The biofilm matrix: multitasking in a shared space

Metal-phenolic network crosslinked nanogel with prolonged biofilm retention for dihydroartemisinin/NIR synergistically enhanced chemodynamic therapy

Chemodynamic therapy (CDT) is emerging as a promising treatment for biofilm infections. However, its effectiveness is significantly hindered by several factors: the body's stable temperature, a limited supply of Fe2+ ions, and inadequate endogenous levels of H2O2 at the infection sites. Herin, our study introduces MPN-crosslinked hyaluronic acid (HA) nanogels as an effective strategy for treating biofilm-associated infections. The DHA@HA-TA/Fe (DHTF) nanogel is synthesized through the coordination reaction between Fe2+ ions and tannic acid (TA)-modified HA, with dihydroartemisinin (DHA) encapsulated within the structure. DHTF exhibits pH-/hyaluronidase-responsiveness in the biofilm infection microenvironment, enabling sustained release of DHA as a substitute for H2O2 and Fe2+ for CDT. The incorporation of Fe2+/TA-based MPN and DHA within the nanogels enables photothermal/DHA dually-enhanced CDT, facilitating efficient disruption of biofilm matrices and bacterial eradication through boosting reactive oxygen species production. In vivo studies demonstrate that DHTF exhibit prolonged retention within biofilms. This ensures a sustained release of therapeutic agents and continuous anti-biofilm activity. Eventually, both in vitro and in vivo evaluations consistently confirm the significant anti-biofilm capacity of DHTF. Our findings highlight the potential of DHTF as a promising nanomedicine for biofilm-related infections, offering efficient treatment strategies that could improve clinical management of these challenging conditions.

Characterization of Bacterial Membrane Fatty Acid Profiles for Biofilm Cells

When submitted to environmental stresses, bacteria can modulate its fatty acid composition of membrane phospholipids in order to optimize membrane fluidity. Characterization of bacterial membrane fatty acid profiles is thus an interesting indicator of cellular physiological state. The methodology described here aims to improve the recovering of biofilm cells for the characterization of their fatty acid profiles. The saponification reagent is directly applied on the whole biofilm before the removal of cells from the inert surface. In this way, maximum of the cells and their fatty acids can be recovered from the deepest layers of the biofilm.

Engineering mesoporous polydopamine-based potentiate STING pathway activation for advanced anti-biofilm therapy

The biofilm-induced "relatively immune-compromised zone" creates an immunosuppressive microenvironment that is a significant contributor to refractory infections in orthopedic endophytes. Consequently, the manipulation of immune cells to co-inhibit or co-activate signaling represents a crucial strategy for the management of biofilm. This study reports the incorporation of Mn2+ into mesoporous dopamine nanoparticles (Mnp) containing the stimulator of interferon genes (STING) pathway activator cGAMP (Mncp), and outer wrapping by M1-like macrophage cell membrane (m-Mncp). The cell membrane enhances the material's targeting ability for biofilm, allowing it to accumulate locally at the infectious focus. Furthermore, m-Mncp mechanically disrupts the biofilm through photothermal therapy and induces antigen exposure through photodynamic therapy-generated reactive oxygen species (ROS). Importantly, the modulation of immunosuppression and immune activation results in the augmentation of antigen-presenting cells (APCs) and the commencement of antigen presentation, thereby inducing biofilm-specific humoral immunity and memory responses. Additionally, this approach effectively suppresses the activation of myeloid-derived suppressor cells (MDSCs) while simultaneously boosting the activity of T cells. Our study showcases the efficacy of utilizing m-Mncp immunotherapy in conjunction with photothermal and photodynamic therapy to effectively mitigate residual and recurrent infections following the extraction of infected implants. As such, this research presents a viable alternative to traditional antibiotic treatments for biofilm that are challenging to manage.

Intrinsic antimicrobial resistance: Molecular biomaterials to combat microbial biofilms and bacterial persisters

The escalating rise in antimicrobial resistance (AMR) coupled with a declining arsenal of new antibiotics is imposing serious threats to global public health. A pervasive aspect of many acquired AMR infections is that the pathogenic microorganisms exist as biofilms, which are equipped with superior survival strategies. In addition, persistent and recalcitrant infections are seeded with bacterial persister cells at infection sites. Together, conventional antibiotic therapeutics often fail in the complete treatment of infections associated with bacterial persisters and biofilms. Novel therapeutics have been attempted to tackle AMR, biofilms, and persister-associated complex infections. This review focuses on the progress in designing molecular biomaterials and therapeutics to address acquired and intrinsic AMR, and the fundamental microbiology behind biofilms and persisters. Starting with a brief introduction of AMR basics and approaches to tackling acquired AMR, the emphasis is placed on various biomaterial approaches to combating intrinsic AMR, including (1) semi-synthetic antibiotics; (2) macromolecular or polymeric biomaterials mimicking antimicrobial peptides; (3) adjuvant effects in synergy; (4) nano-therapeutics; (5) nitric oxide-releasing antimicrobials; (6) antimicrobial hydrogels; (7) antimicrobial coatings. Particularly, the structure-activity relationship is elucidated in each category of these biomaterials. Finally, illuminating perspectives are provided for the future design of molecular biomaterials to bypass AMR and cure chronic multi-drug resistant (MDR) infections.

