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Dey R, Valle DO, Chakraborty A, Mayer KA, Uppala JK, Chakraborty A, Mirza S, Skwor T, Forst S, Dey M. Quorum sensing regulators and non-ribosomal peptide synthetases govern antibacterial secretions in Xenorhabdus szentirmaii. Front Microbiol 2025; 16:1560663. [PMID: 40143860 PMCID: PMC11936946 DOI: 10.3389/fmicb.2025.1560663] [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: 01/14/2025] [Accepted: 02/10/2025] [Indexed: 03/28/2025] Open
Abstract
The decades-long gap in antibiotic discovery has led to a significant health crisis due to antimicrobial resistance (AMR). The bacterial genus Xenorhabdus, which forms symbiotic relationships with the soil nematode Steinernema, are known to secrete a variety of antimicrobial compounds with potential effectiveness against AMR. These antimicrobial compounds are primarily bio-synthesized by non-ribosomal peptide synthetases (NRPS) and polyketide synthase (PKS) genes. In this study, we report that X. szentirmaii produces high levels of antibiotic activity during the stationary phase against diverse bacteria including known antibiotic resistant pathogens. It possesses 17 operons to encode predicted NRPS and PKS enzymes, designated as ste1 through ste17. The ste15-ste16 and ste17 operons are predicted to produce the known antibiotics Pax peptide and Fabclavine, respectively. Additionally, the newly identified operons ste3, ste4, ste5, ste8, ste9, and ste14 consist of single genes, each containing two or more NRPS genes. The ste13 operon harbors two NRPS genes, while the ste7 and ste12 operons contain three NRPS genes each. Further, RNA-seq analysis showed that lsrF that encodes a quorum sensing autoinducer-2 (AI-2) thiolase was expressed at high levels during stationary phase. These findings provide evidence that X. szentirmaii uses quorum sensing (QS) to synchronize the expression of multiple NRPS and PKS enzymes responsible for synthesizing various antimicrobial compounds. This study underscores the potential to leverage these regulatory insights for maximizing commercial applications of novel antibiotics combating AMR, as well as broader industrial uses.
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Affiliation(s)
- Ritisha Dey
- Department of Biological Sciences, University of Wisconsin-Milwaukee, Milwaukee, WI, United States
| | - Domonique Olivia Valle
- Department of Biological Sciences, University of Wisconsin-Milwaukee, Milwaukee, WI, United States
| | - Abhijit Chakraborty
- Center for Cancer Immunotherapy, La Jolla Institute for Immunology, La Jolla, CA, United States
| | - Kimberly A. Mayer
- Department of Biological Sciences, University of Wisconsin-Milwaukee, Milwaukee, WI, United States
| | - Jagadeesh Kumar Uppala
- Department of Biological Sciences, University of Wisconsin-Milwaukee, Milwaukee, WI, United States
| | - Anish Chakraborty
- Department of Biological Sciences, University of Wisconsin-Milwaukee, Milwaukee, WI, United States
| | - Shama Mirza
- Department of Chemistry and Biochemistry, University of Wisconsin-Milwaukee, Milwaukee, WI, United States
| | - Troy Skwor
- Department of Biomedical Sciences, University of Wisconsin-Milwaukee, Milwaukee, WI, United States
| | - Steven Forst
- Department of Biological Sciences, University of Wisconsin-Milwaukee, Milwaukee, WI, United States
| | - Madhusudan Dey
- Department of Biological Sciences, University of Wisconsin-Milwaukee, Milwaukee, WI, United States
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Li D, Huo C, Li G, Zhu M, Xu F, Qiao J, Sun H. The absence of luxS reduces the invasion of Avibacterium paragallinarum but is not essential for virulence. Front Vet Sci 2024; 11:1427966. [PMID: 39263678 PMCID: PMC11390136 DOI: 10.3389/fvets.2024.1427966] [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: 05/05/2024] [Accepted: 07/18/2024] [Indexed: 09/13/2024] Open
Abstract
The contagious respiratory pathogen, Avibacterium paragallinarum, contributes to infectious coryza in poultry. However, commercial vaccines have not shown perfect protection against infectious coryza. To search for an alternative approach, this research aimed to investigate whether the quorum-sensing system of pathogens plays a crucial role in their survival and pathogenicity. The LuxS/AI-2 quorum-sensing system in many Gram-negative and Gram-positive bacteria senses environmental changes to regulate physiological traits and virulent properties, and the role of the luxS gene in Av. paragallinarum remains unclear. To investigate the effect of the luxS gene in the quorum-sensing system of Av. paragallinarum, we constructed a luxS mutant. Bioluminescence analysis indicated that the luxS gene plays a vital role in the LuxS/AI-2 quorum-sensing system. The analysis of the LuxS/AI-2 system-related genes showed the level of pfs mRNA to be significantly increased in the mutant strain; however, lsrR, lsrK, and lsrB mRNA levels were not significantly different compared with the wild type. The ability of the luxS mutant strain to invade HD11 and DF-1 cells was significantly decreased compared with the wild-type strain. In addition, all chickens challenged with various doses of the luxS mutant strain developed infections and symptoms, and those challenged with the lowest dose exhibited only minor differences compared to chickens challenged with the wild-type strain. Thus, the deletion of the luxS gene reduces the invasion, but the luxS gene does not play an essential role in the pathogenesis of A. paragallinarum.
