral Sci 2024; 32:e20230382. [PMID: 38747806 PMCID: PMC11090480 DOI: 10.1590/1678-7757-2023-0382] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2023] [Accepted: 03/01/2024] [Indexed: 05/19/2024] Open
Abstract
OBJECTIVES This review highlights the existence and association of Acinetobacter baumannii with the oro-dental diseases, transforming this systemic pathogen into an oral pathogen. The review also hypothesizes possible reasons for the categorization of this pathogen as code blue due to its stealthy entry into the oral cavity. METHODOLOGY Study data were retrieved from various search engines reporting specifically on the association of A. baumannii in dental diseases and tray set-ups. Articles were also examined regarding obtained outcomes on A. baumannii biofilm formation, iron acquisitions, magnitude of antimicrobial resistance, and its role in the oral cancers. RESULTS A. baumannii is associated with the oro-dental diseases and various virulence factors attribute for the establishment and progression of oro-mucosal infections. Its presence in the oral cavity is frequent in oral microbiomes, conditions of impaired host immunity, age related illnesses, and hospitalized individuals. Many sources also contribute for its prevalence in the dental health care environment and the presence of drug resistant traits is also observed. Its association with oral cancers and oral squamous cell carcinoma is also evident. CONCLUSIONS The review calls for awareness on the emergence of A. baumannii in dental clinics and for the need for educational programs to monitor and control the sudden outbreaks of such virulent and resistant traits in the dental health care settings.
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Affiliation(s)
- A S Smiline Girija
- Saveetha Institute of Medical and Technical Sciences (SIMATS), Saveetha Dental College and Hospitals, Department of Microbiology, Chennai-600077, Tamilnadu, India
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5
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Brychcy M, Nguyen B, Tierney GA, Casula P, Kokodynski A, Godoy VG. The metabolite vanillic acid regulates Acinetobacter baumannii surface attachment. Mol Microbiol 2024; 121:833-849. [PMID: 38308563 DOI: 10.1111/mmi.15234] [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: 10/20/2023] [Revised: 01/17/2024] [Accepted: 01/19/2024] [Indexed: 02/05/2024]
Abstract
The nosocomial bacterium Acinetobacter baumannii is protected from antibiotic treatment by acquiring antibiotic resistances and by forming biofilms. Cell attachment, one of the first steps in biofilm formation, is normally induced by environmental metabolites. We hypothesized that vanillic acid (VA), the oxidized form of vanillin and a widely available metabolite, may play a role in A. baumannii cell attachment. We first discovered that A. baumannii actively breaks down VA through the evolutionarily conserved vanABKP genes. These genes are under the control of the repressor VanR, which we show binds directly to VanR binding sites within the vanABKP genes bidirectional promoter. VA in turn counteracts VanR inhibition. We identified a VanR binding site and searched for it throughout the genome, especially in pili encoding promoter genes. We found a VanR binding site in the pilus encoding csu operon promoter and showed that VanR binds specifically to it. As expected, a strain lacking VanR overproduces Csu pili and makes robust biofilms. Our study uncovers the role that VA plays in facilitating the attachment of A. baumannii cells to surfaces, a crucial step in biofilm formation. These findings provide valuable insights into a previously obscure catabolic pathway with significant clinical implications.
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Affiliation(s)
- Merlin Brychcy
- Department of Biology, Northeastern University, Boston, Massachusetts, USA
| | - Brian Nguyen
- Department of Biology, Northeastern University, Boston, Massachusetts, USA
| | | | - Pranav Casula
- Department of Biology, Northeastern University, Boston, Massachusetts, USA
| | - Alexis Kokodynski
- Department of Biology, Northeastern University, Boston, Massachusetts, USA
| | - Veronica G Godoy
- Department of Biology, Northeastern University, Boston, Massachusetts, USA
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Ching C, Brychcy M, Nguyen B, Muller P, Pearson AR, Downs M, Regan S, Isley B, Fowle W, Chai Y, Godoy VG. RecA levels modulate biofilm development in Acinetobacter baumannii. Mol Microbiol 2024; 121:196-212. [PMID: 37918886 DOI: 10.1111/mmi.15188] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2023] [Revised: 10/06/2023] [Accepted: 10/17/2023] [Indexed: 11/04/2023]
Abstract
Infections caused by Acinetobacter baumannii, a Gram-negative opportunistic pathogen, are difficult to eradicate due to the bacterium's propensity to quickly gain antibiotic resistances and form biofilms, a protective bacterial multicellular community. The A. baumannii DNA damage response (DDR) mediates the antibiotic resistance acquisition and regulates RecA in an atypical fashion; both RecALow and RecAHigh cell types are formed in response to DNA damage. The findings of this study demonstrate that the levels of RecA can influence formation and dispersal of biofilms. RecA loss results in surface attachment and prominent biofilms, while elevated RecA leads to diminished attachment and dispersal. These findings suggest that the challenge to treat A. baumannii infections may be explained by the induction of the DDR, common during infection, as well as the delicate balance between maintaining biofilms in low RecA cells and promoting mutagenesis and dispersal in high RecA cells. This study underscores the importance of understanding the fundamental biology of bacteria to develop more effective treatments for infections.
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Affiliation(s)
- Carly Ching
- Department of Biology, Northeastern University, Boston, Massachusetts, USA
| | - Merlin Brychcy
- Department of Biology, Northeastern University, Boston, Massachusetts, USA
| | - Brian Nguyen
- Department of Biology, Northeastern University, Boston, Massachusetts, USA
| | - Paul Muller
- Department of Biology, Northeastern University, Boston, Massachusetts, USA
| | | | - Margaret Downs
- Department of Biology, Northeastern University, Boston, Massachusetts, USA
| | - Samuel Regan
- Department of Biology, Northeastern University, Boston, Massachusetts, USA
| | - Breanna Isley
- Department of Biology, Northeastern University, Boston, Massachusetts, USA
| | - William Fowle
- Department of Biology, Northeastern University, Boston, Massachusetts, USA
| | - Yunrong Chai
- Department of Biology, Northeastern University, Boston, Massachusetts, USA
| | - Veronica G Godoy
- Department of Biology, Northeastern University, Boston, Massachusetts, USA
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Girija ASS. Prediction of Antigenic Vaccine Peptide Candidates From BfmRS Associated With Biofilm Formation in Acinetobacter baumannii. Cureus 2023; 15:e47804. [PMID: 38022156 PMCID: PMC10676731 DOI: 10.7759/cureus.47804] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2023] [Accepted: 10/27/2023] [Indexed: 12/01/2023] Open
Abstract
INTRODUCTION A. baumannii is categorized as a priority pathogen due to its propensity for multi-drug resistance, exhibiting resistance against the last resort of antibiotics. It is also considered a potent nosocomial pathogen, so targeting the microbe using novel strategies would be the need of the hour. In this context, the in-silico computational approach would serve the best to design the possible epitope peptides, which may be further considered for the experimental trials for their immunological response. Objective: To predict the immune-dominant epitope peptide candidates against the bfmR and bfmS proteins mediating the two-component system adaptation in the formation of biofilm in A. baumannii. MATERIALS AND METHODS 11 different FASTA sequences of bfmR and bfmS from A. baumannii strains retrieved based on the blast-p similarity search tool were subjected to linear epitope B-cell epitope predictions under the IEDB B-cell epitope prediction server. Further analysis on antigenicity, allergenicity, and toxigenicity was achieved using the AntigenPro, Vaxijen, and AlgPred tools, with the physical and chemical properties evaluated using the Expasy Protparam server. Selection of the immunodominant peptides for T-cells was done through the databases under IEDB. The final assessment of protein-TLR2 interactions was done by MHC cluster servers. RESULTS Four peptide sequences (E1-E4) were predicted for B-cell dominance, with E1, E2, and E4 as probable antigens. All were soluble and non-toxigenic. E1 and E3 were considered non-allergens. GRAVY values were negative for all the peptides, indicating the protein to be hydrophilic in nature. Analysis of the T-cell epitopes was promising, with 100% conservancy for class-I HLA alleles, high interaction scores for similarity with TLR2, and more hydrogen bonds for E2, followed by other epitope peptides. CONCLUSION The promising four epitopes, as predicted for bfmR and bfmS in the present study, suggest their potent role as possible candidates for the design of vaccines targeting the TCS of A. baumannii, recommending further in vitro and in vivo experimental validation.
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Affiliation(s)
- A S Smiline Girija
- Department of Microbiology, Saveetha Dental College and Hospitals, Saveetha Institute of Medical and Technical Sciences [SIMATS] Saveetha University, Chennai, IND
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Mumtaz L, Farid A, Yousef Alomar S, Ahmad N, Nawaz A, Andleeb S, Amin A. Assesment of polyphenolic compounds against biofilms produced by clinical Acinetobacter baumannii strains using in silico and in vitro models. Saudi J Biol Sci 2023; 30:103743. [PMID: 37564783 PMCID: PMC10410175 DOI: 10.1016/j.sjbs.2023.103743] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2023] [Revised: 07/05/2023] [Accepted: 07/14/2023] [Indexed: 08/12/2023] Open
Abstract
Several types of microbial infections are caused by Acinetobacter baumanii that has developed resistance to antimicrobial agents. We therefore investigated the role of plant polyphenols against A. baumannii using in silico and in vitro models. The clinical strains of A. baumannii were investigated for determination of resistance pattern and resistance mechanisms including efflux pump, extended spectrum beta lactamase, phenotype detection of AmpC production, and Metallo-β-lactamase. The polyphenolic compounds were docked against transcription regulator BfmR (PDB ID 6BR7) and antimicrobial, antibiofilm, and anti-quorum sensing activities were performed. The antibiogram studies showed that all isolated strains were resistant. Strain A77 was positive in Metallo-β-lactamase production. Similarly, none of strains were producers of AmpC, however, A77, A76, A75 had active efflux pumps. Molecular docking studies confirmed a strong binding affinity of Rutin and Catechin towards transcription regulator 6BR7. A significant antimicrobial activity was recorded in case of quercetin and syringic acid (MIC 3.1 µg/mL) followed by vanillic acid and caffeic acid (MIC 12.5 µg/mL). All tested compounds presented a strong antibiofilm activity against A. baumanii strain A77 (65 to 90%). It was concluded that all tested polyphenols samples posess antimicrobial and antibiofilm activities, and hence they may be utilized to treat multidrug resistance A. baumannii infections.
