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Quorum sensing (QS) is a bacterial cell-to-cell communication mechanism that plays an essential role in bacterial pathogenesis. QS governs bacterial behavior and controls biofilm formation, which in turn contributes to antibiotic resistance. Therefore, identifying and synthesizing novel compounds to overcome QS and inhibit biofilm formation are essential. Coumarins are important plant-derived natural products with wide-ranging bioactivities and extensive applications, including antibacterial, antifungal, anticoagulant, antioxidant, anticancer, and anti-inflammatory properties. Additionally, coumarins are capable of QS rewiring and biofilm formation inhibition, leading to higher susceptibility to antimicrobial agents and less antibiotic resistance. Therefore, in this review, we aim to provide an overview of QS and biofilm formation. This review also discusses the role of natural and synthesized coumarins in controlling QS, inhibiting biofilm formation, and inducing synergy in antibiotic–coumarin combinations. Hence, this review emphasizes the potential of coumarin compounds to act as antibacterial agents and demonstrates their ability to alleviate antibiotic resistance. [ABSTRACT FROM AUTHOR]

Background: Biofilm formation in Helicobacter pylori (H. pylori) helps bacteria survive antibiotic exposure and supports bacterial colonization and persistence in the stomach. Most of the published articles have focused on one aspect of the biofilm. Therefore, we conducted the current study to better understand the mechanism of biofilm formation, how the biofilm contributes to antibiotic resistance, and how the biofilm modifies the medication delivery mechanism. Methods: We conducted a literature review analysis of the published articles on the Helicobacter pylori biofilm between 1998 and 2024 from the PubMed database to retrieve eligible articles. After applying the inclusion and exclusion criteria, two hundred and seventy-three articles were eligible for our study. Results: The results showed that biofilm formation starts as adhesion and progresses through micro-colonies, maturation, and dispersion in a planktonic form. Moreover, specific genes modulate each phase of biofilm formation. Few studies have shown that mechanisms, such as quorum sensing and diffusible signal factors, enhance coordination among bacteria when switching from biofilm to planktonic states. Different protein expressions were also observed between planktonic and biofilm strains, and the biofilm architecture was supported by exopolysaccharides, extracellular DNA, and outer membrane vesicles. Conclusions: This infrastructure is responsible for the increased survival of bacteria, especially in harsh environments or in the presence of antibiotics. Therefore, understanding the biofilm formation for H. pylori is crucial. This study illustrates biofilm formation in H. pylori to help improve the treatment of H. pylori infection. [ABSTRACT FROM AUTHOR]

The prevalence of multidrug resistance (MDR) and stagnant drug-development pipelines have led to the rapid rise of hard-to-treat antibiotic-resistant bacterial infections. These infectious diseases are no longer just nosocomial but are also becoming community-acquired. The spread of MDR has reached a crisis level that needs immediate attention. The landmark O'Neill report projects that by 2050, mortality rates associated with MDR bacterial infections will surpass mortality rates associated with individuals afflicted with cancer. Since conventional antimicrobials are no longer very reliable, it is of great importance to investigate different strategies to combat these life-threatening infectious diseases. Here, we provide an overview of recent advances in viable alternative treatment strategies mainly targeting a pathogen's virulence capability rather than viability. Topics include small molecule and immune inhibition of virulence factors, quorum sensing (QS) quenching, inhibition of biofilm development, bacteriophage-mediated therapy, and manipulation of an individual's macroflora to combat MDR bacterial infections. [ABSTRACT FROM AUTHOR]

Acinetobacter baumannii is an opportunistic Gram-negative pathogen with exquisite survival capabilities under various environmental conditions and displays widespread resistance to common antibiotics. A. baumannii is a leading cause of nosocomial infections that result in high morbidity and mortality rates. Accordingly, when multidrug resistance rates surpass threshold levels, the percentage of A. baumannii clinical isolates surges. Research into A. baumannii has increased in the past decade, and multiple mechanisms of pathogenesis have been identified, including mechanisms underlying biofilm development, quorum sensing, exotoxin production, secretion system utilization, and more. To date, the two gold-standard strains used to investigate different aspects of A. baumannii pathogenesis include ATCC 17978 and ATCC 19606. Here, we report a comparative characterization study of three additional A. baumannii clinical isolates obtained from different infection types and derived from different anatomical regions of infected patients. The comparison of three clinical isolates in addition to the ATCC strains revealed that the hypervirulent bacteremia clinical isolate, known as HUMC1, employs a completely different mechanism of pathogenesis when compared to all its counterparts. In stark contrast to the other genetic variants, the hypervirulent HUMC1 isolate does not form biofilms, is antibiotic-susceptible, and has the capacity to reach higher levels of quorum compared to the other clinically relevant strains. Our data also reveal that HUMC1 does not shed endotoxin into the extracellular milieu, rather secretes the evolutionarily conserved, host-mimicking, Zonula occludens toxin (Zot). Taken together, our hypothesis that HUMC1 cells have the ability to reach higher levels of quorum and lack biofilm production and endotoxin shedding, accompanied by the substantial elaboration of Zot, suggests a novel mechanism of pathogenesis that appears to afford the hypervirulent pathogen with stealth-like capabilities when disseminating through the circulatory system in a state of bacteremia. [ABSTRACT FROM AUTHOR]

Quorum sensing (QS) is a mechanism by which bacteria detect and respond to cell density, regulating collective behaviors. Burkholderia plantarii, the causal agent of rice seedling blight, employs the LuxIR-type QS system, common among Gram-negative bacteria, where LuxI-type synthase produces QS signals recognized by LuxR-type regulators to control gene expression. This study aimed to elucidate the QS mechanism in B. plantarii KACC18965. Through whole-genome analysis and autoinducer assays, the plaI gene, responsible for QS signal production, was identified. Motility assays confirmed that C8-homoserine lactone (C8-HSL) serves as the QS signal. Physiological experiments revealed that the QS-defective mutant exhibited reduced virulence, impaired swarming motility, and delayed biofilm formation compared to the wild type. Additionally, the QS mutant demonstrated weakened antibacterial activity against Escherichia coli and decreased phosphate solubilization. These findings indicate that QS in B. plantarii significantly influences various pathogenicity and survival traits, including motility, biofilm formation, antibacterial activity, and nutrient acquisition, highlighting the critical role of QS in pathogen virulence and adaptability. [ABSTRACT FROM AUTHOR]

Antibiotic resistance is a critical public health issue. Among the multi-drug resistant microorganisms in question, Pseudomonas aeruginosa has been designated by the WHO as a priority threat. Its virulence is orchestrated through quorum sensing (QS). This sophisticated communication network relies on the release and perception of autoinducers acting as population density indicators. Therefore, the interest of a quorum silencing pharmacological approach has unfolded to quench bacterial pathogenicity without impairing growth. In this article, we reported the development of a family of indazole–quinolone hybrids as anti-virulence agents. These new biaromatic compounds were designed as potential specific QS quenchers against P. aeruginosa. Our transdisciplinary research methodology included their synthesis using palladocatalyzed cross-coupling reactions, as well as their in silico physicochemical and in vitro biological evaluation. The hit 7-chloro-2-indazolyl-4-quinolone Ie shows a promising anti-biofilm and anti-pyocyanin efficiency (35% inhibition at 25 µM and 35% inhibition at 100 µM, respectively) without an anti-pseudomonal bacteriostatic effect. It also demonstrated a moderate eukaryotic cytotoxicity. Its anti-QS properties have been investigated using metabolomic and molecular modelling studies. [ABSTRACT FROM AUTHOR]

Biofilms are accumulations of microorganisms in an extracellular polymeric substance matrix which are composed of polysaccharides, proteins, lipids, and nucleic acids. Many bacteria can switch between a planktonic form and a biofilm form. The planktonic bacteria have relatively high cell growth and reproduction rates and have a reduced likelihood of survival but can adapt to occupy new habitats. The biofilm state appears to be a natural and predominant state of bacteria. The need for the formation of bacterial biofilm is that it enhances the tolerance of bacteria to harsh environmental conditions, thereby allowing bacteria to avoid being washed away by water flow or the bloodstream by simply attaching to a surface or tissue, and the EPS matrix protects bacteria cells, in deeper layers, against antimicrobial agents, probably by limiting the diffusion of these agents. Biofilm formation steps are initial contact/attachment to the surface, followed by micro-colony formation, maturation and formation of the architecture of the biofilm, and finally detachment/dispersion of the biofilm. Once formed, biofilm restricts bacterial mobility and increases cell density. Secretions of autoinducers into the environment are critical for cross-signaling between bacteria. This cross-talk is called quorum sensing (QS). Quorum sensing is a cell–cell communication mechanism between bacteria that allows specific processes to be controlled, such as biofilm formation and virulence factor expression. Bacterial quorum sensing signaling mainly consists of acyl-homoserine lactones (produced by Gram-negatives), autoinducing peptides (produced by Gram-positives), and autoinducer-2 (produced by both Gram-negatives and Gram-positives). Therefore, this review is aimed at how bacterial biofilms work and are formed. [ABSTRACT FROM AUTHOR]