Global challenges and microbial biofilms: Identification of priority questions in biofilm research, innovation and policy

Priority question exercises are increasingly used to frame and set future research, innovation and development agendas. They can provide an important bridge between the discoveries, data and outputs generated by researchers, and the information required by policy makers and funders. Microbial biofilms present huge scientific, societal and economic opportunities and challenges. In order to identify key priorities that will help to advance the field, here we review questions from a pool submitted by the international biofilm research community and from practitioners working across industry, the environment and medicine. To avoid bias we used computational approaches to group questions and manage a voting and selection process. The outcome of the exercise is a set of 78 unique questions, categorized in six themes: (i) Biofilm control, disruption, prevention, management, treatment (13 questions); (ii) Resistance, persistence, tolerance, role of aggregation, immune interaction, relevance to infection (10 questions); (iii) Model systems, standards, regulatory, policy education, interdisciplinary approaches (15 questions); (iv) Polymicrobial, interactions, ecology, microbiome, phage (13 questions); (v) Clinical focus, chronic infection, detection, diagnostics (13 questions); and (vi) Matrix, lipids, capsule, metabolism, development, physiology, ecology, evolution environment, microbiome, community engineering (14 questions). The questions presented are intended to highlight opportunities, stimulate discussion and provide focus for researchers, funders and policy makers, informing future research, innovation and development strategy for biofilms and microbial communities.

Nonlinear viscoelasticity of filamentous fungal biofilms of Neurospora discreta

The picture of bacterial biofilms as a colloidal gel composed of rigid bacterial cells protected by extracellular crosslinked polymer matrix has been pivotal in understanding their ability to adapt their microstructure and viscoelasticity to environmental assaults. This work explores if an analogous perspective exists in fungal biofilms with long filamentous cells. To this end, we consider biofilms of the fungus Neurospora discreta formed on the air-liquid interface, which has shown an ability to remove excess nitrogen and phosphorous from wastewater effectively. We investigated the changes to the viscoelasticity and the microstructure of these biofilms when the biofilms uptake varying concentrations of nitrogen and phosphorous, using large amplitude oscillatory shear flow rheology (LAOS) and field-emission scanning electron microscopy (FESEM), respectively. A distinctive peak in the loss modulus (G″) at 30-50 % shear strain is observed, indicating the transition from an elastic to plastic deformation state. Though a peak in G″ has been observed in several soft materials, including bacterial biofilms, it has eluded interpretation in terms of quantifiable microstructural features. The central finding of this work is that the intensity of the G″ peak, signifying resistance to large deformations, correlates directly with the protein and polysaccharide concentrations per unit biomass in the extracellular matrix and inversely with the shear-induced changes in filament orientation in the hyphal network. These correlations have implications for the rational design of fungal biofilms with tuneable mechanical properties.

Dual osmotic controlled release platform for antibiotics to overcome antimicrobial-resistant infections and promote wound healing

Methicillin-Resistant Staphylococcus aureus forming into biofilms can trigger chronic inflammation and disrupt skin wound healing processes. Prolonged and excessive use of antibiotics can expedite the development of resistance, primarily because of their limited ability to penetrate microbial membranes and biofilms, especially antibiotics with intracellular drug targets. Herein, we devise a strategy in which virus-inspired nanoparticles control the release of antibiotics through rapid penetration into both bacterial cells and biofilms, thereby combating antimicrobial-resistant infections and promoting skin wound healing. Lipid-based nanoparticles based on stearamine and cholesterol were designed to mimic viral highly ordered nanostructures. To mimic the arginine-rich fragments in viral protein transduction domains, the primary amines on the surface of the lipid-based nanoparticles were exchanged by guanidine segments. Levofloxacin, an antibiotic that inhibits DNA replication, was chosen as the model drug to be incorporated into nanoparticles. Hyaluronic acid was coated on the surface of nanoparticles acting as a capping agent to achieve bacterial-specific degradation and guanidine explosion in the bacterial microenvironment. Our virus-inspired nanoparticles displayed long-acting antibacterial effects and powerful biofilm elimination to overcome antimicrobial-resistant infections and promote skin wound healing. This work demonstrates the ability of virus-inspired nanoparticles to achieve a dual penetration of microbial cell membranes and biofilm structures to address antimicrobial-resistant infections and trigger skin wound healing.

Microbial biofilms as a platform for diverse biocatalytic applications

Microbial biofilms have gained significant traction in commercial wastewater treatment due to their inherent resilience, well-organized structure, and potential for collaborative metabolic processes. As our understanding of their physiology deepens, these living catalysts are finding exciting applications beyond wastewater treatment, including the production of bulk and fine chemicals, bioelectricity generation, and enzyme immobilization. While the biological applications of biofilms in different biocatalytic systems have been extensively summarized, the applications of artificially engineered biofilms were rarely discussed. This review aims to bridge this gap by highlighting the untapped potential of engineered microbial biofilms in diverse biocatalytic applications, with a focus on strategies for biofilms engineering. Strategies for engineering biofilm-based systems will be explored, including genetic modification, synthetic biology approaches, and targeted manipulation of biofilm formation processes. Finally, the review will address key challenges and future directions in developing robust biofilm-based biocatalytic platforms for large-scale production of chemicals, pharmaceuticals, and biofuels.

Revealing the regulatory impact of nutrient on the production of (R)-2-(4-Hydroxyphenoxy)propanoic acid by Beauveria bassiana biofilms through comparative transcriptomics analyse

Carbon and nitrogen play a fundamental role in the architecture of fungal biofilm morphology and metabolite production. However, the regulatory mechanism of nutrients remains to be fully understood. In this study, the formation of Beauveria bassiana biofilm and the production of (R)-2-(4-Hydroxyphenoxy)propanoic acid in two media with different carbon and nitrogen sources (GY: Glucose as a carbon source and yeast extract as a nitrogen source, MT: Mannitol as a carbon source and tryptone as a nitrogen source) were compared. R-HPPA production increased 2.85-fold in media MT than in media GY. Different fungal biofilm morphology and architecture were discovered in media GY and MT. Comparative transcriptomics revealed up-regulation of mitogen-activated protein kinase (MAPK) pathway and polysaccharides degradation genes affecting mycelial morphology and polysaccharides yield of the extracellular polymeric substances (EPS) in MT medium biofilms. Upregulation of genes related to NADH synthesis (carbon metabolism, amino acid metabolism, glutamate cycle) causes NADH accumulation and triggers an increase in R-HPPA production. These data provide a valuable basis for future studies on regulating fungal biofilm morphology and improving the production of high-value compounds.