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Affiliation(s)
- Laraib Mumtaz
- Gomal Centre of Biochemistry and Biotechnology(GCBB), Gomal University, KPK, 29050 D.I.Khan, Pakistan
- Gomal Centre of Pharmaceutical Sciences, Faculty of Pharmacy, Gomal University, D.I.Khan 29050, Pakistan
| | - Arshad Farid
- Gomal Centre of Biochemistry and Biotechnology(GCBB), Gomal University, KPK, 29050 D.I.Khan, Pakistan
| | - Suliman Yousef Alomar
- Doping Research Chair, Zoology Department, College of Science, King Saud University, Riyadh 11451, Saudi Arabia
| | - Naushad Ahmad
- Department of Chemistry, College of Science, King Saud University, Riyadh 11451, Saudi Arabia
| | - Asif Nawaz
- Gomal Centre of Pharmaceutical Sciences, Faculty of Pharmacy, Gomal University, D.I.Khan 29050, Pakistan
| | - Saadia Andleeb
- Atta Ur Rehman School of Biological Sciences, National University of Science and Technology, Islamabad Pakistan
| | - Adnan Amin
- Gomal Centre of Pharmaceutical Sciences, Faculty of Pharmacy, Gomal University, D.I.Khan 29050, Pakistan
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Ratti A, Fassi EMA, Forlani F, Zangrossi M, Mori M, Cappitelli F, Roda G, Villa S, Villa F, Grazioso G. Unlocking the Antibiofilm Potential of Natural Compounds by Targeting the NADH:quinone Oxidoreductase WrbA. Antioxidants (Basel) 2023; 12:1612. [PMID: 37627607 PMCID: PMC10451263 DOI: 10.3390/antiox12081612] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2023] [Revised: 07/31/2023] [Accepted: 08/12/2023] [Indexed: 08/27/2023] Open
Abstract
Biofilm-dwelling cells endure adverse conditions, including oxidative imbalances. The NADH:quinone oxidoreductase enzyme WrbA has a crucial role in the mechanism of action of antibiofilm molecules such as ellagic and salicylic acids. This study aimed to exploit the potential of the WrbA scaffold as a valuable target for identifying antibiofilm compounds at non-lethal concentrations. A three-dimensional computational model, based on the published WrbA structure, was used to screen natural compounds from a virtual library of 800,000 compounds. Fisetin, morin, purpurogallin, NZ028, and NZ034, along with the reference compound ellagic acid, were selected. The antibiofilm effect of the molecules was tested at non-lethal concentrations evaluating the cell-adhesion of wild-type and WrbA-deprived Escherichia coli strains through fluorochrome-based microplate assays. It was shown that, except for NZ028, all of the selected molecules exhibited notable antibiofilm effects. Purpurogallin and NZ034 showed excellent antibiofilm performances at the lowest concentration of 0.5 μM, in line with ellagic acid. The observed loss of activity and the level of reactive oxygen species in the mutant strain, along with the correlation with terms contributing to the ligand-binding free energy on WrbA, strongly indicates the WrbA-dependency of purpurogallin and NZ034. Overall, the molecular target WrbA was successfully employed to identify active compounds at non-lethal concentrations, thus revealing, for the first time, the antibiofilm efficacy of purpurogallin and NZ034.
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Affiliation(s)
- Alessandro Ratti
- Department of Pharmaceutical Sciences, University of Milan, Via L. Mangiagalli 25, 20133 Milan, Italy
| | - Enrico M A Fassi
- Department of Pharmaceutical Sciences, University of Milan, Via L. Mangiagalli 25, 20133 Milan, Italy
| | - Fabio Forlani
- Department of Food Environmental and Nutritional Science (DeFENS), University of Milan, Via Celoria 2, 20133 Milan, Italy
| | - Maurizio Zangrossi
- Department of Food Environmental and Nutritional Science (DeFENS), University of Milan, Via Celoria 2, 20133 Milan, Italy
| | - Matteo Mori
- Department of Pharmaceutical Sciences, University of Milan, Via L. Mangiagalli 25, 20133 Milan, Italy
| | - Francesca Cappitelli
- Department of Food Environmental and Nutritional Science (DeFENS), University of Milan, Via Celoria 2, 20133 Milan, Italy
| | - Gabriella Roda
- Department of Pharmaceutical Sciences, University of Milan, Via L. Mangiagalli 25, 20133 Milan, Italy
| | - Stefania Villa
- Department of Pharmaceutical Sciences, University of Milan, Via L. Mangiagalli 25, 20133 Milan, Italy
| | - Federica Villa
- Department of Food Environmental and Nutritional Science (DeFENS), University of Milan, Via Celoria 2, 20133 Milan, Italy
| | - Giovanni Grazioso
- Department of Pharmaceutical Sciences, University of Milan, Via L. Mangiagalli 25, 20133 Milan, Italy
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Bai J, Raustad N, Denoncourt J, van Opijnen T, Geisinger E. Genome-wide phage susceptibility analysis in Acinetobacter baumannii reveals capsule modulation strategies that determine phage infectivity. PLoS Pathog 2023; 19:e1010928. [PMID: 37289824 PMCID: PMC10249906 DOI: 10.1371/journal.ppat.1010928] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2022] [Accepted: 04/27/2023] [Indexed: 06/10/2023] Open
Abstract
Phage have gained renewed interest as an adjunctive treatment for life-threatening infections with the resistant nosocomial pathogen Acinetobacter baumannii. Our understanding of how A. baumannii defends against phage remains limited, although this information could lead to improved antimicrobial therapies. To address this problem, we identified genome-wide determinants of phage susceptibility in A. baumannii using Tn-seq. These studies focused on the lytic phage Loki, which targets Acinetobacter by unknown mechanisms. We identified 41 candidate loci that increase susceptibility to Loki when disrupted, and 10 that decrease susceptibility. Combined with spontaneous resistance mapping, our results support the model that Loki uses the K3 capsule as an essential receptor, and that capsule modulation provides A. baumannii with strategies to control vulnerability to phage. A key center of this control is transcriptional regulation of capsule synthesis and phage virulence by the global regulator BfmRS. Mutations hyperactivating BfmRS simultaneously increase capsule levels, Loki adsorption, Loki replication, and host killing, while BfmRS-inactivating mutations have the opposite effect, reducing capsule and blocking Loki infection. We identified novel BfmRS-activating mutations, including knockouts of a T2 RNase protein and the disulfide formation enzyme DsbA, that hypersensitize bacteria to phage challenge. We further found that mutation of a glycosyltransferase known to alter capsule structure and bacterial virulence can also cause complete phage resistance. Finally, additional factors including lipooligosaccharide and Lon protease act independently of capsule modulation to interfere with Loki infection. This work demonstrates that regulatory and structural modulation of capsule, known to alter A. baumannii virulence, is also a major determinant of susceptibility to phage.
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Affiliation(s)
- Jinna Bai
- Department of Biology, Northeastern University, Boston, Massachusetts, United States of America
| | - Nicole Raustad
- Department of Biology, Northeastern University, Boston, Massachusetts, United States of America
| | - Jason Denoncourt
- Department of Biology, Northeastern University, Boston, Massachusetts, United States of America
| | - Tim van Opijnen
- Broad Institute of MIT and Harvard, CISID, Cambridge, Massachusetts, United States of America
| | - Edward Geisinger
- Department of Biology, Northeastern University, Boston, Massachusetts, United States of America
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11
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Milton ME, Cavanagh J. The Biofilm Regulatory Network from Bacillus subtilis: A Structure-Function Analysis. J Mol Biol 2023; 435:167923. [PMID: 36535428 DOI: 10.1016/j.jmb.2022.167923] [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: 10/06/2022] [Revised: 12/02/2022] [Accepted: 12/11/2022] [Indexed: 12/23/2022]
Abstract
Bacterial biofilms are notorious for their ability to protect bacteria from environmental challenges, most importantly the action of antibiotics. Bacillus subtilis is an extensively studied model organism used to understand the process of biofilm formation. A complex network of principal regulatory proteins including Spo0A, AbrB, AbbA, Abh, SinR, SinI, SlrR, and RemA, work in concert to transition B. subtilis from the free-swimming planktonic state to the biofilm state. In this review, we explore, connect, and summarize decades worth of structural and biochemical studies that have elucidated this protein signaling network. Since structure dictates function, unraveling aspects of protein molecular mechanisms will allow us to devise ways to exploit critical features of the biofilm regulatory pathway, such as possible therapeutic intervention. This review pools our current knowledge base of B. subtilis biofilm regulatory proteins and highlights potential therapeutic intervention points.
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Affiliation(s)
- Morgan E Milton
- Department of Biochemistry and Molecular Biology, The Brody School of Medicine, East Carolina University, NC 27834, USA.
| | - John Cavanagh
- Department of Biochemistry and Molecular Biology, The Brody School of Medicine, East Carolina University, NC 27834, USA.
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12
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BfmRS encodes a regulatory system involved in light signal transduction modulating motility and desiccation tolerance in the human pathogen Acinetobacter baumannii. Sci Rep 2023; 13:175. [PMID: 36604484 PMCID: PMC9814549 DOI: 10.1038/s41598-022-26314-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2022] [Accepted: 12/13/2022] [Indexed: 01/06/2023] Open
Abstract
We have previously shown that Acinetobacter baumannii as well as other relevant clinical bacterial pathogens such as Staphylococcus aureus and Pseudomonas aeruginosa, perceive and respond to light at 37 °C, the normal temperature in mammal hosts. In this work, we present evidence indicating that the two-component system BfmRS transduces a light signal in A. baumannii at this temperature, showing selective involvement of the BfmR and BfmS components depending on the specific cellular process. In fact, both BfmR and BfmS participate in modulation of motility by light, while only BfmR is involved in light regulation of desiccation tolerance in this microorganism. Neither BfmR nor BfmS contain a photoreceptor domain and then most likely, the system is sensing light indirectly. Intriguingly, this system inhibits blsA expression at 37 °C, suggesting antagonistic functioning of both signaling systems. Furthermore, we present evidence indicating that the phosphorylatable form of BfmR represses motility. Overall, we provide experimental evidence on a new biological function of this multifaceted system that broadens our understanding of A. baumannii's physiology and responses to light.