The escalating risks of drought and salinization due to climate change and anthropogenic activities are a major global concern. Rhizobium–legume (herb or tree) symbiosis is proposed as an ideal solution for improving soil fertility and rehabilitating arid lands, representing a crucial direction for future research. Consequently, several studies have focused on enhancing legume tolerance to drought and salinity stresses using various techniques, including molecular-based approaches. These methods, however, are costly, time-consuming, and cause some environmental issues. The multiplicity of beneficial effects of soil microorganisms, particularly plant growth-promoting bacteria (PGPB) or plant-associated microbiomes, can play a crucial role in enhancing legume performance and productivity under harsh environmental conditions in arid zones. PGPB can act directly or indirectly through advanced mechanisms to increase plant water uptake, reduce ion toxicity, and induce plant resilience to osmotic and oxidative stress. For example, rhizobia in symbiosis with legumes can enhance legume growth not only by fixing nitrogen but also by solubilizing phosphates and producing phytohormones, among other mechanisms. This underscores the need to further strengthen research and its application in modern agriculture. In this review, we provide a comprehensive description of the challenges faced by nitrogen-fixing leguminous plants in arid and semi-arid environments, particularly drought and salinity. We highlight the potential benefits of legume–rhizobium symbiosis combined with other PGPB to establish more sustainable agricultural practices in these regions using legume–rhizobium–PGPB partnerships. [ABSTRACT FROM AUTHOR]

The increase in antibiotic-resistant bacteria presents a significant risk to worldwide public health, emphasizing the necessity of novel approaches to address infections. Quorum sensing, an essential method of communication among bacteria, controls activities like the formation of biofilms, the production of virulence factors, and the synthesis of secondary metabolites according to the number of individuals in the population. Quorum quenching, which interferes with these processes, emerges as a vital approach to diminish bacterial virulence and prevent biofilm formation. Nanocarriers, characterized by their small size, high surface-area-to-volume ratio, and modifiable surface chemistry, offer a versatile platform for the disruption of bacterial communication by targeting various stages within the quorum sensing pathway. These features allow nanocarriers to infiltrate biofilms, disrupt cell membranes, and inhibit bacterial proliferation, presenting a promising alternative to traditional antibiotics. Integrating nanocarrier-based systems into combination therapies provides a multi-pronged approach to infection control, enhancing both the efficacy and specificity of treatment regimens. Nonetheless, challenges related to the stability, safety, and clinical effectiveness of nanomaterial-based antimicrobial treatments remain. Continued research and development are essential to overcoming these obstacles and fully harnessing the potential of nano-antimicrobial therapies. This review emphasizes the importance of quorum sensing in bacterial behavior and highlights the transformative potential of nanotechnology in advancing antimicrobial treatments, offering innovative solutions to combat antibiotic-resistant pathogens. [ABSTRACT FROM AUTHOR]

Background/Objectives: Bacterial resistance and virulence are challenges in treating bacterial infections, especially in Klebsiella pneumoniae. Plants of the Launaea Cass. genus are used traditionally to address a variety of diseases, including infections, but the potential bioactive compounds are unknown. Our goals were to verify the potential contribution of two major polyacetylene glycosides isolated from our previous study, (3S,6E,12E)-6,12-tetradecadiene-8,10-diyne-1-ol 3-O-β-D-glucopyranoside (1) and bidensyneoside A (syn. gymnasterkoreaside A) [(3R,8E)-3-hydroxy-8-decene-4,6-diyn-1-yl β-D-glucopyranoside] (2), to the anti-infective properties of Launaea capitata and to develop a dependable HPLC method for their quantification; Methods: On a panel of K. pneumoniae clinical isolates, the antibacterial action of 1, 2, and the methanol extract of the whole L. capitata plant were evaluated by broth microdilution assay, while their antibiofilm action was evaluated by the crystal violet assay. qRT-PCR investigated luxS, mrkA, wzm, and wbbm genes that encode biofilm formation and quorum sensing (QS). The antibacterial activity of 1 was revealed by employing mice infection. Chromatographic separation was conducted using isocratic elution on a Hypersil BDS C18 column using a photodiode array (PDA) detector; Results: Compound 1 showed antibacterial activity with MIC values of 16–128 µg/mL. It remarkably reduced strong and moderate biofilm-forming bacterial isolates from 84.21% to 42.1% compared with the extract (68.42%) and 2 (78.95%). Compound 1 also downregulated the QS genes, luxS, mrkA, wzm, and wbbm, and exhibited in vivo antibacterial action through the enhancement of the histological construction of the liver and spleen, decreased TNF-α immunoreaction, bacterial burden, and the inflammatory mediators IL-1β and IL-6. A successful HPLC-PDA approach was developed to separate the binary mixture of 1 and 2 in less than 10 min with high sensitivity, with detection limits down to 0.518 and 0.095 µg/mL for 1 and 2, respectively; Conclusions: Compound 1 exhibited remarkable antibacterial and antibiofilm properties and may contribute to the anti-infectious traditional uses of L. capitata, meriting further clinical studies and serving as a reliable quality control biomarker for the plant. [ABSTRACT FROM AUTHOR]

Recently, studies suggest that the protective effects of Lactobacillus within the female reproductive tract may be partly due to their ability to form biofilms. This study aims to explore the possibility that Lactobacillus can produce key mediators to further bolster the survival of biofilms in human vaginal microbiomes. Three bacterial species, namely, Lactobacillus gasseri, L. crispatus, and L. jensenii, sourced from human female subjects were used to carry out experiments examining the growth of biofilms using a microfermenter system. The bacteria were used to inoculate a glass rod spatula which was subsequently transferred to the microfermenter system. The resulting biofilm growing on the glass spatula was harvested in media and stored in a −80 °C freezer for gas chromatography–mass spectroscopy analysis. We found that quorum sensing compounds, acyl homoserine lactones (AHLs), were detected in the biofilm of L. crispatus and L. jensenii, but none were detected in L. gasseri. The biofilm produced by L. crispatus and L. jensenii was much higher in quantity than the biofilm produced by L. gasseri. Aside from oligopeptides quorum sensing, lactobacilli were found to also have AHL compounds that may help them produce more biofilms and improve the survival and growth of their bacterial communities in the female genital area. [ABSTRACT FROM AUTHOR]

Staphylococcus aureus acts both as a colonizing commensal bacterium and invasive pathogen. Nasal colonization is associated with an increased risk of infection caused by the identical strain. In patients with atopic dermatitis (AD), the degree of S. aureus colonization is associated with the severity of the disease. Here, we comparatively analyzed the in vivo transcriptional profile of S. aureus colonizing the nose and non-diseased skin (non-lesional skin) as opposed to the diseased skin (lesional skin—defined here as infection) of 12 patients with AD. The transcriptional profile during the asymptomatic colonization of the nose closely resembled that of the lesional skin samples for many of the genes studied, with an elevated expression of the genes encoding adhesion-related proteins and proteases. In addition, the genes that modify and remodel the cell wall and encode proteins that facilitate immune evasion showed increased transcriptional activity. Notably, in a subgroup of patients, the global virulence regulator Agr (accessory gene regulator) and downstream target genes were inactive during nasal colonization but upregulated in the lesional and non-lesional skin samples. Taken together, our results demonstrate a colonization-like transcriptional profile on diseased skin and suggest a role for the peptide quorum sensing system Agr during the transition from asymptomatic nasal colonization to skin colonization/infection. [ABSTRACT FROM AUTHOR]

The production of public goods is a necessary condition for the survival of the species, but it comes at the expense of individual growth. In a prototype bacterial colony, we model the role of quorum sensing as a resource redistribution mechanism. Two types of bacterial colonies are analyzed, one made up of a single strain and one made up of two different strains. Based on a recent series of experimental data present in the literature, we analyze two types of strains with different extinction times: strains that consume available resources very quickly, therefore becoming extinct quickly, and strains that consume resources slowly and die due to aging. We show that the proposed quorum sensing model describes the main experimental result that coexistence may favor the survival of both strains. Furthermore, the production of public goods is maximized when both types of individuals have the maximum proliferation output. Finally, we highlight the role played by so-called dormant cells in the duration of survival time. These cells are of particular interest because their ability to counteract different types of stress (e.g., the use of antibiotics) still constitutes a challenge. [ABSTRACT FROM AUTHOR]