Sources, interactions, influencing factors and ecological risks of microplastics and antibiotic resistance genes in soil: A review

Microplastics (MPs) and antibiotic resistance genes (ARGs) are gaining increasing attention as they pose a threat to the ecological environment and human health as emerging contaminants. MPs has been proved to be a hot spot in ARGs, and although it has been extensively studied in water environment, the results of bibliometrics statistical analysis in this paper showed that relevant studies in soil ecological environment are currently in the initial stage. In view of this, the paper provides a systematic review of the sources, interactions, influencing factors, and ecological risks associated with MPs and ARGs in soil environments. Additionally, the mechanism and influencing factors of plastisphere formation and resistance are elaborated in detail. The MPs properties, soil physicochemical properties, soil environmental factors and agricultural activities are the primarily factors affecting the interaction between MPs and ARGs in soil. Challenges and development directions of related research in the future are also prospected. It is hoped that the review could assist in a deeper comprehension and exploration of the interaction mechanism between MPs and ARGs in soil as well as the function of MPs in the transmission process of ARGs among diverse environmental media and organisms, and provide theory basis and reference for the MPs and ARGs pollution control and remediation in soil.

Mass transfer in heterogeneous biofilms: Key issues in biofilm reactors and AI-driven performance prediction

Biofilm reactors, known for utilizing biofilm formation for cell immobilization, offer enhanced biomass concentration and operational stability over traditional planktonic systems. However, the dense nature of biofilms poses challenges for substrate accessibility to cells and the efficient release of products, making mass transfer efficiency a critical issue in these systems. Recent advancements have unveiled the intricate, heterogeneous architecture of biofilms, contradicting the earlier view of them as uniform, porous structures with consistent mass transfer properties. In this review, we explore six biofilm reactor configurations and their potential combinations, emphasizing how the spatial arrangement of biofilms within reactors influences mass transfer efficiency and overall reactor performance. Furthermore, we discuss how to apply artificial intelligence in processing biofilm measurement data and predicting reactor performance. This review highlights the role of biofilm reactors in environmental and energy sectors, paving the way for future innovations in biofilm-based technologies and their broader applications.

Encapsulation nanoarchitectonics of glabridin with sophorolipid micelles for addressing biofilm hazards via extracellular polymeric substance permeation and srtA gene suppression

BACKGROUND

Biofilm, a common drug-resistant phenotype of Staphylococcus aureus (S. aureus), demonstrates significant drug resistance and recurrence due to its extracellular polymeric substance (EPS) barrier and subsequent bacterial migration. Hence, there is an urgent need for effective solutions to mitigate the hazards posed by biofilms.

RESULT

This study developed a stable, low-toxicity multifunctional nanomicelle, GLA@SOL/EYL, by encapsulating glabridin (GLA) using sophorolipid (SOL) and egg yolk lecithin (EYL). Optimizations were performed for the hydration medium, the ratio of carrier materials to GLA, and EYL additions. GLA@SOL/EYL exhibited a particle size of 122.1 ± 0.8 nm and a surface potential of -66.4 ± 1.7 mV, endowing it with the ability to permeate biofilms EPS effectively. GLA@SOL/EYL encapsulated 98.3 ± 1.2 % of GLA and demonstrated a slow-release effect, significantly enhancing the bioavailability of GLA. The addition of EYL reduced the hemolytic toxicity of GLA@SOL/EYL and improved its encapsulation rate and stability. GLA@SOL/EYL reduced the minimum inhibitory concentration of GLA to 8 μg/mL and extended its inhibitory effect at low concentrations by rapidly disrupting the structural integrity of S. aureus. GLA@SOL/EYL may penetrate biofilms to disperse EPS and remove twice as much biofilm as GLA alone, thereby eliminating 99.99 % of S. aureus within biofilms, compared to 99 % bactericidal efficacy of GLA. Additionally, GLA@SOL/EYL inhibited 63.8 ± 1.8 % of biofilm formation by affecting the expression of the srtA gene, thereby reducing the expression of cell wall-anchoring protein genes. In contrast, the biofilm inhibition rates of GLA and blank micelles were less than 10 %.

CONCLUSION

GLA@SOL/EYL utilizes the nanoparticle effect to penetrate biofilms and deliver antimicrobial GLA. The SOL disperses the biofilm matrix while GLA is released to kill S. aureus, preventing bacterial dissemination and colonization. Thus, GLA@SOL/EYL presents an innovative strategy for effectively eradicating S. aureus biofilms and preventing new hazards in a one-step approach.

Variation in heat resistance and biofilm formation of Bacillus cereus spores in various fermented soybean foods

This study investigated the heat resistance of Bacillus cereus spores (as well as spores in intact biofilm) in two types of Korean fermented soybean foods and presumed the potential key parameters (physicochemical and nutritional properties) associated with their heat resistance. For example, the D100°C-values of B. cereus ATCC 10987 and CH3 spores with strong heat resistance and prolific biofilm-forming capability were compared in various Jjigae-type (Cheonggukjang jjigae, Doenjang jjigae, and Gochujang jjigae) and Jang-type (Cheonggukjang, Doenjang, and Gochujang) foods commonly consumed in Korea. The D100°C-values of planktonic spores were significantly different depending on the type of food, that is, Jang and Jjigae. Compared with Jjigae-type foods, a higher heat resistance of B. cereus spores was found in Jang-type foods (particularly Doenjang and Gochujang) with low water activity and high salinity. In Jjigae-type foods, spore heat resistance showed a positive correlation with the pH of Jjigaes, indicating that an acidic environment weakens the spores. A negative correlation between the total fat content and spore heat resistance was found in Jjigae-type foods but not in Jang-type foods. Meanwhile, regarding the heat resistance of B. cereus spores in intact biofilm, the D100°C-values were significantly higher (up to 6.5-fold) than those of planktonic spores in all Jjigae-type foods. The slightly acidic pH and amount of carbohydrates are likely related to the large formation of extracellular polymeric substances and strong heat resistance of B. cereus spores in biofilm. This study may provide a comprehensive understanding of the relationship between the key parameters of foods and heat resistance of B. cereus spores with or without intact biofilm and methods to control their risks in different types of fermented soybean foods.