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13
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Zeczycki TN, Milton ME, Jung D, Thompson RJ, Jaimes FE, Hondros AD, Palethorpe S, Melander C, Cavanagh J. 2-Aminoimidazole Analogs Target PhoP Altering DNA Binding Activity and Affect Outer Membrane Stability in Gram-Negative Bacteria. Biochemistry 2022; 61:2948-2960. [DOI: 10.1021/acs.biochem.2c00560] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
Affiliation(s)
- Tonya N. Zeczycki
- Department of Biochemistry and Molecular Biology, Brody School of Medicine, East Carolina University, Greenville, North Carolina27834, United States
| | - Morgan E. Milton
- Department of Biochemistry and Molecular Biology, Brody School of Medicine, East Carolina University, Greenville, North Carolina27834, United States
| | - David Jung
- Agile Sciences Inc., 617 Hutton Street, Raleigh, North Carolina27606, United States
| | - Richele J. Thompson
- Department of Biochemistry and Molecular Biology, Brody School of Medicine, East Carolina University, Greenville, North Carolina27834, United States
| | - Felicia E. Jaimes
- Department of Biochemistry and Molecular Biology, Brody School of Medicine, East Carolina University, Greenville, North Carolina27834, United States
| | - Alexander D. Hondros
- Department of Biochemistry and Molecular Biology, Brody School of Medicine, East Carolina University, Greenville, North Carolina27834, United States
| | - Samantha Palethorpe
- Department of Microbiology and Immunology, Brody School of Medicine, East Carolina University, Greenville, North Carolina27834, United States
| | - Christian Melander
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana46556, United States
| | - John Cavanagh
- Department of Biochemistry and Molecular Biology, Brody School of Medicine, East Carolina University, Greenville, North Carolina27834, United States
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14
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Kim HJ, Kim NY, Ko SY, Park SY, Oh MH, Shin MS, Lee YC, Lee JC. Complementary Regulation of BfmRS Two-Component and AbaIR Quorum Sensing Systems to Express Virulence-Associated Genes in Acinetobacter baumannii. Int J Mol Sci 2022; 23:13136. [PMID: 36361923 PMCID: PMC9657202 DOI: 10.3390/ijms232113136] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2022] [Revised: 10/22/2022] [Accepted: 10/26/2022] [Indexed: 09/22/2023] Open
Abstract
Acinetobacter baumannii expresses various virulence factors to adapt to hostile environments and infect susceptible hosts. This study investigated the regulatory network of the BfmRS two-component and AbaIR quorum sensing (QS) systems in the expression of virulence-associated genes in A. baumannii ATCC 17978. The ΔbfmS mutant exhibited a significant decrease in surface motility, which presumably resulted from the low expression of pilT and A1S_0112-A1S_0119 gene cluster. The ΔbfmR mutant displayed a significant reduction in biofilm and pellicle formation due to the low expression of csu operon. The deletion of abaR did not affect the expression of bfmR or bfmS. However, the expression of abaR and abaI was upregulated in the ΔbfmR mutant. The ΔbfmR mutant also produced more autoinducers than did the wild-type strain, suggesting that BfmR negatively regulates the AbaIR QS system. The ΔbfmS mutant exhibited no autoinducer production in the bioassay system. The expression of the A1S_0112-A1S_0119 gene cluster was downregulated in the ΔabaR mutant, whereas the expression of csu operon was upregulated in this mutant with a high cell density. In conclusion, for the first time, we demonstrated that the BfmRS-AbaIR QS system axis regulated the expression of virulence-associated genes in A. baumannii. This study provides new insights into the complex network system involved in the regulation of virulence-associated genes underlying the pathogenicity of A. baumannii.
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Affiliation(s)
- Hyo-Jeong Kim
- Department of Microbiology, School of Medicine, Kyungpook National University, Daegu 41944, Korea
| | - Na-Yeong Kim
- Department of Microbiology, School of Medicine, Kyungpook National University, Daegu 41944, Korea
| | - Seo-Yeon Ko
- Department of Microbiology, School of Medicine, Kyungpook National University, Daegu 41944, Korea
| | - Seong-Yong Park
- Department of Microbiology, School of Medicine, Kyungpook National University, Daegu 41944, Korea
| | - Man-Hwan Oh
- Department of Microbiology, College of Science and Technology, Dankook University, Cheonan 16890, Korea
| | - Min-Sang Shin
- Department of Microbiology, School of Medicine, Kyungpook National University, Daegu 41944, Korea
| | - Yoo-Chul Lee
- Department of Microbiology, School of Medicine, Kyungpook National University, Daegu 41944, Korea
| | - Je-Chul Lee
- Department of Microbiology, School of Medicine, Kyungpook National University, Daegu 41944, Korea
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15
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Lokhande KB, Pawar SV, Madkaiker S, Nawani N, Venkateswara SK, Ghosh P. High throughput virtual screening and molecular dynamics simulation analysis of phytomolecules against BfmR of Acinetobacter baumannii: anti-virulent drug development campaign. J Biomol Struct Dyn 2022; 41:2698-2712. [PMID: 35156902 DOI: 10.1080/07391102.2022.2038271] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Acinetobacter baumannii is a notorious multidrug resistant bacterium responsible for several hospital acquired infections assisted by its capacity to develop biofilms. A. baumannii BfmR (RstA), a response regulator from the BfmR/S two-component signal transduction system, is the major controller of A. baumannii biofilm development and formation. As a result, BfmR represents a novel target for anti-biofilm treatment against A. baumannii. The discovery of the high-resolution crystal structure of BfmR provides a good chance for computational screening of its probable inhibitors. Therefore, in this study we aim to search new, less toxic, and natural BfmR inhibitors from 8450 phytomolecules available in the Indian Medicinal Plants, Phytochemistry and Therapeutic (IMPPAT) database by analyzing molecular docking against BfmR (PDB ID: 6BR7). Out of these 8450 phytomolecules 6742 molecules were successfully docked with BfmR with the docking score range -6.305 kcal/mol to +5.120 kcal/mol. Structure based-molecular docking (SB-MD) and ADMET (absorption, distribution, metabolism, excretion, & toxicity) profile examination revealed that Norepinephrine, Australine, Calystegine B3, 7,7 A-Diepialexine, and Alpha-Methylnoradrenaline phytocompounds strongly binds to the active site residues of BfmR. Furthermore, molecular dynamics simulation (MDS) studies for 100 ns and the binding free energy (MM/GBSA) analysis elucidated the binding mechanism of Calystegine B3, 7,7 A-Diepialexine, and Alpha-Methylnoradrenaline to BfmR. In summary, these phytocompounds seems to have the promising molecules against BfmR, and thus necessitates further verification by both in vitro and in vivo experiments. HighlightsBfmR plays a key role in biofilm development and exopolysaccharide (EPS) synthesis in A. baumannii.Computational approach to search for promising BfmR inhibitors from IMPAAT database.The lead phytomolecules such as Calystegine B3, 7,7 A-Diepialexine, and Alpha-Methylnoradrenaline displayed significant binding with BfmR active site.The outcome of BfmR binding phytomolecules has broadened the scope of hit molecules validation.Communicated by Ramaswamy H. Sarma.
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Affiliation(s)
- Kiran Bharat Lokhande
- Dr. D. Y. Patil Vidyapeeth, Bioinformatics Research Laboratory, Dr. D. Y. Patil Biotechnology and Bioinformatics Institute, Pune, India
| | - Sarika Vishnu Pawar
- Dr. D. Y. Patil Vidyapeeth, Microbial Diversity Research Centre, Dr. D. Y. Patil Biotechnology and Bioinformatics Institute, Pune, India
| | - Smriti Madkaiker
- Dr. D. Y. Patil Vidyapeeth, Microbial Diversity Research Centre, Dr. D. Y. Patil Biotechnology and Bioinformatics Institute, Pune, India
| | - Neelu Nawani
- Dr. D. Y. Patil Vidyapeeth, Microbial Diversity Research Centre, Dr. D. Y. Patil Biotechnology and Bioinformatics Institute, Pune, India
| | - Swamy K Venkateswara
- Bioinformatics Research Group, MIT School of Bioengineering Sciences & Research, MIT-ADT University, Pune, Maharashtra, India
| | - Payel Ghosh
- Bioinformatics Centre, Savitribai Phule Pune University, Pune, Maharashtra, India
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16
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Jothipandiyan S, Suresh D, Sankaran SV, Thamotharan S, Shanmugasundaram K, Vincent P, Sekaran S, Gowrishankar S, Pandian SK, Paramasivam N. Heteroleptic pincer palladium(II) complex coated orthopedic implants impede the AbaI/AbaR quorum sensing system and biofilm development by Acinetobacter baumannii. BIOFOULING 2022; 38:55-70. [PMID: 34961388 DOI: 10.1080/08927014.2021.2015336] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/26/2021] [Revised: 12/01/2021] [Accepted: 12/01/2021] [Indexed: 06/14/2023]
Abstract
Implant-associated infections mediated by Acinetobacter baumannii biofilms have become a major concern in the healthcare sector. As biofilm formation by this important pathogen is mediated by quorum sensing, quorum sensing inhibitors (QSI) have gained much attention. The present study confirms that novel thiazolinyl-picolinamide based palladium(II) complexes had good biofilm disruptive and QSI properties against A. baumannii. Key QS-mediated virulence factors like pili mediated surface motility and polysaccharide production were inhibited by the best Pd(II) complex (E). This also showed potent inhibitory activity against both the standard and clinical strains of A. baumannii. Molecular docking analysis also proved the potent binding affinity of Pd(II)-E with the virulence targets. The Pd(II) complex also disrupted preformed biofilms and down-regulated the expression of QS mediated virulence genes in the biofilms established on implant material (titanium plates). As a whole, the present study showed that the novel thiazolinyl-picolinamide based Pd(II) complexes offer a promising anti-infective strategy to combat biofilm-mediated implant infections.
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Affiliation(s)
- Sowndarya Jothipandiyan
- Biofilm Biology Laboratory, Centre for Research on Infectious Diseases (CRID), School of Chemical and Biotechnology, SASTRA Deemed University, Thanjavur, Tamil Nadu, India
| | - Devarajan Suresh
- Department of Chemistry, School of Chemical and Biotechnology, SASTRA Deemed University, Thanjavur, Tamil Nadu, India
| | - Sankaran Venkatachalam Sankaran
- Biomolecular Crystallography Laboratory, Department of Bioinformatics, School of Chemical and Biotechnology, SASTRA Deemed University, Thanjavur, Tamil Nadu, India
| | - Subbiah Thamotharan
- Biomolecular Crystallography Laboratory, Department of Bioinformatics, School of Chemical and Biotechnology, SASTRA Deemed University, Thanjavur, Tamil Nadu, India
| | | | - Preethi Vincent
- Bone Biology and Repair laboratory, School of Chemical and Biotechnology, SASTRA Deemed University, Thanjavur, Tamil Nadu, India
| | - Saravanan Sekaran
- Bone Biology and Repair laboratory, School of Chemical and Biotechnology, SASTRA Deemed University, Thanjavur, Tamil Nadu, India
- Department of Pharmacology, Saveetha Dental college and hospitals, Saveetha institute for medical and Technical sciences, Saveetha University, Chennai, India
| | | | | | - Nithyanand Paramasivam
- Biofilm Biology Laboratory, Centre for Research on Infectious Diseases (CRID), School of Chemical and Biotechnology, SASTRA Deemed University, Thanjavur, Tamil Nadu, India
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17
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Upmanyu K, Haq QMR, Singh R. Factors mediating Acinetobacter baumannii biofilm formation: Opportunities for developing therapeutics. CURRENT RESEARCH IN MICROBIAL SCIENCES 2022; 3:100131. [PMID: 35909621 PMCID: PMC9325880 DOI: 10.1016/j.crmicr.2022.100131] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
A. baumannii rapidly acquires antimicrobial resistance and causes biofilm associated infections. Strategies to target intrinsic factors mediating A. baumannii biofilm formation offer therapeutic prospects. Antimicrobial polymers and coating medical devices with antibiofilm agents may prevent biofilm associated infections. Biofilm matrix or regulatory mechanisms such as quorum sensing are potential targets for treating chronic infections. Phage therapy, photodynamic therapy and nanoparticle therapy are novel promising approaches for treating biofilm associated infections.
Acinetobacter baumannii has notably become a superbug due to its mounting risk of infection and escalating rates of antimicrobial resistance, including colistin, the last-resort antibiotic. Its propensity to form biofilm on biotic and abiotic surfaces has contributed to the majority of nosocomial infections. Bacterial cells in biofilms are resistant to antibiotics and host immune response, and pose challenges in treatment. Therefore current scenario urgently requires the development of novel therapeutic strategies for successful treatment outcomes. This article provides a holistic understanding of sequential events and regulatory mechanisms directing A. baumannii biofilm formation. Understanding the key factors functioning and regulating the biofilm machinery of A. baumannii will provide us insight to develop novel approaches to combat A. baumannii infections. Further, the review article deliberates promising strategies for the prevention of biofilm formation on medically relevant substances and potential therapeutic strategies for the eradication of preformed biofilms which can help tackle biofilm-associated A. baumannii infections. Advances in emerging therapeutic opportunities such as phage therapy, nanoparticle therapy and photodynamic therapy are also discussed to comprehend the current scenario and future outlook for the development of successful treatment against biofilm-associated A. baumannii infections.