Bacterial adhesion and biofilm maturation is significantly influenced by surface properties, encompassing both bare surfaces and single or multi-layered coatings. Hence, there is an utmost interest in exploring the intricacies of gene regulation in sulfate-reducing bacteria (SRB) on copper and graphene-coated copper surfaces. In this study, Oleidesulfovibrio alaskensis G20 was used as the model SRB to elucidate the pathways that govern pivotal roles during biofilm formation on the graphene layers. Employing a potent reporter green fluorescent protein (GFP) tagged to O. alaskensis G20, the spatial structure of O. alaskensis G20 biofilm on copper foil (CuF), single-layer graphene-coated copper (Cu-GrI), and double-layer graphene-coated copper (Cu-GrII) surfaces was investigated. Biofilm formation on CuF, Cu-GrI, and Cu-GrII surfaces was quantified using CLSM z-stack images within COMSTAT v2 software. The results revealed that CuF, Cu-GrI, and Cu-GrII did not affect the formation of the GFP-tagged O. alaskensis G20 biofilm architecture. qPCR expression showed insignificant fold changes for outer membrane components regulating the quorum-sensing system, and global regulatory proteins between the uncoated and coated surfaces. Notably, a significant expression was observed within the sulfate reduction pathway confined to dissimilatory sulfite reductases on the Cu-GrII surface compared to the CuF and Cu-GrI surfaces. [ABSTRACT FROM AUTHOR]

Pseudomonas aeruginosa is an opportunistic pathogen that requires iron to survive in the host; however, the host immune system limits the availability of iron. Pyochelin (PCH) is a major siderophore produced by P. aeruginosa during infection, which can help P. aeruginosa survive in an iron-restricted environment and cause infection. The infection activity of P. aeruginosa is regulated by the Pseudomonas quinolone signal (PQS) quorum-sensing system. The system uses 2-heptyl-3-hydroxy-4-quinolone (PQS) or its precursor, 2-heptyl-4-quinolone (HHQ), as the signal molecule. PQS can control specific life processes such as mediating quorum sensing, cytotoxicity, and iron acquisition. This review summarizes the biosynthesis of PCH and PQS, the shared transport system of PCH and PQS, and the regulatory relationship between PCH and PQS. The correlation between the PQS and PCH is emphasized to provide a new direction for future research. [ABSTRACT FROM AUTHOR]

Lactic acid bacteria (LAB) are the most common probiotics, and they present excellent inhibitory effects on pathogenic bacteria. This study aimed to explore the anti-biofilm potential of the purified active substance of Lactiplantibacillus plantarum, named Z102-E. The effects of Z102-E on Listeria monocytogenes were investigated in detail, and a transcriptomic analysis was conducted to reveal the anti-biofilm mechanism. The results indicated that the sub-MIC of Z102-E (3.2, 1.6, and 0.8 mg/mL) decreased the bacterial growth and effectively reduced the self-aggregation, surface hydrophobicity, sugar utilization, motility, biofilm formation, AI-2 signal molecule, contents of extracellular polysaccharides, and extracellular protein of L. monocytogenes. Moreover, the inverted fluorescence microscopy observation confirmed the anti-biofilm effect of Z102-E. The transcriptomic analysis indicated that 117 genes were up-regulated and 214 were down-regulated. Z102-E regulated the expressions of genes related to L. monocytogenes quorum sensing, biofilm formation, etc. These findings suggested that Z102-E has great application potential as a natural bacteriostatic agent. [ABSTRACT FROM AUTHOR]

This study reports for the first time the isolation of four diterpenoid compounds: 15-Hydroxy-12-oxo-abietic acid (1), 12α-hydroxyabietic acid (2), (−)-Jolkinolide E (3), and 15-Hydroxydehydroabietic acid (4) from Clinopodium bolivianum (C. bolivianum). The findings demonstrate that both the dichloromethane/methanol (DCMECB) extract of C. bolivianum and the isolated compounds exhibit significant anti-inflammatory (inhibition of NF-κB activation), antibacterial (primarily against Gram-positive bacteria), and anti-biofilm (primarily against Gram-negative bacteria) activities. Among the isolated diterpenes, compounds 3 and 4 showed notable anti-inflammatory effects, with IC50 values of 17.98 μM and 23.96 μM for compound 3, and 10.79 μM and 17.37 μM for compound 4, in the HBEC3-KT and MRC-5 cell lines. Regarding their antibacterial activity, compounds 3 and 4 were particularly effective, with MIC values of 0.53–1.09 μM and 2.06–4.06 μM, respectively, against the S. pneumoniae and S. aureus Gram-positive bacteria. Additionally, these compounds demonstrated significant anti-biofilm and anti-quorum sensing activities, especially against Gram-negative bacteria (H. influenzae and L. pneumophila). We also explain how compound 3 (BIC = 1.50–2.07 μM, Anti-QS = 0.31–0.64 μM) interferes with quorum sensing due to its structural homology with AHLs, while compound 4 (BIC = 4.65–7.15 μM, Anti-QS = 1.21–2.39 μM) destabilises bacterial membranes due to the presence and position of its hydroxyl groups. These results support the traditional use of C. bolivianum against respiratory infections caused by both Gram-positive and Gram-negative bacteria. Furthermore, given the increasing antibiotic resistance and biofilm formation by these bacteria, there is a pressing need for the development of new, more active compounds. In this context, compounds 3 and 4 isolated from C. bolivianum offer promising potential for the development of a library of new, more potent, and selective drugs. [ABSTRACT FROM AUTHOR]

Cyclodextrins, commonly used as excipients in antifungal formulations to improve the physicochemical properties and availability of the host molecules, have not been systematically studied for their effects and bioactivity without a complex active substance. This paper evaluates the effects of various cyclodextrins on the physiology of the test organism Candida boidinii. The research examines their impact on yeast growth, viability, biofilm formation and morphological changes. Native ACD, BCD, randomly methylated α- and β-CD and quaternary ammonium α-CD and β-CD were investigated in the 0.5–12.5 mM concentration range in both static and dynamic systems. The study revealed that certain cyclodextrins exhibited notable antifungal effects (up to ~69%) in dynamic systems; however, the biofilm formation was enhanced in static systems. The magnitude of these effects was influenced by several variables, including the size of the internal cavity, the concentration and structure of the cyclodextrins, and the contact time. Furthermore, the study found that CDs exhibited distinct effects in both static and dynamic systems, potentially related to their tendency to form aggregates. The findings suggest that cyclodextrins may have the potential to act as antifungal agents or growth promoters, depending on their structure and surrounding environments. [ABSTRACT FROM AUTHOR]

Antibiotic resistance is a major problem and a major global health concern. In total, there are 16 million deaths yearly from infectious diseases, and at least 65% of infectious diseases are caused by microbial communities that proliferate through the formation of biofilms. Antibiotic overuse has resulted in the evolution of multidrug-resistant (MDR) microbial strains. As a result, there is now much more interest in non-antibiotic therapies for bacterial infections. Among these revolutionary, non-traditional medications is quorum sensing inhibitors (QSIs). Bacterial cell-to-cell communication is known as quorum sensing (QS), and it is mediated by tiny diffusible signaling molecules known as autoinducers (AIs). QS is dependent on the density of the bacterial population. QS is used by Gram-negative and Gram-positive bacteria to control a wide range of processes; in both scenarios, QS entails the synthesis, identification, and reaction to signaling chemicals, also known as auto-inducers. Since the usual processes regulated by QS are the expression of virulence factors and the creation of biofilms, QS is being investigated as an alternative solution to antibiotic resistance. Consequently, the use of QS-inhibiting agents, such as QSIs and quorum quenching (QQ) enzymes, to interfere with QS seems like a good strategy to prevent bacterial infections. This review sheds light on QS inhibition strategy and mechanisms and discusses how using this approach can aid in winning the battle against resistant bacteria. [ABSTRACT FROM AUTHOR]