Antimicrobial and antibiotic-potentiating effect of calcium peroxide nanoparticles on oral bacterial biofilms

Bacterial biofilms represent a prominent biological barrier against physical and chemical attacks. Disturbing the anaerobic microenvironment within biofilms by co-delivery of oxygen appears as a promising strategy to enhance the activity of an antibiotic. Here, we report the effect of oxygen-producing calcium peroxide nanoparticles (CaO2 NP) in combination with tobramycin sulfate (Tob). On Pseudomonas aeruginosa PAO1 biofilms in vitro, the additive effect of CaO2 NP towards Tob activity enhanced biofilm eradication by 2 log compared to Tob alone. For natural biofilms grown in the oral cavity of human volunteers in situ, treatment by CaO2 NP alone slightly increased the fraction of dead bacteria from 44% in various controls, including Tob alone, to 57%. However, the combination of CaO2 NP with Tob further increased the fraction of dead bacteria to 69%. These data confirm the intrinsic antimicrobial and antibiotic-potentiating effect of CaO2 NP also in a clinically relevant setting.

Real-time high-resolution microscopy reveals how single-cell lysis shapes biofilm matrix morphogenesis

During development, multiscale patterning requires that cells organize their behavior in space and time. Bacteria in biofilms must similarly dynamically pattern their behavior with a simpler toolkit. Like in eukaryotes, morphogenesis of the extracellular matrix is essential for biofilm development, but how it is patterned has remained unclear. Here, we explain how the architecture of eDNA, a key matrix component, is controlled by single cell lysis events during Pseudomonas aeruginosa biofilm development. We extend single-cell imaging methods to capture complete biofilm development, characterizing the stages of biofilm development and visualizing eDNA matrix morphogenesis. Mapping the spatiotemporal distribution of single cell lysis events reveals that cell lysis is restricted to a specific biofilm zone. Simulations indicate that this patterning couples cell lysis to growth, more uniformly distributing eDNA throughout the biofilm. Finally, we find that patterning of cell lysis is organized by nutrient gradients that act as positioning cues.

Nanozyme-Shelled Microcapsules for Targeting Biofilm Infections in Confined Spaces

Bacterial infections in irregular and branched confinements pose significant therapeutic challenges. Despite their high antimicrobial efficacy, enzyme-mimicking nanoparticles (nanozymes) face difficulties in achieving localized catalysis at distant infection sites within confined spaces. Incorporating nanozymes into microrobots enables the delivery of catalytic agents to hard-to-reach areas, but poor nanoparticle dispersibility and distribution during fabrication hinder their catalytic performance. To address these challenges, a nanozyme-shelled microrobotic platform is introduced using magnetic microcapsules with collective and adaptive mobility for automated navigation and localized catalysis within complex confinements. Using double emulsions produced from microfluidics as templates, iron oxide and silica nanoparticles are assembled into 100-µm microcapsules, which self-organize into multi-unit, millimeter-size assemblies under rotating magnetic fields. These microcapsules exhibit high peroxidase-like activity, efficiently catalyzing hydrogen peroxide to generate reactive oxygen species (ROS). Notably, microcapsule assemblies display remarkable collective navigation within arched and branched confinements, reaching the targeted apical regions of the tooth canal with high accuracy. Furthermore, these nanozyme-shelled microrobots perform rapid catalysis in situ and effectively kill biofilms on contact via ROS generation, enabling localized antibiofilm action. This study demonstrates a facile method of integrating nanozymes onto a versatile microrobotic platform to address current needs for targeted therapeutic catalysis in complex and confined microenvironments.

Holliday junction resolvase RuvC targets biofilm eDNA and confers plant resistance to vascular pathogens

A biofilm lifestyle is critical for bacterial pathogens to colonize and protect themselves from host immunity and antimicrobial chemicals in plants and animals. The formation and regulation mechanisms of phytobacterial biofilm are still obscure. Here we found that the protein Ralstonia solanacearum resistance to ultraviolet C (RuvC) is highly abundant in biofilm and positively regulates pathogenicity by controlling systemic movement in tomato xylem. RuvC protein accumulates at the later stage of biofilm development and specifically targets Holliday junction (HJ)-like structures to disrupt the biofilm extracellular DNA (eDNA) lattice, thus facilitating biofilm dispersal. Recombinant RuvC protein can resolve extracellular HJ to prevent bacterial biofilm formation. Heterologous expression of R. solanacearum or Xanthomonas oryzae pv. oryzae RuvC with plant secretion signal in tomato or rice confers resistance to bacterial wilt or bacterial blight disease, respectively. Plant chloroplast-localized HJ resolvase monokaryotic chloroplast 1 (MOC1), which shares structural similarity with bacterial RuvC, shows a strong inhibitory effect on bacterial biofilm formation. Relocalization of SlMOC1 to apoplast in tomato roots leads to increased resistance to bacterial wilt. Our novel finding reveals a critical pathogenesis mechanism of R. solanacearum and provides an efficient biotechnology strategy to improve plant resistance to bacterial vascular disease.