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18
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Pandey M, Wasnik K, Gupta S, Singh M, Patra S, Gupta P, Pareek D, Maity S, Tilak R, Paik P. Targeted specific inhibition of bacterial and Candida species by mesoporous Ag/Sn–SnO2 composite nanoparticles: in silico and in vitro investigation. RSC Adv 2022; 12:1105-1120. [PMID: 35425144 PMCID: PMC8978812 DOI: 10.1039/d1ra07594b] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2021] [Accepted: 12/15/2021] [Indexed: 02/06/2023] Open
Abstract
Invasive bacterial and fungal infections have notably increased the burden on the health care system and especially in immune compromised patients. These invasive bacterial and fungal species mimic and interact with the host extracellular matrix and increase the adhesion and internalization into the host system. Further, increased resistance of traditional antibiotics/antifungal drugs led to the demand for other therapeutics and preventive measures. Presently, metallic nanoparticles have wide applications in health care sectors. The present study has been designed to evaluate the advantage of Ag/Sn–SnO2 composite nanoparticles over the single oxide/metallic nanoparticles. By using in silico molecular docking approaches, herein we have evaluated the effects of Ag/Sn–SnO2 nanoparticles on adhesion and invasion responsible molecular targets such as LpfD (E. coli), Als3 (C. albicans) and on virulence/resistance causing PqsR (P. aeruginosa), RstA (Bmfr) (A. baumannii), FoxA (K. pneumonia), Hsp90 and Cyp51 (C. albicans). These Ag/Sn–SnO2 nanoparticles exhibited higher antimicrobial activities, especially against the C. albicans, which are the highest ever reported results. Further, Ag/Sn–SnO2 NPs exhibited interaction with the heme proionate residues such as Lys143, His468, Tyr132, Arg381, Phe105, Gly465, Gly464, Ile471 and Ile304 by forming hydrogen bonds with the Arg 381 residue of lanosterol 1 4α-demethylase and increased the inhibition of the Candida strains. Additionally, the Ag/Sn–SnO2 nanoparticles exhibited extraordinary inhibitory properties by targeting different proteins of bacteria and Candida species followed by several molecular pathways which indicated that it can be used to eliminate the resistance to traditional antibiotics. Mesoporous Ag/Sn–SnO2 composite nanoparticles exhibits extraordinary inhibitory properties by targeting different proteins of bacteria and Candida species which can be used to eliminate the resistance of traditional antibiotics.![]()
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Affiliation(s)
- Monica Pandey
- School of Engineering Sciences and Technology, University of Hyderabad, Telangana, 500046, India
| | - Kirti Wasnik
- School of Biomedical Engineering, Indian Institute of Technology, Banaras Hindu University (BHU), Varanasi, Uttar Pradesh, 221005, India
| | - Shubhra Gupta
- School of Biomedical Engineering, Indian Institute of Technology, Banaras Hindu University (BHU), Varanasi, Uttar Pradesh, 221005, India
| | - Monika Singh
- School of Biomedical Engineering, Indian Institute of Technology, Banaras Hindu University (BHU), Varanasi, Uttar Pradesh, 221005, India
| | - Sukanya Patra
- School of Biomedical Engineering, Indian Institute of Technology, Banaras Hindu University (BHU), Varanasi, Uttar Pradesh, 221005, India
| | - Premshankar Gupta
- School of Biomedical Engineering, Indian Institute of Technology, Banaras Hindu University (BHU), Varanasi, Uttar Pradesh, 221005, India
| | - Divya Pareek
- School of Biomedical Engineering, Indian Institute of Technology, Banaras Hindu University (BHU), Varanasi, Uttar Pradesh, 221005, India
| | - Somedutta Maity
- School of Engineering Sciences and Technology, University of Hyderabad, Telangana, 500046, India
| | - Ragini Tilak
- Institute of Medical Sciences, Banaras Hindu University (BHU), Varanasi, Uttar Pradesh, 221005, India
| | - Pradip Paik
- School of Biomedical Engineering, Indian Institute of Technology, Banaras Hindu University (BHU), Varanasi, Uttar Pradesh, 221005, India
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19
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Acinetobacter baumannii regulates its stress responses via the BfmRS two-component regulatory system. J Bacteriol 2021; 204:e0049421. [PMID: 34871031 DOI: 10.1128/jb.00494-21] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Acinetobacter baumannii is a common nosocomial pathogen that utilizes numerous mechanisms to aid its survival in both the environment and in the host. Coordination of such mechanisms requires an intricate regulatory network. We report here that A. baumannii can directly regulate several stress-related pathways via the two-component regulatory system, BfmRS. Similar to previous studies, results from transcriptomic analysis showed that mutation of the BfmR response regulator causes dysregulation of genes required for the oxidative stress response, the osmotic stress response, the misfolded protein/heat shock response, Csu pili/fimbriae production, and capsular polysaccharide biosynthesis. We also found that the BfmRS system is involved in controlling siderophore biosynthesis and transport, and type IV pili production. We provide evidence that BfmR binds to various stress-related promoter regions and show that BfmR alone can directly activate transcription of some stress-related genes. Additionally, we show that the BfmS sensor kinase acts as a BfmR phosphatase to negatively regulate BfmR activity. This work highlights the importance of the BfmRS system in promoting survival of A. baumannii. Importance Acinetobacter baumannii is a nosocomial pathogen that has extremely high rates of multidrug resistance. This organism's ability to endure stressful conditions is a key part of its ability to spread in the hospital environment and cause infections. Unlike other members of the γ-proteobacteria, A. baumannii does not encode a homolog of the RpoS sigma factor to coordinate its stress response. Here, we demonstrate that the BfmRS two-component system directly controls the expression of multiple stress resistance genes. Our findings suggest that BfmRS is central to a unique scheme of general stress response regulation by A. baumannii.
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20
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Pandey M, Singh M, Wasnik K, Gupta S, Patra S, Gupta PS, Pareek D, Chaitanya NSN, Maity S, Reddy ABM, Tilak R, Paik P. Targeted and Enhanced Antimicrobial Inhibition of Mesoporous ZnO-Ag 2O/Ag, ZnO-CuO, and ZnO-SnO 2 Composite Nanoparticles. ACS OMEGA 2021; 6:31615-31631. [PMID: 34869986 PMCID: PMC8637601 DOI: 10.1021/acsomega.1c04139] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/03/2021] [Accepted: 11/08/2021] [Indexed: 05/04/2023]
Abstract
In this work, mesoporous (pore size below 4 nm) composite nanoparticles of ZnO-Ag2O/Ag, ZnO-CuO, and ZnO-SnO2 of size d ≤ 10 nm (dia.) have been synthesized through the in situ solvochemical reduction method using NaBH4. These composite nanoparticles exhibited excellent killing efficacy against Gram-positive/negative bacterial and fungal strains even at a very low dose of 0.010 μg/mL. Additionally, by applying the in silico docking approach, the nanoparticles and microorganism-specific targeted proteins and their interactions have been identified to explain the best anti-bacterial/anti-fungal activities of these composites. For this purpose, the virulence and resistance causing target proteins such as PqsR, RstA, FosA, and Hsp90 of Pseudomonas aeruginosa, Acinetobacter baumannii, Klebsiella pneumoniae, and Candida albicans have been identified to find out the best inhibitory action mechanisms involved. From the in vitro study, it is revealed that all the composite nanoparticle types used here can act as potent antimicrobial components. All the composite nanoparticles have exhibited excellent inhibition against the microorganisms compared to their constituent single metal or metal oxide nanoparticles. Among the nanoparticle types, the ZnO-Ag2O/Ag composite nanoparticles exhibited the best inhibition activity compared to the other reported nanoparticles. The microorganisms which are associated with severe infections lead to the multidrug resistance and have become a huge concern in the healthcare sector. Conventional organic antibiotics are less stable at a higher temperature. Therefore, based on the current demands, this work has been focused on designing inorganic antibiotics which possess stability even under harsh conditions. In this direction, our developed composite nanoparticles were explored for potential uses in the healthcare technology, and they may solve many problems in global emergency and epidemics caused by the microorganisms.
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Affiliation(s)
- Monica Pandey
- School
of Engineering Sciences and Technology, University of Hyderabad, Hyderabad, Telangana 500046, India
| | - Monika Singh
- School
of Biomedical Engineering, Indian Institute of Technology, Banaras Hindu University (BHU), Varanasi, Uttar Pradesh 221005, India
| | - Kirti Wasnik
- School
of Biomedical Engineering, Indian Institute of Technology, Banaras Hindu University (BHU), Varanasi, Uttar Pradesh 221005, India
| | - Shubhra Gupta
- School
of Biomedical Engineering, Indian Institute of Technology, Banaras Hindu University (BHU), Varanasi, Uttar Pradesh 221005, India
| | - Sukanya Patra
- School
of Biomedical Engineering, Indian Institute of Technology, Banaras Hindu University (BHU), Varanasi, Uttar Pradesh 221005, India
| | - Prem Shankar Gupta
- School
of Biomedical Engineering, Indian Institute of Technology, Banaras Hindu University (BHU), Varanasi, Uttar Pradesh 221005, India
| | - Divya Pareek
- School
of Biomedical Engineering, Indian Institute of Technology, Banaras Hindu University (BHU), Varanasi, Uttar Pradesh 221005, India
| | - Nyshadham Sai Naga Chaitanya
- Department
of Animal Science, School of Life Sciences, University of Hyderabad, Hyderabad, Telangana 500046, India
| | - Somedutta Maity
- School
of Engineering Sciences and Technology, University of Hyderabad, Hyderabad, Telangana 500046, India
| | - Aramati B. M. Reddy
- Department
of Animal Science, School of Life Sciences, University of Hyderabad, Hyderabad, Telangana 500046, India
| | - Ragini Tilak
- Institute
of Medical Sciences, Banaras Hindu University
(BHU), Varanasi, Uttar Pradesh 221005, India
| | - Pradip Paik
- School
of Biomedical Engineering, Indian Institute of Technology, Banaras Hindu University (BHU), Varanasi, Uttar Pradesh 221005, India
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21
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Palethorpe S, Milton ME, Pesci EC, Cavanagh J. Structure of the Acinetobacter baumannii PmrA receiver domain and insights into clinical mutants affecting DNA-binding and promoting colistin resistance. J Biochem 2021; 170:787-800. [PMID: 34585233 DOI: 10.1093/jb/mvab102] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2021] [Accepted: 09/22/2021] [Indexed: 11/14/2022] Open
Abstract
Acinetobacter baumannii is an insidious emerging nosocomial pathogen that has developed resistance to all available antimicrobials, including the last resort antibiotic, colistin. Colistin resistance often occurs due to mutations in the PmrAB two component regulatory system. To better understand the regulatory mechanisms contributing to colistin resistance, we have biochemically characterized the A. baumannii PmrA response regulator. Initial DNA-binding analysis shows that A. baumannii PmrA bound to the Klebsiella pneumoniae PmrA box motif. This prompted analysis of the putative A. baumannii PmrAB regulon which indicated that the A. baumannii PmrA consensus box is 5'- HTTAAD N5 HTTAAD. Additionally, we provide the first structural information for the A. baumannii PmrA N-terminal domain through X-ray crystallography, and we present a full-length model using molecular modeling. From these studies, we were able to infer the effects of two critical PmrA mutations, PmrA::I13M and PmrA::P102R, both of which confer increased colistin resistance. Based on these data, we suggest structural and dynamic reasons for how these mutations can affect PmrA function and hence encourage resistive traits. Understanding these mechanisms will aid in the development of new targeted antimicrobial therapies.