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Affiliation(s)
- Donghai Li
- Department of Pathophysiology, College of Veterinary Medicine, China Agricultural University, Beijing, China
- Beijing Key Laboratory for Prevention and Control of Infectious Diseases in Livestock and Poultry, Institute of Animal Husbandry and Veterinary Medicine, Beijing Academy of Agriculture and Forestry Sciences, Beijing, China
| | - Caiyun Huo
- Beijing Key Laboratory for Prevention and Control of Infectious Diseases in Livestock and Poultry, Institute of Animal Husbandry and Veterinary Medicine, Beijing Academy of Agriculture and Forestry Sciences, Beijing, China
| | - Guiping Li
- Beijing Key Laboratory for Prevention and Control of Infectious Diseases in Livestock and Poultry, Institute of Animal Husbandry and Veterinary Medicine, Beijing Academy of Agriculture and Forestry Sciences, Beijing, China
| | - Menghan Zhu
- Beijing Key Laboratory for Prevention and Control of Infectious Diseases in Livestock and Poultry, Institute of Animal Husbandry and Veterinary Medicine, Beijing Academy of Agriculture and Forestry Sciences, Beijing, China
| | - Fuzhou Xu
- Beijing Key Laboratory for Prevention and Control of Infectious Diseases in Livestock and Poultry, Institute of Animal Husbandry and Veterinary Medicine, Beijing Academy of Agriculture and Forestry Sciences, Beijing, China
| | - Jian Qiao
- Department of Pathophysiology, College of Veterinary Medicine, China Agricultural University, Beijing, China
| | - Huiling Sun
- Beijing Key Laboratory for Prevention and Control of Infectious Diseases in Livestock and Poultry, Institute of Animal Husbandry and Veterinary Medicine, Beijing Academy of Agriculture and Forestry Sciences, Beijing, China
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Zhang W, He M, Kong N, Niu Y, Li A, Yan Y. Study on the inhibition activity and mechanism of Tanreqing against Klebsiella pneumoniae biofilm formation in vitro and in vivo. Front Cell Infect Microbiol 2024; 14:1368450. [PMID: 38638833 PMCID: PMC11024231 DOI: 10.3389/fcimb.2024.1368450] [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: 01/10/2024] [Accepted: 03/21/2024] [Indexed: 04/20/2024] Open
Abstract
Objective To evaluate the antibacterial effect of Tanreqing (TRQ) against K. pneumoniae and its inhibition activity on bacterial biofilm formation in vitro and in vivo, and to explore the mechanism of the inhibitory effects of TRQ on K. pneumoniae biofilm formation. Methods An in vitro biofilm model of K. pneumoniae was established, and the impact of TRQ on biofilm formation was evaluated using crystal violet staining and scanning electron microscopy (SEM). Furthermore, the clearance effect of TRQ against K. pneumoniae in the biofilm was assessed using the viable plate counting method; q-RT PCR was used to evaluate the inhibitory effect of different concentrations of TRQ on the expression of biofilm-related genes in Klebsiella pneumoniae; The activity of quorum sensing signal molecule AI-2 was detected by Vibrio harveyi bioluminescence assay; Meanwhile, a guinea pig lung infection model of Klebsiella pneumoniae was constructed, and after treated with drugs, pathological analysis of lung tissue and determination of bacterial load in lung tissue were performed. The treatment groups included TRQ group, imipenem(IPM) group, TRQ+IPM group, and sterile saline group as the control. Results The formation of K. pneumoniae biofilm was significantly inhibited by TRQ in vitro experiments. Furthermore, when combined with IPM, the clearance of K. pneumoniae in the biofilm was notably increased compared to the TRQ group and IPM group alone. q-RT PCR analysis revealed that TRQ down-regulated the expression of genes related to biofilm formation in K. pneumoniae, specifically luxS, wbbm, wzm, and lsrK, and also inhibited the activity of AI-2 molecules in the bacterium. In vivo experiments demonstrated that TRQ effectively treated guinea pig lung infections, resulting in reduced lung inflammation. Additionally, when combined with IPM, there was a significant reduction in the bacterial load in lung tissue. Conclusion TRQ as a potential therapeutic agent plays a great role in the treatment of K. pneumoniae infections, particularly in combination with conventional antibiotics. And TRQ can enhanced the clearance effect on the bacterium by inhibiting the K. pneumoniae biofilm formation, which provided experimental evidence in support of clinical treatment of TRQ against K. pneumoniae infections.