Simple Summary: Avian pathogenic Escherichia coli (APEC) constitutes a notable etiological agent of colibacillosis, an inflammatory disease in birds that leads to considerable economic losses within the poultry industry. In this study, we probed into the impact of the quorum sensing regulator SdiA on the transcriptional profiling of an APEC strain and proved the potential regulatory role of SdiA in biofilm formation, motility, and drug resistance. The discoveries disclose the involvement of SdiA in the pathogenesis of APEC and will furnish some novel insights into the prevention and control of colibacillosis induced by APEC. Avian pathogenic Escherichia coli (APEC) constitutes a significant cause of colibacillosis, a localized or systemic inflammatory disorder in avian species, resulting in considerable economic losses within the global poultry industry. SdiA (suppressor of division inhibitor) is a transcription factor recognized as a LuxR homolog in Escherichia coli, regulating various behaviors, including biofilm formation, multidrug resistance, and the secretion of virulence factors. However, the function of SdiA in APEC strains and its correlation with virulence and multidrug resistance remains unknown. This study probed into the function of SdiA by analyzing the effect of sdiA deletion on the transcription profile of an APEC strain. The microarray data revealed that SdiA upregulates 160 genes and downregulates 59 genes, exerting a particularly remarkable influence on the transcription of multiple virulence genes. A series of antibiotic sensitivity tests, biofilm formation assays, motility assays, and transcriptome analyses were performed, while a Normality test and t-test were conducted on the datasets. This research confirmed that SdiA inhibits biofilm formation by 1.9-fold (p-value < 0.01) and motility by 1.5-fold (p-value < 0.01). RT-qPCR revealed that SdiA positively regulates multidrug resistance by upregulating the expression of yafP, cbrA, and eamB. Collectively, the results of this study indicate the role of SdiA in the pathogenesis of APEC by controlling biofilm formation, motility, and multidrug resistance. [ABSTRACT FROM AUTHOR]

Bacillus licheniformis is recognised as an exceptional expression platform in biomanufacturing due to its ability to produce high-value products. Consequently, metabolic engineering of B. licheniformis is increasingly pursued to enhance its utility as a biomanufacturing vehicle. Effective B. licheniformis cell factories require promoters that enable regulated expression of target genes. This review discusses recent advancements in the characterisation, synthesis, and engineering of B. licheniformis promoters. We highlight the application of constitutive promoters, quorum sensing promoters, and inducible promoters in protein and chemical synthesis. Additionally, we summarise efforts to expand the promoter toolbox through hybrid promoter engineering, transcription factor-based inducible promoter engineering, and ribosome binding site (RBS) engineering. [ABSTRACT FROM AUTHOR]

Biofilms, aggregates of bacteria enclosed in a self-produced matrix, have been implicated in various pediatric respiratory infections, including acute otitis media (AOM), otitis media with effusion (OME), adenoiditis, protracted bacterial bronchitis, and pulmonary exacerbations in cystic fibrosis. These infections are prevalent in children and often associated with biofilm-producing pathogens, leading to recurrent and chronic conditions. Biofilms reduce antibiotic efficacy, contributing to treatment failure and disease persistence. This narrative review discusses biofilm production by respiratory pathogens such as Streptococcus pneumoniae, non-typeable Haemophilus influenzae, Pseudomonas aeruginosa, and Staphylococcus aureus. It examines their mechanisms of biofilm formation, antibiotic resistance, and the challenges they present in clinical treatment. Various antibiofilm strategies have shown promise in vitro and in animal studies, including the use of N-acetylcysteine, enzymes like dispersin B, and agents disrupting quorum sensing and biofilm matrix components. However, their clinical application, particularly in children, remains limited. Traditional treatments for biofilm-associated diseases have not significantly evolved, even with biofilm detection. The transition from experimental findings to clinical practice is complex and requires robust clinical trials and standardized biofilm detection protocols. Addressing biofilms in pediatric respiratory infections is crucial for improving treatment outcomes and managing recurrent and chronic diseases effectively. [ABSTRACT FROM AUTHOR]

Hospital-acquired antibiotic-resistant pneumonia is one of the major causes of mortality around the world that pose a catastrophic threat. Pseudomonas aeruginosa is one of the most significant opportunistic pathogens responsible for hospital-acquired pneumonia and gained resistance to the majority of conventional antibiotics. There is an urgent need for antibiotic alternatives to control drug-resistant pneumonia and other related respiratory infections. In the present study, we explored the antibacterial potential of cineole in combination with homeopathic medicines against biofilm-forming drug-resistant P. aeruginosa. Out of 26 selected and screened homeopathic medicines, Hypericum Perforatum (HyPer) was found to eradicate biofilm-forming drug-resistant P. aeruginosa most effectively when used in combination with cineole. Interestingly, the synergistic action of HyPer and cineole was also found to be similarly effective against planktonic cells of P. aeruginosa. Further, the potential synergistic killing mechanisms of cineole and HyPer were determined by analyzing zeta membrane potential, outer membrane permeability, and DNA release from P. aeruginosa cells upon treatment with cineole and HyPer. Additionally, molecular docking analysis revealed strong binding affinities of hypericin (an active ingredient of HyPer) with the PqsA (a quorum sensing protein) of P. aeruginosa. Overall, our findings revealed the potential synergistic action of cineole and HyPer against biofilm-forming drug-resistant P. aeruginosa. Cineole and HyPer could be used in combination with other bronchodilators as inhalers to control the biofilm-forming drug-resistant P. aeruginosa. [ABSTRACT FROM AUTHOR]

Pseudomonas aeruginosa is an opportunistic Gram-negative bacterium that remains a prevalent clinical and environmental challenge. Quorum-sensing (QS) molecules are effective biomarkers in pinpointing the presence of P. aeruginosa. This study aimed to develop a convenient-to-use, whole-cell biosensor using P. aeruginosa reporters individually encapsulated within alginate-poly-L-lysine (alginate-PLL) microbeads to specifically detect the presence of bacterial autoinducers. The PLL-reinforced microbeads were prepared using a two-step method involving ionic cross-linking and subsequent coating with thin layers of PLL. The alginate-PLL beads showed good stability in the presence of a known cation scavenger (sodium citrate), which typically limits the widespread applications of calcium alginate. In media containing synthetic autoinducers—such as N-(3-oxo dodecanoyl) homoserine lactone (3-oxo-C12-HSL) and N-butanoyl-L-homoserine lactone (C4-HSL), or the cell-free supernatants of planktonic or the flow-cell biofilm effluent of wild P. aeruginosa (PAO1)—the encapsulated bacteria enabled a dose-dependent detection of the presence of these QS molecules. The prepared bioreporter beads remained stable during prolonged storage at 4 and −80 °C and were ready for on-the-spot sensing without the need for recovery. The proof-of-concept, optical fiber-based, and whole-cell biosensor developed here demonstrates the practicality of the encapsulated bioreporter for bacterial detection based on specific QS molecules. [ABSTRACT FROM AUTHOR]

RhlR plays a key role in the quorum sensing of Pseudomonas aeruginosa. The current structure–activity relationship (SAR) studies of RhlR inhibitors mainly focus on elucidating the functional groups. Based on a systematic review of previous research on RhlR inhibitors, this study aims to establish a systematic, hierarchical screening model for RhlR inhibitors. We initially established a database and utilized principal component analysis (PCA) to categorize the inhibitors into two classes. Based on the training set, pharmacophore models were established to elucidate the structural characteristics of ligands. Subsequently, molecular docking, molecular dynamics simulations, and the calculation of binding free energy and strain energy were performed to validate the crucial interactions between ligands and receptors. Then, the screening criteria for RhlR inhibitors were established hierarchically based on ligand structure characteristics, ligand–receptor interaction, and receptor affinity. Test sets were finally employed to validate the hierarchical virtual screening model by comparing it with the current SAR studies of RhlR inhibitors. The hierarchical screening model was confirmed to possess higher accuracy and a true positive rate, which holds promise for subsequent screening and the discovery of active RhlR inhibitors. [ABSTRACT FROM AUTHOR]

LuxR-type regulators play pivotal roles in regulating numerous bacterial processes, including bacterial motility and virulence, thereby exerting a significant influence on bacterial behavior and pathogenicity. Xanthomonas oryzae pv. oryzicola, a rice pathogen, causes bacterial leaf streak. Our research has identified VmsR, which is a response regulator of the two-component system (TCS) that belongs to the LuxR family. These findings of the experiment reveal that VmsR plays a crucial role in regulating pathogenicity, motility, biofilm formation, and the production of extracellular polysaccharides (EPSs) in Xoc GX01. Notably, our study shows that the vmsR mutant exhibits a reduced swimming motility but an enhanced swarming motility. Furthermore, this mutant displays decreased virulence while significantly increasing EPS production and biofilm formation. We have uncovered that VmsR directly interacts with the promoter regions of fliC and fliS, promoting their expression. In contrast, VmsR specifically binds to the promoter of gumB, resulting in its downregulation. These findings indicate that the knockout of vmsR has profound effects on virulence, motility, biofilm formation, and EPS production in Xoc GX01, providing insights into the intricate regulatory network of Xoc. [ABSTRACT FROM AUTHOR]