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Affiliation(s)
- Samantha Palethorpe
- Department of Microbiology and Immunology Brody School of Medicine East Carolina University Greenville, NC 27834 United States
| | - Morgan E Milton
- Department of Biochemistry and Molecular Biology Brody School of Medicine East Carolina University Greenville, NC 27834 United States
| | - Everett C Pesci
- Department of Microbiology and Immunology Brody School of Medicine East Carolina University Greenville, NC 27834 United States
| | - John Cavanagh
- Department of Biochemistry and Molecular Biology Brody School of Medicine East Carolina University Greenville, NC 27834 United States
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22
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Teixeira RD, Holzschuh F, Schirmer T. Activation mechanism of a small prototypic Rec-GGDEF diguanylate cyclase. Nat Commun 2021; 12:2162. [PMID: 33846343 PMCID: PMC8041772 DOI: 10.1038/s41467-021-22492-7] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2020] [Accepted: 03/15/2021] [Indexed: 01/24/2023] Open
Abstract
Diguanylate cyclases synthesising the bacterial second messenger c-di-GMP are found to be regulated by a variety of sensory input domains that control the activity of their catalytical GGDEF domain, but how activation proceeds mechanistically is, apart from a few examples, still largely unknown. As part of two-component systems, they are activated by cognate histidine kinases that phosphorylate their Rec input domains. DgcR from Leptospira biflexa is a constitutively dimeric prototype of this class of diguanylate cyclases. Full-length crystal structures reveal that BeF3- pseudo-phosphorylation induces a relative rotation of two rigid halves in the Rec domain. This is coupled to a reorganisation of the dimeric structure with concomitant switching of the coiled-coil linker to an alternative heptad register. Finally, the activated register allows the two substrate-loaded GGDEF domains, which are linked to the end of the coiled-coil via a localised hinge, to move into a catalytically competent dimeric arrangement. Bioinformatic analyses suggest that the binary register switch mechanism is utilised by many diguanylate cyclases with N-terminal coiled-coil linkers. As part of two-component systems, diguanylate cyclases (DGCs) are activated by phosphorylation. Structural and computational analyses of DgcR, a model DGC, reveal the phosphorylation-induced conformational changes and the activation mechanism likely shared by many DGCs with N-terminal coiled-coil linkers.
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Affiliation(s)
| | - Fabian Holzschuh
- Structural Biology, Biozentrum, University of Basel, Basel, Switzerland
| | - Tilman Schirmer
- Structural Biology, Biozentrum, University of Basel, Basel, Switzerland.
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23
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Antibiofilm and antivirulence efficacy of myrtenol enhances the antibiotic susceptibility of Acinetobacter baumannii. Sci Rep 2020; 10:21975. [PMID: 33319862 PMCID: PMC7738676 DOI: 10.1038/s41598-020-79128-x] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2020] [Accepted: 11/26/2020] [Indexed: 02/07/2023] Open
Abstract
Acinetobacter baumannii (AB) is rising as a human pathogen of critical priority worldwide as it is the leading cause of chronic opportunistic infections in healthcare settings and the condition is ineradicable with antibiotic therapy. AB possesses the ability to form biofilm on abiotic as well as biotic surfaces which plays a major role in its pathogenesis and resistance in clinical settings. Hence, the demand for an alternative therapy to combat the biofilm-associated infections is increasing. The present study explored the antibiofilm potential of myrtenol, a bicyclic monoterpene present in various plants against reference and clinical strains of AB. Myrtenol (200 μg/mL) exhibited a strong antibiofilm activity without exerting any harmful effect on growth and metabolic viability of AB strains. Microscopic analyses confirmed the reduction in the biofilm thickness and surface coverage upon myrtenol treatment. Especially, myrtenol was found to be effective in disrupting the mature biofilms of tested AB strains. Furthermore, myrtenol inhibited the biofilm-associated virulence factors of AB strains such as extracellular polysaccharide, cell surface hydrophobicity, oxidant resistance, swarming and twitching motility. Transcriptional analysis unveiled the suppression of the biofilm-associated genes such as bfmR, csuA/B, bap, ompA, pgaA, pgaC, and katE by myrtenol. Notably, myrtenol improved the susceptibility of AB strains towards conventional antibiotics such as amikacin, ciprofloxacin, gentamicin and trimethoprim. Thus, the present study demonstrates the therapeutic potential of myrtenol against biofilm-associated infections of AB.
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Marr CM, MacDonald U, Trivedi G, Chakravorty S, Russo TA. An Evaluation of BfmR-Regulated Antimicrobial Resistance in the Extensively Drug Resistant (XDR) Acinetobacter baumannii Strain HUMC1. Front Microbiol 2020; 11:595798. [PMID: 33193275 PMCID: PMC7658413 DOI: 10.3389/fmicb.2020.595798] [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: 08/17/2020] [Accepted: 10/06/2020] [Indexed: 11/13/2022] Open
Abstract
Acinetobacter baumannii is a problematic pathogen due to its common expression of extensive drug resistance (XDR) and ability to survive in the healthcare environment. These characteristics are mediated, in part, by the signal transduction system BfmR/BfmS. We previously demonstrated, in antimicrobial sensitive clinical isolates, that BfmR conferred increased resistance to meropenem and polymyxin E. In this study, potential mechanisms were informed, in part, by a prior transcriptome analysis of the antimicrobial sensitive isolate AB307-0294, which identified the porins OprB and aquaporin (Omp33-36, MapA) as plausible mediators for resistance to hydrophilic antimicrobials such as meropenem. Studies were then performed in the XDR isolate HUMC1, since delineating resistance mechanisms in this genomic background would be more translationally relevant. In HUMC1 BfmR likewise increased meropenem and polymyxin E resistance and upregulated gene expression of OprB and aquaporin. However, the comparison of HUMC1 with isogenic mutant constructs demonstrated that neither OprB nor aquaporin affected meropenem resistance; polymyxin E susceptibility was also unaffected. Next, we determined whether BfmR-mediated biofilm production affected either meropenem or polymyxin E susceptibilities. Interestingly, biofilm formation increased resistance to polymyxin E, but had little, if any effect on meropenem activity. Additionally, BfmR mediated meropenem resistance, and perhaps polymyxin E resistance, was due to BfmR regulated factors that do not affect biofilm formation. These findings increase our understanding of the mechanisms by which BfmR mediates intrinsic antimicrobial resistance in a clinically relevant XDR isolate and suggest that the efficacy of different classes of antimicrobials may vary under biofilm inducing conditions.
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Affiliation(s)
- Candace M Marr
- Department of Medicine, University at Buffalo, Buffalo, NY, United States.,Erie County Medical Center, Buffalo, NY, United States
| | - Ulrike MacDonald
- Department of Medicine, University at Buffalo, Buffalo, NY, United States.,Veterans Affairs Western New York Healthcare System, Buffalo, NY, United States
| | - Grishma Trivedi
- Department of Medicine, University at Buffalo, Buffalo, NY, United States.,Veterans Affairs Western New York Healthcare System, Buffalo, NY, United States
| | | | - Thomas A Russo
- Department of Medicine, University at Buffalo, Buffalo, NY, United States.,Veterans Affairs Western New York Healthcare System, Buffalo, NY, United States.,Department of Microbiology and Immunology, University at Buffalo, Buffalo, NY, United States.,Witebsky Center for Microbial Pathogenesis, University at Buffalo, Buffalo, NY, United States
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Proteomic and Systematic Functional Profiling Unveils Citral Targeting Antibiotic Resistance, Antioxidant Defense, and Biofilm-Associated Two-Component Systems of Acinetobacter baumannii To Encumber Biofilm and Virulence Traits. mSystems 2020; 5:5/6/e00986-20. [PMID: 33203690 PMCID: PMC7677002 DOI: 10.1128/msystems.00986-20] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Acinetobacter baumannii is a nosocomial-infection-causing bacterium and also possesses multidrug resistance to a wide range of conventional antibiotics. The biofilm-forming ability of A. baumannii plays a major role in its resistance and persistence. There is an alarming need for novel treatment strategies to control A. baumannii biofilm-associated issues. The present study demonstrated the strong antibiofilm and antivirulence efficacy of citral against A. baumannii. In addition, proteomic analysis revealed the multitarget potential of citral against A. baumannii. Furthermore, citral treatment enhances the susceptibility of A. baumannii to the host innate immune system and reactive oxygen species (ROS). Cytotoxicity analysis revealed the nonfatal effect of citral on human PBMCs. Therefore, citral could be the safest therapeutic compound and can be taken for further clinical evaluation for the treatment of biofilm-associated infections by A. baumannii. Acinetobacter baumannii has been reported as a multidrug-resistant bacterium due to biofilms and antimicrobial resistance mechanisms. Hence, novel therapeutic strategies are necessary to overcome A. baumannii infections. This study revealed that citral at 200 μg/ml attenuated A. baumannii biofilms by up to 90% without affecting viability. Furthermore, microscopic analyses and in vitro assays confirmed the antibiofilm efficacy of citral. The global effect of citral on A. baumannii was evaluated by proteomic, transcriptional, and in silico approaches. Two-dimensional (2D) gel electrophoresis and matrix-assisted laser desorption ionization–time of flight/time of flight (MALDI-TOF/TOF) analyses were used to assess the effect of citral on the A. baumannii cellular proteome. Quantitative real-time PCR (qPCR) analysis was done to validate the proteomic data and identify the differentially expressed A. baumannii genes. Protein-protein interactions, gene enrichment, and comparative gene network analyses were performed to explore the interactions and functional attributes of differentially expressed proteins of A. baumannii. Global omics-based analyses revealed that citral targeted various mechanisms such as biofilm formation, antibiotic resistance, antioxidant defense, iron acquisition, and type II and type IV secretion systems. The results of antioxidant analyses and antibiotic sensitivity, blood survival, lipase, and hemolysis assays validated the proteomic results. Cytotoxicity analysis showed a nontoxic effect of citral on peripheral blood mononuclear cells (PBMCs). Overall, the current study unveiled that citral has multitarget efficacy to inhibit the biofilm formation and virulence of A. baumannii. IMPORTANCEAcinetobacter baumannii is a nosocomial-infection-causing bacterium and also possesses multidrug resistance to a wide range of conventional antibiotics. The biofilm-forming ability of A. baumannii plays a major role in its resistance and persistence. There is an alarming need for novel treatment strategies to control A. baumannii biofilm-associated issues. The present study demonstrated the strong antibiofilm and antivirulence efficacy of citral against A. baumannii. In addition, proteomic analysis revealed the multitarget potential of citral against A. baumannii. Furthermore, citral treatment enhances the susceptibility of A. baumannii to the host innate immune system and reactive oxygen species (ROS). Cytotoxicity analysis revealed the nonfatal effect of citral on human PBMCs. Therefore, citral could be the safest therapeutic compound and can be taken for further clinical evaluation for the treatment of biofilm-associated infections by A. baumannii.