Bacterial biofilm-mediated environmental remediation: Navigating strategies to attain Sustainable Development Goals

Bacterial biofilm is a structured bacterial community enclosed within a three-dimensional polymeric matrix, governed by complex signaling pathways, including two-component systems, quorum sensing, and c-di-GMP, which regulate its development and resistance in challenging environments. The genetic configurations within biofilm empower bacteria to exhibit significant pollutant remediation abilities, offering a promising strategy to tackle diverse ecological challenges and expedite progress toward Sustainable Development Goals (SDGs). Biofilm-based technologies offer advantages such as high treatment efficiency, cost-effectiveness, and sustainability compared to conventional methods. They significantly contribute to agricultural improvement, soil fertility, nutrient cycling, and carbon sequestration, thereby supporting SDG 1 (No poverty), SDG 2 (Zero hunger), SDG 13 (Climate action), and SDG 15 (Life on land). In addition, biofilm facilitates the degradation of organic-inorganic pollutants from contaminated environments, aligning with SDG 6 (Clean water and sanitation) and SDG 14 (Life below water). Bacterial biofilm also has potential applications in industrial innovation, aligning SDG 7 (Affordable and clean energy), SDG 8 (Decent work and economic growth), and SDG 9 (Industry, innovation, and infrastructure). Besides, bacterial biofilm prevents several diseases, aligning with SDG 3 (Good health and well-being). Thus, bacterial biofilm-mediated remediation provides advanced opportunities for addressing environmental issues and progressing toward achieving the SDGs. This review explores the potential of bacterial biofilms in addressing soil pollution, wastewater, air quality improvement, and biodiversity conservation, emphasizing their critical role in promoting sustainable development.

Spatiotemporally Guided Single-Atom Bionanozyme for Targeted Antibiofilm Treatment

The heterogeneous and dynamic microenvironment of biofilms complicates bacterial infection treatment. Nanozyme catalytic therapy has recently been promising in treating biofilm infections. However, active nanozymes designed with the required precision targeting the biofilm microenvironment are lacking. This work proposes a spatiotemporally guided single-atom bionanozyme (BioSAzyme) for targeted antibiofilm therapy based on protein engineering of copper single-atom nanozyme (Cu SAzyme). The Cu SAzyme, synthesized via a novel mechanochemistry-assisted method, features highly accessible Cu-N4 active sites exposed on 2D N-doped carbon, exhibiting excellent triple enzyme-like activities according to experimental results and density functional theory calculations. Inheriting biofunctionality from both glucose oxidase and concanavalin A, BioSAzyme can localize the biofilm glycocalyx and catalyze endogenous glucose into H₂O₂ and gluconic acid, thus triggering multiplex cascade reactions with pH self-adaption to consume glucose and glutathione and generate •OH radicals. This spatiotemporally guided bionanocatalytic agent effectively inhibits E. coli O157: H7 and methicillin-resistant S. aureus biofilms in vitro and in vivo. Taking together, this work opens up new avenues for the rational design of single-atom nanozymes for precise antibiofilm therapy.

Investigation of the impact of widely used pesticides on conjugative transfer of multidrug resistance plasmids

Plasmid-mediated conjugative transfer has emerged as a major driver accounting for the dissemination of antibiotic resistance genes (ARGs). In addition to the use of antimicrobial agents, there is growing evidence that non-antibiotic factors also play an important role. Pesticides are widely used to protect crops against vectors of diseases, and are indispensable agents in agricultural production, whereas the impact of pesticide pollution on the transmission of antimicrobial resistance remains poorly understood. Here we reveal that the pesticides at environmentally relevant concentrations, especially cyromazine (Cyr) and kresoxim-methyl (Kre), greatly facilitate the conjugative transfer of antibiotic-resistance plasmids carrying clinically important ARGs. Mechanistic studies indicate that Cyr and Kre treatments trigger reactive oxygen species (ROS) production and SOS response, increase membrane permeability, upregulate bacterial proton motive force (PMF) and promote ATP supply. Further non-targeted metabolomics and biochemical analysis demonstrate that the addition of Cyr and Kre accelerates tricarboxylic acid (TCA) cycle and electron transport chain (ETC), thereby activating bacterial energy metabolism. In the constructed soil model, we prove that two pesticides contribute to the dissemination of resistance plasmids in the soil microbiota. 16S rRNA sequencing analyses indicate that pesticides alter transconjugant microbial communities, and enable more opportunistic pathogens, such as Pseudomonas and Enterobacter, to acquire the multidrug resistance plasmids. Collectively, our work indicates the potential risk in accelerating the spread of antimicrobial resistance owing to pesticide pollution, highlighting the importance of continuous surveillance of pesticide residues in complex environmental settings.

The role of exopolysaccharides Psl and Pel in resistance of Pseudomonas aeruginosa to the oxidative stressors sodium hypochlorite and hydrogen peroxide

Pseudomonas aeruginosa is well-known for its antimicrobial resistance and the ability to survive in harsh environmental conditions due to an abundance of resistance mechanisms, including the formation of biofilms and the production of exopolysaccharides. Exopolysaccharides are among the major components of the extracellular matrix in biofilms and aggregates of P. aeruginosa. Although their contribution to antibiotic resistance has been previously shown, their roles in resistance to oxidative stressors remain largely elusive. Here, we studied the function of the exopolysaccharides Psl and Pel in the resistance of P. aeruginosa to the commonly used disinfectants and strong oxidizing agents NaOCl and H2O2. We observed that the simultaneous inactivation of Psl and Pel in P. aeruginosa PAO1 mutant strain ∆pslA pelF resulted in a significant increase in susceptibility to both NaOCl and H2O2. Further analyses revealed that Pel is more important for oxidative stress resistance in P. aeruginosa and that the form of Pel (i.e., cell-associated or cell-free) did not affect NaOCl susceptibility. Additionally, we show that Psl/Pel-negative strains are protected against oxidative stress in co-culture biofilms with P. aeruginosa PAO1 WT. Taken together, our results demonstrate that the EPS matrix and, more specifically, Pel exhibit protective functions against oxidative stressors such as NaOCl and H2O2 in P. aeruginosa.