Biofilms play a decisive role in the infectious process and the development of antibiotic resistance. The establishment of bacterial biofilms is regulated by a signal-mediated cell–cell communication process called "quorum sensing" (QS). The identification of quorum sensing inhibitors (QSI) to mitigate the QS process may facilitate the development of novel treatment strategies for biofilm-based infections. In this study, the traditional medicinal plant Ocimum sanctum was screened for QS inhibitory potential. Sub-MICs of the extract significantly affected the secretion of EPS in Gram-negative human pathogens such as Escherichia coli, Pseudomonas aeruginosa PAO1, Proteus mirabilis, and Serratia marcescens, as well as aquaculture pathogens Vibrio harveyi, V. parahaemolyticus, and V. vulnificus, which render the bacteria more sensitive, leading to a loss of bacterial biomass from the substratum. The observed inhibitory activity of the O. sanctum extract might be attributed to the presence of eugenol, as evidenced through ultraviolet (UV)-visible, gas chromatography-mass spectroscopy (GC–MS), Fourier transformer infrared (FTIR) spectroscopy analyses, and computational studies. Additionally, the QSI potential of eugenol was corroborated through in vitro studies using the marker strain Chromobacterium violaceum. [ABSTRACT FROM AUTHOR]

The capsule-associated protein 10 gene (CAP10) is indispensable due to its involvement in pod formation and virulence maintenance in Cryptococcus neoformans. The function of the CAP10 gene in nematode-predatory fungi remains unreported. As a typical nematode-trapping fungus, Dactylellina haptotyla efficiently captures nematodes using adhesive knobs, which has potential applications in the biological control of plant-parasitic nematodes. In this study, we investigated the function of DHXT1 (a CAP10 homologous protein) in D. haptotyla–nematode interactions based on the disruption and overexpression of DHXT1, phenotypic analysis and metabolomic analysis. As a result, it was shown that the disruption of the DHXT1 gene causes a marked decrease in the number of adhesive knobs, and on the contrary, the overexpression of the DHXT1 gene causes a substantial increase in the number of adhesive knobs. Interestingly, the variety of metabolites increased with the disruption of the DHXT1 and decreased with the overexpression of the DHXT1 gene. The results suggest that DHXT1 effects pathogenicity through its involvement in adhesive knobs' formation and metabolite synthesis and serves as a key virulence factor in D. haptotyla. [ABSTRACT FROM AUTHOR]

Dasania marina (isolate SD1D, with 98.5% sequence similarity to Dasania marina DMS 21967 KOPRI 20902) is a marine bacterium that was isolated from ballast tank fluids as part of a biofilm study in 2014. Our previous work indicated that although this strain produced no detectable biofilm, it was the only isolate to produce N-acyl homoserine lactones (AHLs) in assays using the broad-range reporter strain, Agrobacterium tumefaciens KYC55. The goal of the current study was to determine the types of AHL molecules produced by the D. marina isolate using gas chromatography–mass spectroscopy (GCMS) and C4- to C14-AHL as standards. A time course assay indicated that the D. marina strain produced the highest level of AHLs at 20 h of growth. When extracts were subjected to GCMS, detectable levels of C8- and C10-AHL and higher levels of C12-AHL were observed. Interestingly, several biofilm-forming isolates obtained from the same source also produced detectable amounts of several AHLs. Of the isolates tested, a strain designated SD5, with 99.83% sequence similarity to Alteromonas tagae BCRC 17571, produced unstable biofilms, yet detectable levels of C6-, C8-, C10- and C12-AHL, and isolate SD8, an Alteromonas oceani S35 strain (98.85% sequence similarity), produced robust and stable biofilms accompanied by detectable levels of C8- and C12-AHL. All isolates tested produced C12-AHL at higher levels than the other AHLs. Results from this study suggest that quorum sensing and biofilm formation are uncoupled in D. marina. Whether the suite of AHLs produced by this isolate could modulate biofilm formation in other strains requires further study. [ABSTRACT FROM AUTHOR]

Microcystis-dominated cyanobacterial blooms (MCBs) frequently occur in freshwaters worldwide due to massive Microcystis colony formation and severely threaten human and ecosystem health. Quorum sensing (QS) is a direct cause of Microcystis colony formation that drives MCBs outbreak by regulating Microcystis population characteristics and behaviors. Many novel findings regarding the fundamental knowledge of the Microcystis QS phenomenon and the signaling molecules have been documented. However, little effort has been devoted to comprehensively summarizing and discussing the research progress and exploration directions of QS signaling molecules-mediated QS system in Microcystis. This review summarizes the action process of N-acyl homoserine lactones (AHLs) as major signaling molecules in Microcystis and discusses the detailed roles of AHL-mediated QS system in cellular morphology, physiological adaptability, and cell aggregation for colony formation to strengthen ecological adaptability and competitive advantage of Microcystis. The research progress on QS mechanisms in Microcystis are also summarized. Compared to other QS systems, the LuxI/LuxR-type QS system is more likely to be found in Microcystis. Also, we introduce quorum quenching (QQ), a QS-blocking process in Microcystis, to emphasize its potential as QS inhibitors in MCBs control. Finally, in response to the research deficiencies and gaps in Microcystis QS, we propose several future research directions in this field. This review deepens the understanding on Microcystis QS knowledge and provide theoretical guidance in developing strategies to monitor, control, and harness MCBs. [ABSTRACT FROM AUTHOR]

Simple Summary: Listeria pathogenicity island 4 (LIPI-4)—which is composed of six genes, including EⅡB—has been identified as a specific virulence factor closely related to infections of the nervous system and the placenta. This study examined the virulence effect of LIPI-4 EⅡB. Deletion of EⅡB reduced the biofilm formation ability and cell intracellular proliferation capacity of Listeria monocytogenes, as well as bacterial load in mice. In addition, EⅡB was found to regulate the transcription levels of genes related to virulence and biofilm formation. These findings provide a foundation for further examinations of the pathogenic mechanisms of LIPI-4 and EⅡB in L. monocytogenes. To explore the role of the membrane permease ⅡB (EⅡB) gene of Listeria pathogenicity island 4 (LIPI-4) in the virulence of Listeria monocytogenes, both an EⅡB deletion strain (∆EⅡB) and a complemented strain were constructed. In vitro experiments demonstrated that EⅡB deletion affected the biofilm formation ability of the wild-type strain (Lm928). Moreover, this deletion decreased the intracellular proliferation abilities of L. monocytogenes. Mice infected with ∆EⅡB survived longer and experienced less weight loss on days 1, 2, and 3 post-infection. The bacterial load in the liver tissue of ∆EⅡB-infected mice was significantly reduced, and a considerable decrease in the blood levels of inflammatory cytokines IL-β, IL-6, IL-10, and TNF-α were observed. Following EⅡB deletion, 65% (13/20) of genes were downregulated, 25% (5/20) were upregulated, and 10% (2/20) showed no change. These findings suggest that EⅡB deletion may reduce both the in vivo and in vitro virulence levels as well as the biofilm formation ability of Lm928 by downregulating the transcription levels of genes associated with virulence and biofilm formation. These findings provide a foundation for further examining the pathogenic mechanisms of LIPI-4 and EⅡB in L. monocytogenes. [ABSTRACT FROM AUTHOR]

Porphyromonas gingivalis is crucial for the pathogenesis of periodontitis. This research investigated the effects of the fruit-derived flavonoid phloretin and its analogs on the growth of pure P. gingivalis and the flora of P. gingivalis mixed with the symbiotic oral pathogens Fusobacterium nucleatum and Streptococcus mitis. The results showed that the tested flavonoids had little effect on the biofilm amount of pure P. gingivalis, but significantly reduced the biofilm amount of mixed flora to 83.6~89.1%. Biofilm viability decreased to 86.7~92.8% in both the pure- and mixed-bacterial groups after naringenin and phloretin treatments. SEM showed that phloretin and phlorizin displayed a similar and remarkable destructive effect on P. gingivalis and the mixed biofilms. Transcriptome analysis confirmed that biofilm formation was inhibited by these flavonoids, and phloretin significantly regulated the transcription of quorum sensing. Phlorizin and phloretin reduced AI-2 activity to 45.9% and 55.4%, respectively, independent of the regulation of related gene transcription. This research marks the first finding that these flavonoids possess anti-biofilm properties against P. gingivalis and its intricate bacterial community, and the observed performance variations, driven by structural differences, underscore the existence of intriguing structure–activity relationships. [ABSTRACT FROM AUTHOR]