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CsrA Supports both Environmental Persistence and Host-Associated Growth of Acinetobacter baumannii. Infect Immun 2020; 88:IAI.00259-20. [PMID: 32989034 DOI: 10.1128/iai.00259-20] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2020] [Accepted: 09/18/2020] [Indexed: 11/20/2022] Open
Abstract
Acinetobacter baumannii is an opportunistic and frequently multidrug-resistant Gram-negative bacterial pathogen that primarily infects critically ill individuals. Indirect transmission from patient to patient in hospitals can drive infections, supported by this organism's abilities to persist on dry surfaces and rapidly colonize susceptible individuals. To investigate how A. baumannii survives on surfaces, we cultured A. baumannii in liquid media for several days and then analyzed isolates that lost the ability to survive drying. One of these isolates carried a mutation that affected the gene encoding the carbon storage regulator CsrA. As we began to examine the role of CsrA in A. baumannii, we observed that the growth of ΔcsrA mutant strains was inhibited in the presence of amino acids. The ΔcsrA mutant strains had a reduced ability to survive drying and to form biofilms but an improved ability to tolerate increased osmolarity compared with the wild type. We also examined the importance of CsrA for A. baumannii virulence. The ΔcsrA mutant strains had a greatly reduced ability to kill Galleria mellonella larvae, could not replicate in G. mellonella hemolymph, and also had a growth defect in human serum. Together, these results show that CsrA is essential for the growth of A. baumannii on host-derived substrates and is involved in desiccation tolerance, implying that CsrA controls key functions involved in the transmission of A. baumannii in hospitals.
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Alam P, Alqahtani AS, Mabood Husain F, Tabish Rehman M, Alajmi MF, Noman OM, El Gamal AA, Al-Massarani SM, Shavez Khan M. Siphonocholin isolated from red sea sponge Siphonochalina siphonella attenuates quorum sensing controlled virulence and biofilm formation. Saudi Pharm J 2020; 28:1383-1391. [PMID: 33250645 PMCID: PMC7679466 DOI: 10.1016/j.jsps.2020.09.002] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2020] [Accepted: 09/07/2020] [Indexed: 01/25/2023] Open
Abstract
Increasing incidence of multi-drug resistant bacterial pathogens, especially in clinical settings, has been developed into a grave health situation. The drug resistance problem demands the necessity for alternative unique therapeutic policies. One such tactic is targeting the quorum sensing (QS) controlled virulence and biofilm production. In this study, we evaluated a marine steroid Siphonocholin (Syph-1) isolated from Siphonochalina siphonella against Chromobacterium violaceum (CV) 12472, Pseudomonas aeruginosa (PAO1), Methicillin-resistant Staphylococcus aureus (MRSA) and Acinetobacter baumannii (BAA) for biofilm and pellicle formation inhibition, and anti-QS property. MIC of Syph-1 against MRSA, CV, PAO1 was found as 64 µg/mL and 256 µg/mL against BAA. At selected sub-MICs, Syph-1 significantly (P ≤ 0.05) decreased the production of QS regulated virulence functions of CV12472 (violacein) and PAO1 [elastase, total protease, pyocyanin, chitinase, exopolysaccharides, and swarming motility]. The Syph-1 significantly decreased (p = 0.005) biofilm formation ability of tested bacterial pathogens, at sub-MIC level (PAO1 > MRSA > CV > BAA) and pellicle formation in A. baumannii (at 128 µg/mL). Molecular docking and simulation results indicated that Siph-1 was bound at the active site of BfmR N-terminal domain with high affinity. This study highlights the anti-QS and anti-biofilm activity of Syph-1 against bacterial pathogens reflecting its broad spectrum anti-infective potential.
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Affiliation(s)
- Perwez Alam
- Department of Pharmacognosy, College of Pharmacy, King Saud University, Riyadh, Saudi Arabia
| | - Ali S Alqahtani
- Department of Pharmacognosy, College of Pharmacy, King Saud University, Riyadh, Saudi Arabia
| | - Fohad Mabood Husain
- Department of Food Science and Nutrition, College of Food and Agriculture Sciences, King Saud University, Riyadh, Saudi Arabia
| | - Md Tabish Rehman
- Department of Pharmacognosy, College of Pharmacy, King Saud University, Riyadh, Saudi Arabia
| | - Mohamed F Alajmi
- Department of Pharmacognosy, College of Pharmacy, King Saud University, Riyadh, Saudi Arabia
| | - Omar M Noman
- Department of Pharmacognosy, College of Pharmacy, King Saud University, Riyadh, Saudi Arabia
| | - Ali A El Gamal
- Department of Pharmacognosy, College of Pharmacy, King Saud University, Riyadh, Saudi Arabia
| | - Shaza M Al-Massarani
- Department of Pharmacognosy, College of Pharmacy, King Saud University, Riyadh, Saudi Arabia
| | - Mohammad Shavez Khan
- National Bureau of Agriculturally Important Microorganisms, Maunath Bhanjan, India
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Chen SK, Guan HH, Wu PH, Lin LT, Wu MC, Chang HY, Chen NC, Lin CC, Chuankhayan P, Huang YC, Lin PJ, Chen CJ. Structural insights into the histidine-containing phospho-transfer protein and receiver domain of sensor histidine kinase suggest a complex model in the two-component regulatory system in Pseudomonas aeruginosa. IUCRJ 2020; 7:934-948. [PMID: 32939285 PMCID: PMC7467158 DOI: 10.1107/s2052252520009665] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/05/2020] [Accepted: 07/15/2020] [Indexed: 06/11/2023]
Abstract
In Pseudomonas aeruginosa, an important opportunistic pathogen that causes numerous acute and chronic infections, the hybrid two-component system (TCS) regulates the swarming ability and biofilm formation with a multistep phospho-relay, and consists of hybrid-sensor histidine kinase (HK), histidine-containing phospho-transfer protein (Hpt) and response regulator (RR). In this work, two crystal structures of HptB and the receiver domain of HK PA1611 (PA1611REC) of P. aeruginosa have been determined in order to elucidate their interactions for the transfer of the phospho-ryl group. The structure of HptB folds into an elongated four-helix bundle - helices α2, α3, α4 and α5, covered by the short N-terminal helix α1. The imidazole side chain of the conserved active-site histidine residue His57, located near the middle of helix α3, protrudes from the bundle and is exposed to solvent. The structure of PA1611REC possesses a conventional (β/α)5 topology with five-stranded parallel β-sheets folded in the central region, surrounded by five α-helices. The divalent Mg2+ ion is located in the negatively charged active-site cleft and interacts with Asp522, Asp565 and Arg567. The HptB-PA1611REC complex is further modeled to analyze the binding surface and interactions between the two proteins. The model shows a shape complementarity between the convex surface of PA1611REC and the kidney-shaped HptB with fewer residues and a different network involved in interactions compared with other TCS complexes, such as SLN1-R1/YPD1 from Saccharomyces cerevisiae and AHK5RD/AHP1 from Arabidopsis thaliana. These structural results provide a better understanding of the TCS in P. aeruginosa and could potentially lead to the discovery of a new treatment for infection.
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Affiliation(s)
- Shao-Kang Chen
- Department of Biotechnology and Bioindustry Sciences, National Cheng Kung University, Tainan City 701, Taiwan
- Life Science Group, Scientific Research Division, National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan
| | - Hong-Hsiang Guan
- Life Science Group, Scientific Research Division, National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan
| | - Pei-Hsun Wu
- Life Science Group, Scientific Research Division, National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan
| | - Li-Ting Lin
- Life Science Group, Scientific Research Division, National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan
| | - Meng-Chun Wu
- Department of Biotechnology and Bioindustry Sciences, National Cheng Kung University, Tainan City 701, Taiwan
- Life Science Group, Scientific Research Division, National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan
| | - Hwan-You Chang
- Institute of Molecular Medicine, National Tsing Hua University, Hsinchu 30013, Taiwan
| | - Nai-Chi Chen
- Life Science Group, Scientific Research Division, National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan
| | - Chien-Chih Lin
- Life Science Group, Scientific Research Division, National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan
| | - Phimonphan Chuankhayan
- Life Science Group, Scientific Research Division, National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan
| | - Yen-Chieh Huang
- Life Science Group, Scientific Research Division, National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan
| | - Pei-Ju Lin
- Life Science Group, Scientific Research Division, National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan
- Institute of Bioinformatics and Structural Biology, National Tsing Hua University, Hsinchu 30013, Taiwan
| | - Chun-Jung Chen
- Department of Biotechnology and Bioindustry Sciences, National Cheng Kung University, Tainan City 701, Taiwan
- Life Science Group, Scientific Research Division, National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan
- Department of Physics, National Tsing Hua University, Hsinchu 30013, Taiwan
- Department of Biological Science and Technology, National Chiao Tung University, Hsinchu 30010, Taiwan
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29
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Walsh BJC, Wang J, Edmonds KA, Palmer LD, Zhang Y, Trinidad JC, Skaar EP, Giedroc DP. The Response of Acinetobacter baumannii to Hydrogen Sulfide Reveals Two Independent Persulfide-Sensing Systems and a Connection to Biofilm Regulation. mBio 2020; 11:e01254-20. [PMID: 32576676 PMCID: PMC7315123 DOI: 10.1128/mbio.01254-20] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2020] [Accepted: 05/19/2020] [Indexed: 12/13/2022] Open
Abstract
Acinetobacter baumannii is an opportunistic nosocomial pathogen that is the causative agent of several serious infections in humans, including pneumonia, sepsis, and wound and burn infections. A. baumannii is also capable of forming proteinaceous biofilms on both abiotic and epithelial cell surfaces. Here, we investigate the response of A. baumannii toward sodium sulfide (Na2S), known to be associated with some biofilms at oxic/anoxic interfaces. The addition of exogenous inorganic sulfide reveals that A. baumannii encodes two persulfide-sensing transcriptional regulators, a primary σ54-dependent transcriptional activator (FisR), and a secondary system controlled by the persulfide-sensing biofilm growth-associated repressor (BigR), which is only induced by sulfide in a fisR deletion strain. FisR activates an operon encoding a sulfide oxidation/detoxification system similar to that characterized previously in Staphylococcus aureus, while BigR regulates a secondary persulfide dioxygenase (PDO2) as part of yeeE-yedE-pdo2 sulfur detoxification operon, found previously in Serratia spp. Global S-sulfuration (persulfidation) mapping of the soluble proteome reveals 513 persulfidation targets well beyond FisR-regulated genes and includes five transcriptional regulators, most notably the master biofilm regulator BfmR and a poorly characterized catabolite regulatory protein (Crp). Both BfmR and Crp are well known to impact biofilm formation in A. baumannii and other organisms, respectively, suggesting that persulfidation of these regulators may control their activities. The implications of these findings on bacterial sulfide homeostasis, persulfide signaling, and biofilm formation are discussed.IMPORTANCE Although hydrogen sulfide (H2S) has long been known as a respiratory poison, recent reports in numerous bacterial pathogens reveal that H2S and more downstream oxidized forms of sulfur collectedly termed reactive sulfur species (RSS) function as antioxidants to combat host efforts to clear the infection. Here, we present a comprehensive analysis of the transcriptional and proteomic response of A. baumannii to exogenous sulfide as a model for how this important human pathogen manages sulfide/RSS homeostasis. We show that A. baumannii is unique in that it encodes two independent persulfide sensing and detoxification pathways that govern the speciation of bioactive sulfur in cells. The secondary persulfide sensor, BigR, impacts the expression of biofilm-associated genes; in addition, we identify two other transcriptional regulators known or projected to regulate biofilm formation, BfmR and Crp, as highly persulfidated in sulfide-exposed cells. These findings significantly strengthen the connection between sulfide homeostasis and biofilm formation in an important human pathogen.