IMPORTANCE

Biofilms are microbial communities of cells embedded in a self-produced polymeric matrix composed of polysaccharides, proteins, lipids, and extracellular DNA. Biofilm bacteria have been shown to possess unique characteristics, including increased stress resistance and higher antimicrobial tolerance, leading to failures in bacterial eradication during chronic infections or in technical settings, including drinking and wastewater industries. Previous studies have shown that in addition to conferring structure and stability to biofilms, the polysaccharides Psl and Pel are also involved in antibiotic resistance. This work provides evidence that these biofilm matrix components also contribute to the resistance of Pseudomonas aeruginosa to oxidative stressors including the widely used disinfectant NaOCl. Understanding the mechanisms by which bacteria escape antimicrobial agents, including strong oxidants, is urgently needed in the fight against antimicrobial resistance and will help in developing new strategies to eliminate resistant strains in any environmental, industrial, and clinical setting.

Mechanisms of oral microflora in Parkinson's disease

Parkinson's disease (PD) is a common neurodegenerative disease with complex pathogenesis and no effective treatment. Recent studies have shown that dysbiosis of the oral microflora is closely related to the development of PD. The abnormally distributed oral microflora of PD patients cause degenerative damage and necrosis of dopamine neurons by releasing their own components and metabolites, intervening in the oral-gut-brain axis, crossing the biofilm, inducing iron dysregulation, activating inter-microflora interactions, and through the mediation of saliva,ultimately influencing the development of the disease. This article reviews the structure of oral microflora in patients with PD, the mechanism of development of PD caused by oral microflora, and the potential value of targeting oral microflora in developing a new strategy for PD prevention, diagnosis and treatment.

Mechanisms of antimicrobial resistance in biofilms

Most bacteria in nature exist in aggregated communities known as biofilms, and cells within a biofilm demonstrate major physiological changes compared to their planktonic counterparts. Biofilms are associated with many different types of infections which can have severe impacts on patients. Infections involving a biofilm component are often chronic and highly recalcitrant to antibiotic therapy as a result of intrinsic physical factors including extracellular matrix production, low growth rates, altered antibiotic target production and efficient exchange of resistance genes. This review describes the biofilm lifecycle, phenotypic characteristics of a biofilm, and contribution of matrix and persister cells to biofilms intrinsic tolerance to antimicrobials. We also describe how biofilms can evolve antibiotic resistance and transfer resistance genes within biofilms. Multispecies biofilms and the impacts of various interactions, including cooperation and competition, between species on tolerance to antimicrobials in polymicrobial biofilm communities are also discussed.

Spiky Magnetic Microparticles Synthesized from Microrod-Stabilized Pickering Emulsion

Tailoring the microstructure of magnetic microparticles is of vital importance for their applications. Spiky magnetic particles, such as those made from sunflower pollens, have shown promise in single cell treatment and biofilm removal. Synthetic methods that can replicate or extend the functionality of such spiky particles would be advantageous for their widespread utilization. In this work, a wet-chemical method is introduced for spiky magnetic particles that are templated from microrod-stabilized Pickering emulsions. The spiky morphology is generated by the upright attachment of silica microrods at the oil-water interface of oil droplets. Spiky magnetic microparticles with control over the length of the spikes are obtained by dispersing hydrophobic magnetic nanoparticles in the oil phase and photopolymerizing the monomer. The spiky morphology dramatically enhances colloidal stability of these particles in high ionic strength solutions and physiologic media such as human saliva and saline-based biofilm suspension. To demonstrate their utility, the spiky magnetic particles are applied for magnetically controlled removal of oral biofilms and retrieval of bacteria for diagnostic sampling. This method expands the toolbox for engineering microparticle morphology and could promote the fabrication of functional magnetic microrobots.

Rethinking characterization, application, and importance of extracellular polymeric substances in water technologies

Biofilms play important roles in water technologies such as membrane treatments and activated sludge. The extracellular polymeric substances (EPS) are key components of biofilms. However, the precise nature of these substances and how they influence biofilm formation and behavior remain critical knowledge gaps. EPS are produced by many different microorganisms and span multiple biopolymer classes, which each require distinct strategies for characterization. The biopolymers additionally associate with each other to form insoluble complexes. Here, we explore recent progress toward resolving the structures and functions of EPS, where a shift towards direct functional assessments and advanced characterization techniques is necessary. This will enable integration with better microbial community and omics analyses to understand EPS biosynthesis pathways and create further opportunities for EPS control and valorization.

Nicotine promotes pathogenic bacterial growth and biofilm formation in peri-implant

Introduction. Peri-implantitis is a plaque-associated disease that leads to implant loss and arises from bacterial biofilms on the surface of the implant. Smoking is a risk factor for peri-implantitis and impedes treatment effectiveness. Additionally, aryl hydrocarbon receptor (AHR), IL-6, and IL-22 levels are related to peri-implantitis.Aim. We aimed to investigate the effects of nicotine on inflammatory response, bacterial growth and biofilm formation.Hypothesis/Gap Statement. We hypothesized that nicotine promoted pathogenic bacterial growth and biofilm formation, thereby aggravating inflammation.Methodology. The expression of AHR, IL-6 and IL-22 was measured in peri-implant sulci fluid using quantitative PCR and Western blot analyses. The cementum was incubated with bacterial suspension including Porphyromonas gingivalis, Streptococcus sanguinis and Fusobacterium nucleatum and treated with 100, 200, 250 and 300 µg ml-1 nicotine, and then, the absorbance and number of colony-forming units were detected. Biofilm formation was evaluated using the tissue culture plate method and safranin O staining. Carbohydrates and proteins were measured by the phenol-sulfuric acid method and the bicinchoninic acid method, respectively.Results. The results indicated that smoking increased the levels of AHR, IL-6 and IL-22. Functionally, nicotine promoted the growth of P. gingivalis, S. sanguinis and F. nucleatum. Additionally, it promoted the biofilm formation of these bacteria and increased the contents of carbohydrates and proteins.Conclusion. Nicotine promoted bacterial growth and biofilm build-up, suggesting that smoking may aggravate the progression of peri-implantitis.