With the widespread phenomenon of antibiotic resistance and the diffusion of multiple drug-resistant bacterial strains, enormous efforts are being conducted to identify suitable alternative agents against pathogenic microorganisms. Since an association between biofilm formation and antibiotic resistance phenotype has been observed, a promising strategy pursued in recent years focuses on controlling and preventing this formation by targeting and inhibiting the Quorum Sensing (QS) system, whose central role in biofilm has been extensively demonstrated. Therefore, the research and development of Quorum Quenching (QQ) compounds, which inhibit QS, has gradually attracted the attention of researchers and has become a new strategy for controlling harmful microorganisms. Among these, a number of both natural and synthetic compounds have been progressively identified as able to interrupt the intercellular communication within a microbial community and the adhesion to a surface, thus disintegrating mature/preformed biofilms. This review describes the role played by QS in the formation of bacterial biofilms and then focuses on the mechanisms of different natural and synthetic QS inhibitors (QSIs) exhibiting promising antibiofilm ability against Gram-positive and Gram-negative bacterial pathogens and on their applications as biocontrol strategies in various fields. [ABSTRACT FROM AUTHOR]

Antimicrobial resistance poses a global health threat, with Staphylococcus aureus emerging as a notorious pathogen capable of forming stubborn biofilms and regulating virulence through quorum sensing (QS). In the quest for novel therapeutic strategies, this groundbreaking study unveils the therapeutic potential of Paederia foetida Linn., an Asian medicinal plant containing various bioactive compounds, contributing to its antimicrobial activities, in the battle against S. aureus. Through a comprehensive approach, we investigated the effect of ethanolic P. foetida leaf extract on S. aureus biofilms, QS, and antimicrobial activity. The extract exhibited promising inhibitory effects against S. aureus including the biofilm-forming strain and MRSA. Real-time PCR analysis revealed significant downregulation of key virulence and biofilm genes, suggesting interference with QS. Biofilm assays quantified the extract's ability to disrupt and prevent biofilm formation. LC-MS/MS analysis identified quercetin and kaempferol glycosides as potential bioactive constituents, while molecular docking studies explored their binding to the QS transcriptional regulator SarA. Computational ADMET predictions highlighted favorable intestinal absorption but potential P-glycoprotein interactions limiting oral bioavailability. While promising anti-virulence effects were demonstrated, the high molecular weights and excessive hydrogen bond donors/acceptors of the flavonoid glycosides raise concerns regarding drug-likeness and permeability. This integrated study offers valuable insights for developing novel anti-virulence strategies to combat antimicrobial resistance. [ABSTRACT FROM AUTHOR]

Simple Summary: Lactic acid bacteria (LAB) are often used to improve the probiotic content in aquaculture organisms. Although LAB were fed to aquaculture organisms, these LAB were often not detected when analyzing the gut microbiota. While the intestinal environment was indeed improved, this indicates that the effect of LAB on aquaculture organisms may not occur through the bacteria themselves, but rather through substances such as extracellular vesicles involved in these processes. This study will utilize an in vitro cultured intestinal bacteria system to exclude host interference and investigate the potential of L. reuteri-derived EVs for regulating the intestinal microbiota. Extracellular vesicles (EVs) are functional substances secreted by microbes and host cells, and it has been discovered that they participate in the interactions between different microorganisms. Our recent findings indicate that Limosilactobacillus reuteri-derived EVs have the potential to improve the intestinal microbiota of Oplegnathus fasciatus fish and inhibit pathogenic bacteria. Previous research has reported that the host intestinal cells play a regulatory role in the intestinal microbiota. This suggested that to investigate the mechanisms through which L. reuteri-derived EVs regulate the intestinal microbiota, a system that excludes interference from host intestinal cells should be established. In this study, an in vitro cultured intestinal bacteria system, without host factors, was used to simulate the intestinal microbiota of O. fasciatus fish. After adding L. reuteri-derived EVs to the system, the changes in the microbiota were analyzed. The results showed that L. reuteri-derived EVs effectively reduced the abundance of Vibrio spp. In the results of the in vitro experiments, it was also observed that L. reuteri-derived EVs have the ability to inhibit Vibrio alginolyticus. We further sequenced the small RNA contained in L. reuteri-derived EVs and found that these small RNAs can interfere with genes (LysR, pirin, MIpA/OmpV, CatB, and aspartate-semialdehyde dehydrogenase) related to the growth of V. alginolyticus. Taken together, the results indicate that in the absence of host involvement, the small RNAs present in L. reuteri-derived EVs have the function of inhibiting pathogenic bacteria and exhibit the potential to regulate the intestinal microbiota. [ABSTRACT FROM AUTHOR]

Campylobacter jejuni is the foodborne pathogen causing most gastrointestinal infections. Understanding its ability to form biofilms is crucial for devising effective control strategies in food processing environments. In this study, we investigated the growth dynamics and biofilm formation of C. jejuni NCTC 11168 in various culture media, including chicken juice (CJ), brain heart infusion (BHI), and Mueller Hinton (MH) broth. Our results demonstrated that C. jejuni exhibited a higher growth rate and enhanced biofilm formation in CJ and in 1:1 mixtures of CJ with BHI or MH broth compared to these measures in BHI or MH broth alone. Electron microscopy unveiled distinct morphological attributes of late-stage biofilm cells in CJ, including the presence of elongated spiral-shaped cells, thinner stretched structures compared to regular cells, and extended thread-like structures within the biofilms. Proteomic analysis identified significant alterations in protein expression profiles in C. jejuni biofilms, with a predominance of downregulated proteins associated with vital functions like metabolism, energy production, and amino acid and protein biosynthesis. Additionally, a significant proportion of proteins linked to biofilm formation, virulence, and iron uptake were suppressed. This shift toward a predominantly coccoid morphology echoed the reduced energy demands of these biofilm communities. Our study unlocks valuable insights into C. jejuni's biofilm in CJ, demonstrating its adaptation and survival. [ABSTRACT FROM AUTHOR]

Invasive dental procedures, such as wisdom teeth removal, have been identified as potential triggers for vascular events due to the entry of oral bacteria into the bloodstream, leading to acute vascular inflammation and endothelial dysfunction. This study presents the case of a 27-year-old healthy male who developed ischemic stroke resulting from bacteremia after undergoing wisdom teeth extraction. Initially, the patient experienced fever and malaise, which were followed by right-sided hemiplegia. Diagnostic imaging, including a CT scan, identified a subacute infarction in the posterior crus of the left internal capsule, and MRI findings indicated inflammatory changes in the masticatory muscles. Further investigations involving biopsies of the masticatory muscles, along with blood and cerebrospinal fluid samples, confirmed bacterial meningitis with associated vasculitis. Notably, oral bacteria linked to periodontitis, including Porphyromonas gingivalis, Fusobacterium nucleatum, Tannerella forsythia, and Parvimonas micra, were found in the biopsies and microbiological analyses. To the best of our knowledge, this is the first reported case showing that bacteremia following dental procedures can lead to such severe neurological outcomes. This case underscores the importance of recognizing bacteremia-induced vasculitis in patients presenting with neurological symptoms post-dental procedures, emphasizing the broader implications of oral infections in such pathologies. [ABSTRACT FROM AUTHOR]

Simple Summary: Pseudomonas donghuensis HYS has lethal virulence towards Caenorhabditis elegans. Anaerobic coproporphyrinogen III oxidase (HemN) is involved in Pseudomonas heme synthesis. However, no research thus far has examined the contribution of HemN to the virulence of Pseudomonas. There are four hemN genes in P. donghuensis HYS, and we reported for the first time that the deletion of the hemN2 gene significantly reduced the virulence of P. donghuensis HYS towards C. elegans. HemN2 was negatively regulated by the Gac system and regulated bacterial virulence via 7-hydroxytropolone (7-HT) synthesis and redox levels. Our findings revealed the key role of HemN2 in bacterial virulence, which may help us to better understand the strong pathogenicity of the genus Pseudomonas. Compared to pathogens Pseudomonas aeruginosa and P. putida, P. donghuensis HYS has stronger virulence towards Caenorhabditis elegans. However, the underlying mechanisms haven't been fully understood. The heme synthesis system is essential for Pseudomonas virulence, and former studies of HemN have focused on the synthesis of heme, while the relationship between HemN and Pseudomonas virulence were barely pursued. In this study, we hypothesized that hemN2 deficiency affected 7-hydroxytropolone (7-HT) biosynthesis and redox levels, thereby reducing bacterial virulence. There are four hemN genes in P. donghuensis HYS, and we reported for the first time that deletion of hemN2 significantly reduced the virulence of HYS towards C. elegans, whereas the reduction in virulence by the other three genes was not significant. Interestingly, hemN2 deletion significantly reduced colonization of P. donghuensis HYS in the gut of C. elegans. Further studies showed that HemN2 was regulated by GacS and participated in the virulence of P. donghuensis HYS towards C. elegans by mediating the synthesis of the virulence factor 7-HT. In addition, HemN2 and GacS regulated the virulence of P. donghuensis HYS by affecting antioxidant capacity and nitrative stress. In short, the findings that HemN2 was regulated by the Gac system and that it was involved in bacterial virulence via regulating 7-HT synthesis and redox levels were reported for the first time. These insights may enlighten further understanding of HemN-based virulence in the genus Pseudomonas. [ABSTRACT FROM AUTHOR]