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Affiliation(s)
- Brenna J C Walsh
- Department of Chemistry, Indiana University, Bloomington, Indiana, USA
| | - Jiefei Wang
- Department of Chemistry, Indiana University, Bloomington, Indiana, USA
- Department of Molecular and Cellular Biochemistry, Indiana University, Bloomington, Indiana, USA
| | | | - Lauren D Palmer
- Department of Pathology, Microbiology and Immunology, and Vanderbilt Institute for Infection, Immunology and Inflammation, Vanderbilt University Medical Center, Nashville, Tennessee, USA
| | - Yixiang Zhang
- Laboratory for Biological Mass Spectrometry, Indiana University, Bloomington, Indiana, USA
| | - Jonathan C Trinidad
- Laboratory for Biological Mass Spectrometry, Indiana University, Bloomington, Indiana, USA
| | - Eric P Skaar
- Department of Pathology, Microbiology and Immunology, and Vanderbilt Institute for Infection, Immunology and Inflammation, Vanderbilt University Medical Center, Nashville, Tennessee, USA
| | - David P Giedroc
- Department of Chemistry, Indiana University, Bloomington, Indiana, USA
- Department of Molecular and Cellular Biochemistry, Indiana University, Bloomington, Indiana, USA
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30
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Metal-induced sensor mobilization turns on affinity to activate regulator for metal detoxification in live bacteria. Proc Natl Acad Sci U S A 2020; 117:13248-13255. [PMID: 32467170 DOI: 10.1073/pnas.1919816117] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Metal detoxification is essential for bacteria's survival in adverse environments and their pathogenesis in hosts. Understanding the underlying mechanisms is crucial for devising antibacterial treatments. In the Gram-negative bacterium Escherichia coli, membrane-bound sensor CusS and its response regulator CusR together regulate the transcription of the cus operon that plays important roles in cells' resistance to copper/silver, and they belong to the two-component systems (TCSs) that are ubiquitous across various organisms and regulate diverse cellular functions. In vitro protein reconstitution and associated biochemical/physical studies have provided significant insights into the functions and mechanisms of CusS-CusR and related TCSs. Such studies are challenging regarding multidomain membrane proteins like CusS and also lack the physiological environment, particularly the native spatial context of proteins inside a cell. Here, we use stroboscopic single-molecule imaging and tracking to probe the dynamic behaviors of both CusS and CusR in live cells, in combination with protein- or residue-specific genetic manipulations. We find that copper stress leads to a cellular protein concentration increase and a concurrent mobilization of CusS out of clustered states in the membrane. We show that the mobilized CusS has significant interactions with CusR for signal transduction and that CusS's affinity toward CusR switches on upon sensing copper at the interfacial metal-binding sites in CusS's periplasmic sensor domains, prior to ATP binding and autophosphorylation at CusS's cytoplasmic kinase domain(s). The observed CusS mobilization upon stimulation and its surprisingly early interaction with CusR likely ensure an efficient signal transduction by providing proper conformation and avoiding futile cross talks.
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31
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Dean SN, Milton ME, Cavanagh J, van Hoek ML. Francisella novicida Two-Component System Response Regulator BfpR Modulates iglC Gene Expression, Antimicrobial Peptide Resistance, and Biofilm Production. Front Cell Infect Microbiol 2020; 10:82. [PMID: 32232010 PMCID: PMC7082314 DOI: 10.3389/fcimb.2020.00082] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2019] [Accepted: 02/18/2020] [Indexed: 12/20/2022] Open
Abstract
Response regulators are a critical part of the two-component system of gene expression regulation in bacteria, transferring a signal from a sensor kinase into DNA binding activity resulting in alteration of gene expression. In this study, we investigated a previously uncharacterized response regulator in Francisella novicida, FTN_1452 that we have named BfpR (Biofilm-regulating Francisella protein Regulator, FTN_1452). In contrast to another Francisella response regulator, QseB/PmrA, BfpR appears to be a negative regulator of biofilm production, and also a positive regulator of antimicrobial peptide resistance in this bacterium. The protein was crystallized and X-ray crystallography studies produced a 1.8 Å structure of the BfpR N-terminal receiver domain revealing interesting insight into its potential interaction with the sensor kinase. Structural analysis of BfpR places it in the OmpR/PhoP family of bacterial response regulators along with WalR and ResD. Proteomic and transcriptomic analyses suggest that BfpR overexpression affects expression of the critical Francisella virulence factor iglC, as well as other proteins in the bacterium. We demonstrate that mutation of bfpR is associated with an antimicrobial peptide resistance phenotype, a phenotype also associated with other response regulators, for the human cathelicidin peptide LL-37 and a sheep antimicrobial peptide SMAP-29. F. novicida with mutated bfpR replicated better than WT in intracellular infection assays in human-derived macrophages suggesting that the down-regulation of iglC expression in bfpR mutant may enable this intracellular replication to occur. Response regulators have been shown to play important roles in the regulation of bacterial biofilm production. We demonstrate that F. novicida biofilm formation was highly increased in the bfpR mutant, corresponding to altered glycogen synthesis. Waxworm infection experiments suggest a role of BfpR as a negative modulator of iglC expression with de-repression by Mg2+. In this study, we find that the response regulator BfpR may be a negative regulator of biofilm formation, and a positive regulator of antimicrobial peptide resistance in F. novicida.
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Affiliation(s)
- Scott N Dean
- National Center for Biodefense and Infectious Diseases, and School of Systems Biology, George Mason University, Manassas, VA, United States
| | - Morgan E Milton
- Department of Biochemistry and Molecular Biology, The Brody School of Medicine, East Carolina University, Greenville, NC, United States
| | - John Cavanagh
- Department of Biochemistry and Molecular Biology, The Brody School of Medicine, East Carolina University, Greenville, NC, United States
| | - Monique L van Hoek
- National Center for Biodefense and Infectious Diseases, and School of Systems Biology, George Mason University, Manassas, VA, United States
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Wang S, Denton KE, Hobbs KF, Weaver T, McFarlane JMB, Connelly KE, Gignac MC, Milosevich N, Hof F, Paci I, Musselman CA, Dykhuizen EC, Krusemark CJ. Optimization of Ligands Using Focused DNA-Encoded Libraries To Develop a Selective, Cell-Permeable CBX8 Chromodomain Inhibitor. ACS Chem Biol 2020; 15:112-131. [PMID: 31755685 DOI: 10.1021/acschembio.9b00654] [Citation(s) in RCA: 49] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Polycomb repressive complex 1 (PRC1) is critical for mediating gene expression during development. Five chromobox (CBX) homolog proteins, CBX2, CBX4, CBX6, CBX7, and CBX8, are incorporated into PRC1 complexes, where they mediate targeting to trimethylated lysine 27 of histone H3 (H3K27me3) via the N-terminal chromodomain (ChD). Individual CBX paralogs have been implicated as drug targets in cancer; however, high similarities in sequence and structure among the CBX ChDs provide a major obstacle in developing selective CBX ChD inhibitors. Here we report the selection of small, focused, DNA-encoded libraries (DELs) against multiple homologous ChDs to identify modifications to a parental ligand that confer both selectivity and potency for the ChD of CBX8. This on-DNA, medicinal chemistry approach enabled the development of SW2_110A, a selective, cell-permeable inhibitor of the CBX8 ChD. SW2_110A binds CBX8 ChD with a Kd of 800 nM, with minimal 5-fold selectivity for CBX8 ChD over all other CBX paralogs in vitro. SW2_110A specifically inhibits the association of CBX8 with chromatin in cells and inhibits the proliferation of THP1 leukemia cells driven by the MLL-AF9 translocation. In THP1 cells, SW2_110A treatment results in a significant decrease in the expression of MLL-AF9 target genes, including HOXA9, validating the previously established role for CBX8 in MLL-AF9 transcriptional activation, and defining the ChD as necessary for this function. The success of SW2_110A provides great promise for the development of highly selective and cell-permeable probes for the full CBX family. In addition, the approach taken provides a proof-of-principle demonstration of how DELs can be used iteratively for optimization of both ligand potency and selectivity.
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Affiliation(s)
- Sijie Wang
- Department of Medicinal Chemistry and Molecular Pharmacology, College of Pharmacy, Purdue University and Purdue University Center for Cancer Research, 575 Stadium Mall Drive, West Lafayette, Indiana 47906, United States
| | - Kyle E. Denton
- Department of Medicinal Chemistry and Molecular Pharmacology, College of Pharmacy, Purdue University and Purdue University Center for Cancer Research, 575 Stadium Mall Drive, West Lafayette, Indiana 47906, United States
| | - Kathryn F. Hobbs
- Department of Biochemistry, Carver College of Medicine, University of Iowa, 51 Newton Road, Iowa City, Iowa 52242, United States
| | - Tyler Weaver
- Department of Biochemistry, Carver College of Medicine, University of Iowa, 51 Newton Road, Iowa City, Iowa 52242, United States
| | | | - Katelyn E. Connelly
- Department of Medicinal Chemistry and Molecular Pharmacology, College of Pharmacy, Purdue University and Purdue University Center for Cancer Research, 575 Stadium Mall Drive, West Lafayette, Indiana 47906, United States
| | - Michael C. Gignac
- Department of Chemistry, University of Victoria, Victoria V8W 3V6, Canada
| | - Natalia Milosevich
- Department of Chemistry, University of Victoria, Victoria V8W 3V6, Canada
| | - Fraser Hof
- Department of Chemistry, University of Victoria, Victoria V8W 3V6, Canada
| | - Irina Paci
- Department of Chemistry, University of Victoria, Victoria V8W 3V6, Canada
| | - Catherine A. Musselman
- Department of Biochemistry, Carver College of Medicine, University of Iowa, 51 Newton Road, Iowa City, Iowa 52242, United States
| | - Emily C. Dykhuizen
- Department of Medicinal Chemistry and Molecular Pharmacology, College of Pharmacy, Purdue University and Purdue University Center for Cancer Research, 575 Stadium Mall Drive, West Lafayette, Indiana 47906, United States
| | - Casey J. Krusemark
- Department of Medicinal Chemistry and Molecular Pharmacology, College of Pharmacy, Purdue University and Purdue University Center for Cancer Research, 575 Stadium Mall Drive, West Lafayette, Indiana 47906, United States
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33
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Geisinger E, Huo W, Hernandez-Bird J, Isberg RR. Acinetobacter baumannii: Envelope Determinants That Control Drug Resistance, Virulence, and Surface Variability. Annu Rev Microbiol 2019; 73:481-506. [DOI: 10.1146/annurev-micro-020518-115714] [Citation(s) in RCA: 53] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Acinetobacter baumannii has emerged as an important nosocomial pathogen, particularly for patients in intensive care units and with invasive indwelling devices. The most recent clinical isolates are resistant to several classes of clinically important antibiotics, greatly restricting the ability to effectively treat critically ill patients. The bacterial envelope is an important driver of A. baumannii disease, both at the level of battling against antibiotic therapy and at the level of protecting from host innate immune function. This review provides a comprehensive overview of key features of the envelope that interface with both the host and antimicrobial therapies. Carbohydrate structures that contribute to protecting from the host are detailed, and mutations that alter these structures, resulting in increased antimicrobial resistance, are explored. In addition, protein complexes involved in both intermicrobial and host-microbe interactions are described. Finally we discuss regulatory mechanisms that control the nature of the cell envelope and its impact on host innate immune function.