Dual tobramycin and docosahexaenoic acid loaded nanoemulsions combating Pseudomonas aeruginosa-induced pulmonary infection

Pseudomonas aeruginosa (P. aeruginosa) typically forms biofilms in vivo, which exhibit high resistance and complicate eradication efforts. Additionally, persistent inflammation and excessive oxidative stress can lead to severe lung dysfunction, facilitating bacterial colonization and infection. Herein, we prepared oil-in-water (O/W) nanoemulsions (TD-αT NEs) by using PEG5k-block-PCL5k and α-tocopherol to encapsulate tobramycin (TOB). To enhance TOB's drug load, a hydrophobic ion pair (TDIP) composed of TOB and docosahexaenoic acid (DHA) was pre-prepared. TD-αT NEs was not only easily prepared and aerosolized, but stable in both physics and chemistry. The negatively charged TD-αT NEs facilitated penetration through mucus, reaching infection sites. Subsequently, TD-αT NEs permeated biofilms due to their small size and released drugs via lipase-triggered carrier dissociation, aiding in eradicating internal bacteria within biofilms (with a 16-fold reduction in CFU vs. free TOB group). TD-αT NEs simultaneously exerted superior anti-inflammatory effects, reducing levels of pro-inflammatory cytokines (NO, IL-6, IL-8, and TNF-α) while increasing the level of anti-inflammatory cytokine (IL-10). It was achieved through the upregulation of PPAR-γ and downregulation of NF-κB signaling, thus mitigating the lung damage. In addition, TD-αT NEs demonstrated strong antioxidant activity, alleviating the oxidative stress induced by P. aeruginosa. Notably, when administered via inhalation, TD-αT NEs significantly reduced the lung bacterial burden, lung inflammation, and oxidative stress in vivo compared to TOB solution. TD-αT NEs could prove beneficial in treating chronic pulmonary infections induced by P. aeruginosa through a comprehensive strategy, specifically enhancing biofilm eradication, reducing inflammation, and alleviating oxidative stress.

How bacteria actively use passive physics to make biofilms

Modern molecular microbiology elucidates the organizational principles of bacterial biofilms via detailed examination of the interplay between signaling and gene regulation. A complementary biophysical approach studies the mesoscopic dependencies at the cellular and multicellular levels with a distinct focus on intercellular forces and mechanical properties of whole biofilms. Here, motivated by recent advances in biofilm research and in other, seemingly unrelated fields of biology and physics, we propose a perspective that links the biofilm, a dynamic multicellular organism, with the physical processes occurring in the extracellular milieu. Using Bacillus subtilis as an illustrative model organism, we specifically demonstrate how such a rationale explains biofilm architecture, differentiation, communication, and stress responses such as desiccation tolerance, metabolism, and physiology across multiple scales-from matrix proteins and polysaccharides to macroscopic wrinkles and water-filled channels.

Dual-species biofilm of Streptococcus mutans and Candida albicans produces subsurface caries lesions on bovine enamel

OBJECTIVES

To develop a protocol for forming subsurface caries lesions on bovine enamel by dual-species biofilms of Streptococcus mutans and Candida albicans in vitro.

DESIGN

Biofilms were grown on bovine enamel specimens in artificial saliva (AS) for seven days. After 24 h of formation, the AS was supplemented or not with fluoride (F) using sodium fluoride (0.005 or 0.008 ppm F), and the biofilms were exposed or not to a 20 % sucrose solution (reproducing a cariogenic challenge) once/day. On the seventh day, the biofilms were harvested and had their extracellular polysaccharides (EPS) and inorganic components analyzed. The specimens were subjected to computed X-ray microtomography analysis to determine their mineral concentration. Data were compared using two-way analyses of variance, followed by Fisher's LSD or Student-Newman-Keuls tests (p < 0.05).

RESULTS

Biofilms exposed to the cariogenic challenge had significantly higher EPS concentrations than those not exposed, regardless of the presence of F. For biofilms grown with 0.008 ppm F, those exposed to the cariogenic challenge had lower F levels than those not exposed. For biofilms exposed to the cariogenic challenge, those grown with 0.008 ppm F had lower lesion depths and integrated mineral loss, and higher outer layers than those grown without F.

CONCLUSIONS

The dual biofilm model assessed was able to create subsurface caries lesions in bovine enamel in vitro, which was influenced by the presence of F in the culture medium and exposure to sucrose.

Marine-derived bioactive materials as antibiofilm and antivirulence agents

Microbial infections are major human health issues, and, recently, the mortality rate owing to bacterial and fungal infections has been increasing. In addition to intrinsic and extrinsic antimicrobial resistance mechanisms, biofilm formation is a key adaptive resistance mechanism. Several bioactive compounds from marine organisms have been identified for use in biofilm therapy owing to their structural complexity, biocompatibility, and economic viability. In this review, we discuss recent trends in the application of marine natural compounds, marine-bioinspired nanomaterials, and marine polymer conjugates as possible therapeutic agents for controlling biofilms and virulence factors. We also comprehensively discuss the mechanisms underlying biofilm formation and inhibition of virulence factors by marine-derived materials and propose possible applications of novel and effective antibiofilm and antivirulence agents.