Bacteriophages (phages) are viruses that infect the bacteria within which their reproduction cycle takes place, a process that ends in the lysis and death of the bacterial cell. Some phages are also able to destroy bacterial biofilms. Due to increased antibiotics resistance, Pseudomonas aeruginosa, another biofilm-forming pathogen, is a problem in many parts of the world. Zinc oxide (ZnO) and other metal nanoparticles (NPs) are biologically active and also possess anti-biofilm properties. ZnO-NPs were prepared by the green synthesis method using orange peels. The vibrational peaks of the ZnO-NPs were analyzed using FTIR analysis, and their size and morphological properties were determined using scanning electron microscopy (SEM). The ability of the ZnO-NPs to reduce or eliminate P. aeruginosa biofilm alone or in combination with phages PB10 and PA19 was investigated. The P. aeruginosa cells were effectively killed in the preformed 48 h biofilms during a 24 h incubation with the ZnO-NP–phage combination, in comparison with the control or ZnO-NPs alone. The treatments on growing biofilms were most efficient in the final stages of biofilm development. All five treatment groups showed a significant biofilm reduction compared to the control group (p < 0.0001) at 48 h of incubation. The influence of the ZnO-NPs and phages on the quorum sensing system of P. aeruginosa was monitored by quantitative real-time PCR (qRT-PCR) of the autoinducer biosynthesis gene lasI. While the ZnO-NPs repressed the lasI gene transcription, the phages slightly activated it at 24 and 48 h of incubation. Also, the effect of the ZnO-NPs and phage PA19 on the viability of HFF2 cells was investigated and the results showed that the combination of NPs with PA19 reduced the toxic effect of ZnO-NPs and also stimulated the growth in normal cells. [ABSTRACT FROM AUTHOR]

Fusarium pseudograminearum causes destructive crown disease in wheat. The velvet protein family is a crucial regulator in development, virulence, and secondary metabolism of fungi. We conducted a functional analysis of FpVelB using a gene replacement strategy. The deletion of FpVelB decreased radial growth and enhanced conidial production compared to that of wild type. Furthermore, FpVelB modulates the fungal responses to abiotic stress through diverse mechanisms. Significantly, virulence decreased after the deletion of FpVelB in both the stem base and head of wheat. Genome-wide gene expression profiling revealed that the regulation of genes by FpVelB is associated with several processes related to the aforementioned phenotype, including "immune", "membrane", and "antioxidant activity", particularly with regard to secondary metabolites. Most importantly, we demonstrated that FpVelB regulates pathogen virulence by influencing deoxynivalenol production and modulating the expression of the PKS11 gene. In conclusion, FpVelB is crucial for plant growth, asexual development, and abiotic stress response and is essential for full virulence via secondary metabolism in F. pseudograminearum. [ABSTRACT FROM AUTHOR]

Many enzymes in the Raetz pathway for lipid A biosynthesis in Escherichia coli are essential. A homologous protein Pa1792|LpxH in Pseudomonas aeruginosa is known to complement the loss of LpxH in E. coli. Genome-wide transposon-insertion sequencing analysis indicates that lpxH is essential in P. aeruginosa. However, genetic analysis of lpxH in P. aeruginosa has not been carried out, partly because the conditional alleles of essential genes are not readily constructed. In this study, we first constructed a plasmid-based temperature-sensitive mutant ΔlpxH/pTS-lpxH or lpxH(Ts) in P. aeruginosa PAO1. Spot-plating assay indicated that lpxH(Ts) was lethal at a restrictive temperature, confirming its essentiality for growth. Microscopic analysis revealed that lpxH(Ts) exhibited an oval-shaped morphology, suggesting that lpxH was required for rod-shape formation. SDS-PAGE and Western blotting analysis showed that lpxH(Ts) failed to synthesize lipid A, consistent with its function in lipid A biosynthesis. Strong expression of lpxH but not the non-homologous isoenzyme lpxI or lpxG impeded growth and caused cell lysis, implying that lpxH-specific cofactors were required for this toxic effect in P. aeruginosa. Together, our results demonstrate that lpxH is essential for lipid A biosynthesis, rod-shaped growth, and viability in P. aeruginosa. We propose that this plasmid-based conditional allele is a useful tool for the genetic study of essential genes in P. aeruginosa. [ABSTRACT FROM AUTHOR]

Pseudomonas aeruginosa is a pathogen that causes healthcare-associated infections (HAIs) worldwide. It is unclear whether P. aeruginosa isolated from the natural environment has the same pathogenicity and antimicrobial resistance potential as clinical strains. In this study, virulence- and resistance-associated genes were compared in 14 genomic sequences of clinical and environmental isolates of P. aeruginosa using the VFDB, PATRIC, and CARD databases. All isolates were found to share 62% of virulence genes related to adhesion, motility, secretion systems, and quorum sensing and 72.9% of resistance genes related to efflux pumps and membrane permeability. Our results indicate that both types of isolates possess conserved genetic information associated with virulence and resistance mechanisms regardless of the source. However, none of the environmental isolates were associated with high-risk clones (HRCs). These clones (ST235 and ST111) were found only in clinical isolates, which have an impact on human medical epidemiology due to their ability to spread and persist, indicating a correlation between the clinical environment and increased virulence. The genomic variation and antibiotic susceptibility of environmental isolates of P. aeruginosa suggest potential biotechnological applications if obtained from sources that are under surveillance and investigation to limit the emergence and spread of antibiotic resistant strains [ABSTRACT FROM AUTHOR]

With the rising demand for medical implants and the dominance of implant-associated failures including infections, extensive research has been prompted into the development of novel biomaterials that can offer desirable characteristics. This study develops and evaluates new titanium-based alloys containing gallium additions with the aim of offering beneficial antibacterial properties while having a reduced stiffness level to minimise the effect of stress shielding when in contact with bone. The focus is on the microstructure, mechanical properties, antimicrobial activity, and cytocompatibility to inform the suitability of the designed alloys as biometals. Novel Ti-33Nb-xGa alloys (x = 3, 5 wt%) were produced via casting followed by homogenisation treatment, where all results were compared to the currently employed alloy Ti-6Al-4V. Optical microscopy, scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS) results depicted a single beta (β) phase microstructure in both Ga-containing alloys, where Ti-33Nb-5Ga was also dominated by dendritic alpha (α) phase grains in a β-phase matrix. EDS analysis indicated that the α-phase dendrites in Ti-33Nb-5Ga were enriched with titanium, while the β-phase was richer in niobium and gallium elements. Mechanical properties were measured using nanoindentation and microhardness methods, where the Young's modulus for Ti-33Nb-3Ga and Ti-33Nb-5Ga was found to be 75.4 ± 2.4 and 67.2 ± 1.6 GPa, respectively, a significant reduction of 37% and 44% with respect to Ti-6Al-4V. This reduction helps address the disproportionate Young's modulus between titanium implant components and cortical bone. Importantly, both alloys successfully achieved superior antimicrobial properties against Gram-negative P. aeruginosa and Gram-positive S. aureus bacteria. Antibacterial efficacy was noted at up to 90 ± 5% for the 3 wt% alloy and 95 ± 3% for the 5 wt% alloy. These findings signify a substantial enhancement of the antimicrobial performance when compared to Ti-6Al-4V which exhibited very small rates (up to 6.3 ± 1.5%). No cytotoxicity was observed in hGF cell lines over 24 h. Cell morphology and cytoskeleton distribution appeared to depict typical morphology with a prominent nucleus, elongated fibroblastic spindle-shaped morphology, and F-actin filamentous stress fibres in a well-defined structure of parallel bundles along the cellular axis. The developed alloys in this work have shown very promising results and are suggested to be further examined towards the use of orthopaedic implant components. [ABSTRACT FROM AUTHOR]