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Affiliation(s)
- Edward Geisinger
- Department of Biology, Northeastern University, Boston, Massachusetts 02115, USA
| | - Wenwen Huo
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, Massachusetts 02111, USA
| | - Juan Hernandez-Bird
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, Massachusetts 02111, USA
| | - Ralph R. Isberg
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, Massachusetts 02111, USA
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Milton ME, Draughn GL, Bobay BG, Stowe SD, Olson AL, Feldmann EA, Thompson RJ, Myers KH, Santoro MT, Kearns DB, Cavanagh J. The Solution Structures and Interaction of SinR and SinI: Elucidating the Mechanism of Action of the Master Regulator Switch for Biofilm Formation in Bacillus subtilis. J Mol Biol 2019; 432:343-357. [PMID: 31493408 DOI: 10.1016/j.jmb.2019.08.019] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2019] [Revised: 08/09/2019] [Accepted: 08/29/2019] [Indexed: 02/04/2023]
Abstract
Bacteria have developed numerous protection strategies to ensure survival in harsh environments, with perhaps the most robust method being the formation of a protective biofilm. In biofilms, bacterial cells are embedded within a matrix that is composed of a complex mixture of polysaccharides, proteins, and DNA. The gram-positive bacterium Bacillus subtilis has become a model organism for studying regulatory networks directing biofilm formation. The phenotypic transition from a planktonic to biofilm state is regulated by the activity of the transcriptional repressor, SinR, and its inactivation by its primary antagonist, SinI. In this work, we present the first full-length structural model of tetrameric SinR using a hybrid approach combining high-resolution solution nuclear magnetic resonance (NMR), chemical cross-linking, mass spectrometry, and molecular docking. We also present the solution NMR structure of the antagonist SinI dimer and probe the mechanism behind the SinR-SinI interaction using a combination of biochemical and biophysical techniques. As a result of these findings, we propose that SinI utilizes a residue replacement mechanism to block SinR multimerization, resulting in diminished DNA binding and concomitant decreased repressor activity. Finally, we provide an evidence-based mechanism that confirms how disruption of the SinR tetramer by SinI regulates gene expression.
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Affiliation(s)
- Morgan E Milton
- Department of Biochemistry and Molecular Biology, The Brody School of Medicine, East Carolina University, Greenville, NC 27834, USA
| | - G Logan Draughn
- Department of Molecular and Structural Biochemistry, North Carolina State University, Raleigh, NC 27695, USA
| | - Benjamin G Bobay
- Department of Molecular and Structural Biochemistry, North Carolina State University, Raleigh, NC 27695, USA; Duke University NMR Center, Duke University, Durham, NC 27710, USA
| | - Sean D Stowe
- Department of Molecular and Structural Biochemistry, North Carolina State University, Raleigh, NC 27695, USA
| | - Andrew L Olson
- Department of Molecular and Structural Biochemistry, North Carolina State University, Raleigh, NC 27695, USA
| | - Erik A Feldmann
- Department of Molecular and Structural Biochemistry, North Carolina State University, Raleigh, NC 27695, USA
| | - Richele J Thompson
- Department of Biochemistry and Molecular Biology, The Brody School of Medicine, East Carolina University, Greenville, NC 27834, USA
| | - Katherine H Myers
- Department of Molecular and Structural Biochemistry, North Carolina State University, Raleigh, NC 27695, USA
| | - Michael T Santoro
- Department of Molecular and Structural Biochemistry, North Carolina State University, Raleigh, NC 27695, USA
| | - Daniel B Kearns
- Department of Biology, Indiana University Bloomington, Bloomington, IN 47405, USA
| | - John Cavanagh
- Department of Biochemistry and Molecular Biology, The Brody School of Medicine, East Carolina University, Greenville, NC 27834, USA.
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Raorane CJ, Lee JH, Kim YG, Rajasekharan SK, García-Contreras R, Lee J. Antibiofilm and Antivirulence Efficacies of Flavonoids and Curcumin Against Acinetobacter baumannii. Front Microbiol 2019; 10:990. [PMID: 31134028 PMCID: PMC6517519 DOI: 10.3389/fmicb.2019.00990] [Citation(s) in RCA: 76] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2018] [Accepted: 04/18/2019] [Indexed: 01/08/2023] Open
Abstract
Acinetobacter baumannii is well adapted to hospital environments, and the persistence of its chronic infections is mainly due to its ability to form biofilms resistant to conventional antibiotics and host immune systems. Hence, the inhibitions of biofilm formation and virulence characteristics provide other means of addressing infections. In this study, the antibiofilm activities of twelve flavonoids were initially investigated. Three most active flavonoids, namely, fisetin, phloretin, and curcumin, dose-dependently inhibited biofilm formation by a reference A. baumannii strain and by several clinical isolates, including four multidrug-resistant isolates. Furthermore, the antibiofilm activity of curcumin (the most active flavonoid) was greater than that of the well-known biofilm inhibitor gallium nitrate. Curcumin inhibited pellicle formation and the surface motility of A. baumannii. Interestingly, curcumin also showed antibiofilm activity against Candida albicans and mixed cultures of C. albicans and A. baumannii. In silico molecular docking of the biofilm response regulator BfmR showed that the binding efficacy of flavonoids with BfmR was correlated with antibiofilm efficacy. In addition, curcumin treatment diminished A. baumannii virulence in an in vivo Caenorhabditis elegans model without cytotoxicity. The study shows curcumin and other flavonoids have potential for controlling biofilm formation by and the virulence of A. baumannii.
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Affiliation(s)
| | - Jin-Hyung Lee
- School of Chemical Engineering, Yeungnam University, Gyeongsan, South Korea
| | - Yong-Guy Kim
- School of Chemical Engineering, Yeungnam University, Gyeongsan, South Korea
| | | | - Rodolfo García-Contreras
- Department of Microbiology and Parasitology, Faculty of Medicine, National Autonomous University of Mexico, Mexico City, Mexico
| | - Jintae Lee
- School of Chemical Engineering, Yeungnam University, Gyeongsan, South Korea
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De Silva PM, Kumar A. Signal Transduction Proteins in Acinetobacter baumannii: Role in Antibiotic Resistance, Virulence, and Potential as Drug Targets. Front Microbiol 2019; 10:49. [PMID: 30761101 PMCID: PMC6363711 DOI: 10.3389/fmicb.2019.00049] [Citation(s) in RCA: 38] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2018] [Accepted: 01/14/2019] [Indexed: 12/16/2022] Open
Abstract
Acinetobacter baumannii is a notorious pathogen in health care settings around the world, primarily due to high resistance to antibiotics. A. baumannii also shows an impressive capability to adapt to harsh conditions in clinical settings, which contributes to its persistence in such conditions. Following their traditional role, the Two Component Systems (TCSs) present in A. baumannii play a crucial role in sensing and adapting to the changing environmental conditions. This provides A. baumannii with a greater chance of survival even in unfavorable conditions. Since all the TCSs characterized to date in A. baumannii play a role in its antibiotic resistance and virulence, understanding the underlying molecular mechanisms behind TCSs can help with a better understanding of the pathways that regulate these phenotypes. This can also guide efforts to target TCSs as novel drug targets. In this review, we discuss the roles of TCSs in A. baumannii, their molecular mechanisms, and most importantly, the potential of using small molecule inhibitors of TCSs as potential novel drug targets.
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Affiliation(s)
- P Malaka De Silva
- Department of Microbiology, University of Manitoba, Winnipeg, MB, Canada
| | - Ayush Kumar
- Department of Microbiology, University of Manitoba, Winnipeg, MB, Canada.,Manitoba Chemosensory Biology Group, University of Manitoba, Winnipeg, MB, Canada
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Farrow JM, Wells G, Pesci EC. Desiccation tolerance in Acinetobacter baumannii is mediated by the two-component response regulator BfmR. PLoS One 2018; 13:e0205638. [PMID: 30308034 PMCID: PMC6181384 DOI: 10.1371/journal.pone.0205638] [Citation(s) in RCA: 55] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2018] [Accepted: 09/28/2018] [Indexed: 12/03/2022] Open
Abstract
For the opportunistic pathogen Acinetobacter baumannii, desiccation tolerance is thought to contribute significantly to the persistence of these bacteria in the healthcare environment. We investigated the ability of A. baumannii to survive rapid drying, and found that some strains exhibited a profoundly desiccation-resistant phenotype, characterized by the ability of a large proportion of cells to survive on a dry surface for an extended period of time. However, this phenotype was only displayed during the stationary phase of growth. Most interestingly, we found that drying resistance could be lost after extended cultivation in liquid medium. Genome sequencing of isolates that became drying-sensitive identified mutations in bfmR, which encodes a two-component response regulator that is important for A. baumannii virulence. Additionally, BfmR was necessary for the expression of stress-related proteins during stationary phase, and one of these, KatE, was important for long-term drying survival. These results suggested that BfmR may control stress responses, and we demonstrated that the ΔbfmR mutant was more sensitive to hydrogen peroxide, nutrient starvation, and increased osmolarity. We also found that cross-protection against drying could be stimulated by either starvation, which required BfmR, or increased osmolarity. These results imply that BfmR plays a role in controlling stress responses in A. baumannii which help protect cells during desiccation, and they provide a regulatory link between this organism’s ability to persist in the environment and pathogenicity.
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Affiliation(s)
- John M. Farrow
- Department of Microbiology and Immunology, The Brody School of Medicine at East Carolina University, Greenville, North Carolina, United States of America
| | - Greg Wells
- Department of Microbiology and Immunology, The Brody School of Medicine at East Carolina University, Greenville, North Carolina, United States of America
| | - Everett C. Pesci
- Department of Microbiology and Immunology, The Brody School of Medicine at East Carolina University, Greenville, North Carolina, United States of America
- * E-mail:
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