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Affiliation(s)
- Wenxia Zhang
- Department of Laboratory Medicine, Zhoupu Hospital, Shanghai University of Medicine & Health Sciences, Shanghai, China
- Clinical Research Center, Shuguang Hospital, Shanghai University of Traditional Chinese Medicine, Shanghai, China
| | - Min He
- Clinical Research Center, Shuguang Hospital, Shanghai University of Traditional Chinese Medicine, Shanghai, China
| | - Nana Kong
- Department of Clinical Laboratory, Longhua Hospital Affiliated to Shanghai University of Traditional Chinese Medicine, Shanghai, China
| | - Yuxiao Niu
- Xinxiang Medical University, Xinxiang, Henan, China
| | - Anhong Li
- Shanghai University of Traditional Chinese Medicine, Shanghai, China
| | - Yuzhong Yan
- Department of Laboratory Medicine, Zhoupu Hospital, Shanghai University of Medicine & Health Sciences, Shanghai, China
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Shi Q, Wen H, Xu Y, Zhao X, Zhang J, Li Y, Meng Q, Yu F, Xiao J, Li X. Virtual screening-based discovery of AI-2 quorum sensing inhibitors that interact with an allosteric hydrophobic site of LsrK and their functional evaluation. Front Chem 2023; 11:1185224. [PMID: 37292175 PMCID: PMC10244669 DOI: 10.3389/fchem.2023.1185224] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2023] [Accepted: 05/09/2023] [Indexed: 06/10/2023] Open
Abstract
Introduction: Quorum sensing (QS) is a bacterial intracellular and intercellular communication system that regulates virulence factor production, biofilm formation, and antibiotic sensitivity. Quorum-sensing inhibitors (QSIs) are a novel class of antibiotics that can effectively combat antibiotic resistance. Autoinducer-2 (AI-2) is a universal signaling molecule that mediates inter- and intraspecies QS systems among different bacteria. Furthermore, LsrK plays an important role in regulating the activity and stability of the intracellular AI-2 signaling pathway. Thus, LsrK is considered an important target for the development of QSIs. Methods: We designed a workflow integrating molecular dynamic (MD) simulations, virtual screening, LsrK inhibition assays, cell-based AI-2-mediated QS interference assays, and surface plasmon resonance (SPR)-based protein affinity assays to screen for potential LsrK kinase inhibitors. Results: MD simulation results of the LsrK/ATP complex revealed hydrogen bonds and salt bridge formation among four key residues, namely, Lys 431, Tyr 341, Arg 319, and Arg 322, which are critical for the binding of ATP to LsrK. Furthermore, MD simulation results indicated that the ATP-binding site has an allosteric pocket that can become larger and be occupied by small molecule compounds. Based on these MD simulation results, a constraint of forming at least one hydrogen bond with Arg 319, Arg 322, Lys 431, or Tyr 341 residues was introduced when performing virtual screening using Glide's virtual screening workflow (VSW). In the meantime, compounds with hydrophobic group likely to interact with the allosteric hydrophobic pocket are preferred when performing visual inspection. Seventy-four compounds were selected for the wet laboratory assays based on virtual screening and the absorption, distribution, metabolism, and excretion (ADME) properties of these compounds. LsrK inhibition assays revealed 12 compounds inhibiting LsrK by more than 60% at a 200 μM concentration; four of these (Y205-6768, D135-0149, 3284-1358, and N025-0038) had IC50 values below 50 μM and were confirmed as ATP-competitive inhibitors. Six of these 12 LsrK inhibitors exhibited high AI-2 QS inhibition, of which, Y205-6768 had the highest activity with IC50 = 11.28 ± 0.70 μM. The SPR assay verified that compounds Y205-6768 and N025-0038 specifically bound to LsrK. MD simulation analysis of the docking complexes of the four active compounds with LsrK further confirmed the importance of forming hydrogen bonds and salt bridges with key basic amino acid residues including Lys 431, Tyr 341, Arg 319, and Arg 322 and filling the allosteric hydrophobic pocket next to the purine-binding site of LsrK. Discussion: Our study clarified for the first time that there is an allosteric site near the ATP-binding site of Lsrk and that it enriches the structure-activity relationship information of Lsrk inhibitors. The four identified compounds showed novel structures, low molecular weights, high activities, and novel LsrK binding modes, rendering them suitable for further optimization for effective AI-2 QSIs. Our work provides a valuable reference for the discovery of QSIs that do not inhibit bacterial growth, thereby avoiding the emergence of drug resistance.