Listeria monocytogenes, a foodborne pathogen causing listeriosis, poses substantial societal, economic, and public health challenges due to its resistance, persistence, and biofilm formation in the food industry. Exploring subinhibitory concentrations of compounds to target virulence inhibition and increase susceptibility to adverse conditions presents a promising strategy to mitigate its impact of L. monocytogenes and unveils new potential applications. Thus, this study aims to explore the effect of linalool on virulence factors of L. monocytogenes and potential use in the reduction in its tolerance to stressful conditions. This action was analysed considering the use of two sub-inhibitory concentrations of linalool, 0.312 and 0.625 mg/mL. We found that even with the lowest tested concentrations, a 65% inhibition of violacein production by Chromobacterium violaceum, 55% inhibition in biofilm formation by L. monocytogenes and 62% reduction on haemolysis caused by this bacterium were observed. In addition to its impact on virulence factors, linalool diminished the tolerance to osmotic stress (up to 4.3 log reduction after 24 h with 12% NaCl), as well as to high (up to 3.8 log reduction after 15 min at 55 °C) and low temperatures (up to 4.6 log reduction after 84 days with 12% NaCl at 4 °C). Thus, this study paves the way to further investigation into the potential utilization of linalool to mitigate the threat posed by L. monocytogenes in the field of food safety and public health. [ABSTRACT FROM AUTHOR]

Pseudomonas aeruginosa (PA) is an opportunistic pathogen frequently isolated from cutaneous chronic wounds. How PA, in the presence of oxidative stress (OS), colonizes chronic wounds and forms a biofilm is still unknown. The purpose of this study is to investigate the changes in gene expression seen when PA is challenged with the high levels of OS present in chronic wounds. We used a biofilm-forming PA strain isolated from the chronic wounds of our murine model (RPA) and performed a qPCR to obtain gene expression patterns as RPA developed a biofilm in vitro in the presence of high levels of OS, and then compared the findings in vivo, in our mouse model of chronic wounds. We found that the planktonic bacteria under OS conditions overexpressed quorum sensing genes that are important for the bacteria to communicate with each other, antioxidant stress genes important to reduce OS in the microenvironment for survival, biofilm formation genes and virulence genes. Additionally, we performed RNAseq in vivo and identified the activation of novel genes/pathways of the Type VI Secretion System (T6SS) involved in RPA pathogenicity. In conclusion, RPA appears to survive the high OS microenvironment in chronic wounds and colonizes these wounds by turning on virulence, biofilm-forming and survival genes. These findings reveal pathways that may be promising targets for new therapies aimed at disrupting PA-containing biofilms immediately after debridement to facilitate the treatment of chronic human wounds. [ABSTRACT FROM AUTHOR]

More sustainable biosensor production is growing in importance, allowing for the development of technological solutions for several industries, such as those in the health, chemical, and food sectors. Tracking the latest advancements in biosensors' scientific production is fundamental to determining the opportunities for the future of the biosensing field. This article aims to map scientific production in the biosensors field by running a bibliometric analysis of journal articles registered in the Web of Science database under biosensor-related vital concepts. The key concepts were selected by researchers and biosensor technology developers working on the BioAssembler Horizon project. The findings lead to identifying the scientific and technological knowledge base on biosensing devices and tracking the main scientific organisations developing this technology throughout the COVID-19 period (2019–2023). The institutional origin of the publications characterised the global distribution of related knowledge competencies and research partnerships. These results are discussed, shedding light on the scientific, economic, political, and structural factors that contribute to the formation of a scientific knowledge-based focus on the performance and design of these sensors. Moreover, the lack of scientific ties between the three axes of organisations producing expertise in this area (China, USA, and Russia) points towards the need to find synergies through new mechanisms of co-authorship and collaboration. [ABSTRACT FROM AUTHOR]

Due to the resistance of Gram-negative bacteria Pseudomonas aeruginosa PAO1 to most clinically relevant antimicrobials, the use of traditional antibiotic treatments in hospitals is challenging. The formation of biofilms, which is regulated by the quorum-sensing (QS) system of Pseudomonas aeruginosa (PA), is an important cause of drug resistance. There are three main QS systems in P. aeruginosa: the las system, the rhl system, and the pqs system. The inhibitors of the las system are the most studied. Previously, the compound AOZ-1 was found to have a certain inhibitory effect on the las system when screened. In this study, twenty-four compounds were designed and synthesized by modifying the Linker and Rings of AOZ-1. Using C. violaceum CV026 as a reporter strain, this study first assessed the inhibitory effects of new compounds against QS, and their SAR was investigated. Then, based on the SAR analysis of compound AOZ-1 derivatives, the parent core of AOZ-1 was replaced to explore the structural diversity. Then, nine new compounds were designed and synthesized with a new nucleus core component of 3-amino-tetrahydro-l,3-oxazin-2-one. The compound Y-31 (IC50 = 91.55 ± 3.35 µM) was found to inhibit the QS of C. violaceum CV026. Its inhibitory effect on C. violaceum CV026 was better than that of compound AOZ-1 (IC50 > 200 µM). Furthermore, biofilm formation is one of the important causes of Pseudomonas aeruginosa PAO1 resistance. In this study, it was found that compound Y-31, with a new nucleus core component of 3-amino-tetrahydro-l,3-oxazin-2-one, had the highest biofilm inhibition rate (40.44%). The compound Y-31 has a certain inhibitory effect on the production of PAO1 virulence factors (pyocyanin, rhamnolipid, and elastase) and swarming. When the concentration of compound Y-31 was 162.5 µM, the inhibition rates of pyocyanin, rhamnolipid, and elastase were 22.48%, 6.13%, and 22.67%, respectively. In vivo, the lifetime of wildtype Caenorhabditis elegans N2 infected with P. aeruginosa PAO1 was markedly extended by the new parent nucleus Y-31. This study also performed cytotoxicity experiments and in vivo pharmacokinetics experiments on the compound Y-31. In conclusion, this study identified a compound, Y-31, with a new nucleus core component of 3-amino-tetrahydro-l,3-oxazin-2-one, which is a potential agent for treating P. aeruginosa PAO1 that is resistant to antibiotics and offers a way to discover novel antibacterial medications. [ABSTRACT FROM AUTHOR]

This article discusses the molecular mechanisms of bacterial communication and their role in biocontrol. Bacteria are social organisms that engage in cooperative and competitive interactions, which are crucial for their survival. These interactions are supported by bacterial communication, which involves the exchange of signals between cells. Signals can be diverse, but they are generally small diffusible molecules that cross cell membranes and freely diffuse through the environment. Bacteria use communication systems to evaluate their density and synchronize their behavior, such as in biofilm formation. However, communication can be disrupted by other organisms, and strategies to quench bacterial communication are being developed for biocontrol purposes. [Extracted from the article]

Bacillus velezensis FZB42 is a plant growth-promoting rhizobacterium (PGPR) and a model microorganism for biofilm studies. Biofilms are required for the colonization and promotion of plant growth in the rhizosphere. However, little is known about how the final stage of the biofilm life cycle is regulated, when cells regain their motility and escape the mature biofilm to spread and colonize new niches. In this study, the non-annotated gene ccdC was found to be involved in the process of biofilm dispersion. We found that the ccdC-deficient strain maintained a wrinkled state at the late stage of biofilm formation in the liquid—gas interface culture, and the bottom solution showed a clear state, indicating that no bacterial cells actively escaped, which was further evidenced by the formation of a cellular ring (biofilm pellicle) located on top of the preformed biofilm. It can be concluded that dispersal, a biofilm property that relies on motility proficiency, is also positively affected by the unannotated gene ccdC. Furthermore, we found that the level of cyclic diguanylate (c-di-GMP) in the ccdC-deficient strain was significantly greater than that in the wild-type strain, suggesting that B. velezensis exhibits a similar mechanism by regulating the level of c-di-GMP, the master regulator of biofilm formation, dispersal, and cell motility, which controls the fitness of biofilms in Pseudomonas aeruginosain. In this study, we investigated the mechanism regulating biofilm dispersion in PGPR. [ABSTRACT FROM AUTHOR]

Histoplasma capsulatum causes a fungal respiratory disease. Some studies suggest that the fungus requires zinc to consolidate the infection. This study aimed to investigate the influence of zinc and the metal chelator TPEN on the growth of Histoplasma in planktonic and biofilm forms. The results showed that zinc increased the metabolic activity, cell density, and cell viability of planktonic growth. Similarly, there was an increase in biofilm metabolic activity but no increase in biomass or extracellular matrix production. N′-N,N,N,N–tetrakis–2-pyridylmethylethane–1,2 diamine (TPEN) dramatically reduced the same parameters in the planktonic form and resulted in a decrease in metabolic activity, biomass, and extracellular matrix production for the biofilm form. Therefore, the unprecedented observations in this study highlight the importance of zinc ions for the growth, development, and proliferation of H. capsulatum cells and provide new insights into the role of metal ions for biofilm formation in the dimorphic fungus Histoplasma, which could be a potential therapeutic strategy. [ABSTRACT FROM AUTHOR]