A clash of quorum sensing vs quorum sensing inhibitors: an overview and risk of resistance

Discovery of 2,5-diketopiperazine alkaloids with quorum sensing inhibitory activity from the marine fungus Penicillium sp. ZJUT-34

One new 2,5-DKP derivative O-dihydroxycyclopenol (1) and seven known congeners 2-8 were isolated from the marine fungus Penicillium sp. ZJUT-34 cultured on rice medium. The planar structure of 1 was established by extensive spectroscopic analysis, including 1D, 2D NMR and HR-ESI-MS, while the relative configuration of 1 was determined by quantum chemical calculation. In the QS inhibitory assay, 1 significantly inhibited the production of violacein in Chromobacterium violaceum ATCC12472 (20.65%) at a concentration of 6.25 μg/mL without affecting the growth of the strain, as compared with norharmane (22.14%), a quorum sensing inhibitor (QSI) identified in our previous study. It represented the first report on the QS inhibitory activity of the seven-membered 2,5-DKPs. In addition, compounds 1-8 were subjected to antibacterial assay against six pathogenic bacteria Compound 8 exhibited comparable antibacterial activity against Enterococcus faecalis FA2-2 (MIC = 96 μg/mL) with the positive control gentamicin (MIC = 80 μg/mL).

Microbe-material hybrids for therapeutic applications

As natural living substances, microorganisms have emerged as useful resources in medicine for creating microbe-material hybrids ranging from nano to macro dimensions. The engineering of microbe-involved nanomedicine capitalizes on the distinctive physiological attributes of microbes, particularly their intrinsic "living" properties such as hypoxia tendency and oxygen production capabilities. Exploiting these remarkable characteristics in combination with other functional materials or molecules enables synergistic enhancements that hold tremendous promise for improved drug delivery, site-specific therapy, and enhanced monitoring of treatment outcomes, presenting substantial opportunities for amplifying the efficacy of disease treatments. This comprehensive review outlines the microorganisms and microbial derivatives used in biomedicine and their specific advantages for therapeutic application. In addition, we delineate the fundamental strategies and mechanisms employed for constructing microbe-material hybrids. The diverse biomedical applications of the constructed microbe-material hybrids, encompassing bioimaging, anti-tumor, anti-bacteria, anti-inflammation and other diseases therapy are exhaustively illustrated. We also discuss the current challenges and prospects associated with the clinical translation of microbe-material hybrid platforms. Therefore, the unique versatility and potential exhibited by microbe-material hybrids position them as promising candidates for the development of next-generation nanomedicine and biomaterials with unique theranostic properties and functionalities.

Vanadium-dependent haloperoxidases from diverse microbes halogenate exogenous alkyl quinolone quorum sensing signals

Site-selective vanadium-dependent haloperoxidases (VHPOs) are a unique enzyme family that catalyze selective halogenation reactions previously characterized within bacterial natural product biosynthetic pathways. However, the broader chemical roles and biological distribution of these halogenases remains to be explored. Using bioinformatic methods, we have defined a VHPO subfamily that regioselectively brominates alkyl quinolone (AQ) quorum sensing molecules. In vitro AQ halogenation activity was demonstrated from phylogenetically distinct bacteria lacking established AQ biosynthetic pathways and sourced from diverse environments. AQ-VHPOs show high sequence and biochemical similarities with negligible genomic synteny or biosynthetic gene cluster co-localization. Exposure of VHPO-containing microbes to synthetic AQs or established bacterial producers identifies the chemical and spatial response to subvert their bacteriostatic effects. The characterization of novel homologs from bacterial taxa without previously demonstrated vanadium enzymology suggests VHPO-mediated AQ bromination is a niche to manipulate the chemical ecology of microbial communities.

Dronedarone Enhances the Antibacterial Activity of Polymyxin B and Inhibits the Quorum Sensing System by Interacting with LuxS

Quorum sensing (QS) is considered an appealing target for interference with bacterial infections. β-Adrenergic blockers are promising anti-QS agents but do not have antibacterial activity. We assessed the potential ability of adrenergic receptor inhibitors to enhance the antibacterial activity of polymyxin B (PB) against Klebsiella pneumoniae and determined that dronedarone has the most potent activity both in vitro and in vivo. We found that dronedarone increases the thermal stability of LuxS, decreases the production of AI-2, and affects the biofilm formation of K. pneumoniae. We also identified the direct binding of dronedarone to LuxS. However, the mechanism by which dronedarone enhances the antibacterial activity of PB has not been elucidated and is worthy of further exploration. Our study provides a basis for the future development of drug combination regimens.