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Affiliation(s)
- Qianqian Shi
- School of Petrochemical Engineering, Liaoning Petrochemical University, Fushun, China
- National Engineering Research Center for the Emergency Strategic Drug, Beijing Institute of Pharmacology and Toxicology, Beijing, China
| | - Huiqi Wen
- State Key Laboratory of Pathogen and Biosecurity, Institute of Microbiology and Epidemiology, Academy of Military Medical Sciences, Beijing, China
| | - Yijie Xu
- National Engineering Research Center for the Emergency Strategic Drug, Beijing Institute of Pharmacology and Toxicology, Beijing, China
- State Key Laboratory of Toxicology and Medical Countermeasures, Beijing Institute of Pharmacology and Toxicology, Beijing, China
| | - Xu Zhao
- Department of Hepatology, Fifth Medical Center of Chinese PLA General Hospital, Beijing, China
| | - Jing Zhang
- Qionglai Medical Center Hospital, Chengdu, China
| | - Ye Li
- The No 968 Hospital of PLA, Jinzhou, China
| | - Qingbin Meng
- State Key Laboratory of Toxicology and Medical Countermeasures, Beijing Institute of Pharmacology and Toxicology, Beijing, China
| | - Fang Yu
- School of Petrochemical Engineering, Liaoning Petrochemical University, Fushun, China
- National Engineering Research Center for the Emergency Strategic Drug, Beijing Institute of Pharmacology and Toxicology, Beijing, China
| | - Junhai Xiao
- National Engineering Research Center for the Emergency Strategic Drug, Beijing Institute of Pharmacology and Toxicology, Beijing, China
- State Key Laboratory of Toxicology and Medical Countermeasures, Beijing Institute of Pharmacology and Toxicology, Beijing, China
| | - Xingzhou Li
- National Engineering Research Center for the Emergency Strategic Drug, Beijing Institute of Pharmacology and Toxicology, Beijing, China
- State Key Laboratory of Toxicology and Medical Countermeasures, Beijing Institute of Pharmacology and Toxicology, Beijing, China
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Structural Insights into the Ligand–LsrK Kinase Binding Mode: A Step Forward in the Discovery of Novel Antimicrobial Agents. Molecules 2023; 28:molecules28062542. [PMID: 36985513 PMCID: PMC10056567 DOI: 10.3390/molecules28062542] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2023] [Revised: 03/03/2023] [Accepted: 03/06/2023] [Indexed: 03/14/2023] Open
Abstract
LsrK is a bacterial kinase that triggers the quorum sensing, and it represents a druggable target for the identification of new agents for fighting antimicrobial resistance. Herein, we exploited tryptophan fluorescence spectroscopy (TFS) as a suitable technique for the identification of potential LsrK ligands from an in-house library of chemicals comprising synthetic compounds as well as secondary metabolites. Three secondary metabolites (Hib-ester, Hib-carbaldehyde and (R)-ASME) showed effective binding to LsrK, with KD values in the sub-micromolar range. The conformational changes were confirmed via circular dichroism and molecular docking results further validated the findings and displayed the specific mode of interaction. The activity of the identified compounds on the biofilm formation by some Staphylococcus spp. was investigated. Hib-carbaldehyde and (R)-ASME were able to reduce the production of biofilm, with (R)-ASME resulting in the most effective compound with an EC50 of 14 mg/well. The successful application of TFS highlights its usefulness in searching for promising LsrK inhibitor candidates with inhibitor efficacy against biofilm formation.
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