Nanomedicine against biofilm infections: A roadmap of challenges and limitations

Microbial biofilms are complex three-dimensional structures where sessile microbes are embedded in a polymeric extracellular matrix. Their resistance toward the host immune system as well as to a diverse range of antimicrobial treatments poses a serious health and development threat, being in the top 10 global public health threats declared by the World Health Organization. In an effort to combat biofilm-related microbial infections, several strategies have been developed to independently eliminate biofilms or to complement conventional antibiotic therapies. However, their limitations leave room for other treatment alternatives, where the application of nanotechnology to biofilm eradication has gained significant relevance in recent years. Their small size, penetration efficiency, and the design flexibility that they present makes them a promising alternative for biofilm infection treatment, although they also present set-backs. This review aims to describe the main possibilities and limitations of nanomedicine against biofilms, while covering the main aspects of biofilm formation and study, and the current therapies for biofilm treatment. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Infectious Disease Toxicology and Regulatory Issues in Nanomedicine > Toxicology of Nanomaterials Toxicology and Regulatory Issues in Nanomedicine > Regulatory and Policy Issues in Nanomedicine.

Synthesis, in Silico Study and Biological Evaluation of N-(Benzothiazol/Thiazol-2-yl)benzamide Derivatives as Quorum Sensing Inhibitors against Pseudomonas aeruginosa

The development of bacterial resistance to chemical therapy poses a severe danger to efficacy of treating bacterial infections. One of the key factors for resistance to antimicrobial medications is growth of bacteria in biofilm. Quorum sensing (QS) inhibition was created as an alternative treatment by developing novel anti-biofilm medicines. Cell-cell communication is impeded by QS inhibition, which targets QS signaling pathway. The goal of this work is to develop newer drugs that are effective against Pseudomonas aeruginosa by decreasing QS and acting as anti-biofilm agents. In this investigation, N-(benzo[d]thiazol-2-yl)benzamide/N-(thiazol-2-yl)benzamide derivatives 3a-h were designed and synthesized in good yields. Further, molecular docking analyses revealed that binding affinity values were founded -11.2 to -7.6 kcal/mol that were moderate to good. The physicochemical properties of these prepared compounds were investigated through in-silico method. Molecular dynamic simulation was also used to know better understanding of stability of the protein and ligand complex. Comparing N-(benzo[d]thiazol-2-yl)benzamide 3a to salicylic acid (4.40±0.10) that was utilised as standard for quorum sensing inhibitor, the anti-QS action was found greater for N-(benzo[d]thiazol-2-yl)benzamide 3a (4.67±0.45) than salicylic acid (4.40±0.10). Overall, research results suggested that N-(benzo[d]thiazol-2-yl)benzamide/N-(thiazol-2-yl)benzamide derivatives 3a-h may hold to develop new quorum sensing inhibitors.

Interkingdom Detection of Bacterial Quorum-Sensing Molecules by Mammalian Taste Receptors

Bitter and sweet taste G protein-coupled receptors (known as T2Rs and T1Rs, respectively) were originally identified in type II taste cells on the tongue, where they signal perception of bitter and sweet tastes, respectively. Over the past ~15 years, taste receptors have been identified in cells all over the body, demonstrating a more general chemosensory role beyond taste. Bitter and sweet taste receptors regulate gut epithelial function, pancreatic β cell secretion, thyroid hormone secretion, adipocyte function, and many other processes. Emerging data from a variety of tissues suggest that taste receptors are also used by mammalian cells to "eavesdrop" on bacterial communications. These receptors are activated by several quorum-sensing molecules, including acyl-homoserine lactones and quinolones from Gram-negative bacteria such as Pseudomonas aeruginosa, competence stimulating peptides from Streptococcus mutans, and D-amino acids from Staphylococcus aureus. Taste receptors are an arm of immune surveillance similar to Toll-like receptors and other pattern recognition receptors. Because they are activated by quorum-sensing molecules, taste receptors report information about microbial population density based on the chemical composition of the extracellular environment. This review summarizes current knowledge of bacterial activation of taste receptors and identifies important questions remaining in this field.