Bioemulsifier from sponge-associated bacteria reduces staphylococcal biofilm

Biofilm formation is a major health concern and studies have been pursued to find compounds able to prevent biofilm establishment and remove pre-existing biofilms. While biosurfactants (BS) have been well-known for possessing antibiofilm activities, bioemulsifiers (BE) are still scarcely explored for this purpose. The present study aimed to evaluate the bioemulsifying properties of cell-free supernatants produced by Bacillaceae and Vibrio strains isolated from marine sponges and investigate their antiadhesive and antibiofilm activities against different pathogenic Gram-positive and Gram-negative bacteria. The BE production by the marine strains was confirmed by the emulsion test, drop-collapsing, oil-displacement, cell hydrophobicity and hemolysis assays. Notably, Bacillus cereus 64BHI1101 displayed remarkable emulsifying activity and the ultrastructure analysis of its BE extract (BE64-1) revealed the presence of structures typically observed in macromolecules composed of polysaccharides and proteins. BE64-1 showed notable antiadhesive and antibiofilm activities against Staphylococcus aureus, with a reduction of adherence of up to 100 % and a dispersion of biofilm of 80 %, without affecting its growth. BE64-1 also showed inhibition of Staphylococcus epidermidis and Escherichia coli biofilm formation and adhesion. Thus, this study provides a starting point for exploring the antiadhesive and antibiofilm activities of BE from sponge-associated bacteria, which could serve as a valuable tool for future research to combat S. aureus biofilms.

Trash into Treasure: Nano-coating of Catheter Utilizes Urine to Deprive H2S Against Persister and Rip Biofilm Matrix

Bacteria-derived hydrogen sulfide (H2S) often contributes to the emergence of antibiotic-recalcitrant bacteria, especially persister (a sub-population of dormant bacteria), thus causing the treatment failure of Catheter-associated urinary tract infection (CAUTI). Here, an H2S harvester nanosystem to prevent the generation of persister bacteria and disrupt the dense biofilm matrix by the self-adaptive ability of shape-morphing is prepared. The nanosystem possesses a core-shell structure that is composed of liquid metal nanoparticle (LM NP), AgNPs, and immobilized urease. The nanosystem decomposes urea contained in urine to generate ammonia for eliminating bacteria-derived H2S. Depending on the oxidative layer of liquid metal, the nanosystem also constitutes a long-lasting reservoir for temporarily storing bacteria-derived H2S, when urease transiently overloads or in the absence of urine in a catheter. Depriving H2S can prevent the emergence of persistent bacteria, enhancing the bacteria-killing efficiency of Ga3+ and Ag+ ions. Even when the biofilm has formed, the urine flow provides heat to trigger shape morphing of the LM NP, tearing the biofilm matrix. Collectively, this strategy can turn trash (urea) into treasure (H2S scavengers and biofilm rippers), and provides a new direction for the antibacterial materials application in the medical field.

Thermothelomyces thermophilus exo- and endo-glucanases as tools for pathogenic E. coli biofilm degradation

The escalating prevalence of drug-resistant pathogens not only jeopardizes the effectiveness of existing treatments but also increases the complexity and severity of infectious diseases. Escherichia coli is one the most common pathogens across all healthcare-associated infections. Enzymatic treatment of bacterial biofilms, targeting extracellular polymeric substances (EPS), can be used for EPS degradation and consequent increase in susceptibility of pathogenic bacteria to antibiotics. Here, we characterized three recombinant cellulases from Thermothelomyces thermophilus: a cellobiohydrolase I (TthCel7A), an endoglucanase (TthCel7B), and a cellobiohydrolase II (TthCel6A) as tools for hydrolysis of E. coli and Gluconacetobacter hansenii biofilms. Using a design mixture approach, we optimized the composition of cellulases, enhancing their synergistic activity to degrade the biofilms and significantly reducing the enzymatic dosage. In line with the crystalline and ordered structure of bacterial cellulose, the mixture of exo-glucanases (0.5 TthCel7A:0.5 TthCel6A) is effective in the hydrolysis of G. hansenii biofilm. Meanwhile, a mixture of exo- and endo-glucanases is required for the eradication of E. coli 042 and clinical E. coli biofilms with significantly different proportions of the enzymes (0.56 TthCel7B:0.44 TthCel6A and 0.6 TthCel7A:0.4 TthCel7B, respectively). X-ray diffraction pattern and crystallinity index of E. coli cellulose are comparable to those of carboxymethyl cellulose (CMC) substrate. Our results illustrate the complexity of E. coli biofilms and show that successful hydrolysis is achieved by a specific combination of cellulases, with consistent recurrence of TthCel7B endoglucanase.

Microbial extracellular polymeric substances in the environment, technology and medicine

Microbial biofilms exhibit a self-produced matrix of extracellular polymeric substances (EPS), including polysaccharides, proteins, extracellular DNA and lipids. EPS promote interactions of the biofilm with other cells and sorption of organics, metals and chemical pollutants, and they facilitate cell adhesion at interfaces and ensure matrix cohesion. EPS have roles in various natural environments, such as soils, sediments and marine habitats. In addition, EPS are relevant in technical environments, such as wastewater and drinking water treatment facilities, and water distribution systems, and they contribute to biofouling and microbially influenced corrosion. In medicine, EPS protect pathogens within the biofilm against the host immune system and antimicrobials, and emerging evidence suggests that EPS can represent potential virulence factors. By contrast, EPS yield a wide range of valuable products that include their role in self-repairing concrete. In this Review, we aim to explore EPS as a functional unit of biofilms in the environment, in technology and in medicine.

High-Sensitivity Analysis of Native Bacterial Biofilms Using Dynamic Nuclear Polarization-Enhanced Solid-State NMR

Bacterial biofilms cause persistent infections that are difficult to treat and contribute greatly to antimicrobial resistance. However, high-resolution structural information on native bacterial biofilms remain very limited. This limitation is primarily due to methodological constraints associated with analyzing complex native samples. Although solid-state NMR (ssNMR) is a promising method in this regard, its conventional applications typically suffer from sensitivity limitations, particularly for unlabeled native samples. Through the use of Dynamic Nuclear Polarization (DNP), we applied sensitivity enhanced ssNMR to characterize native Pseudomonas fluorescens colony biofilms. The increased ssNMR sensitivity by DNP enabled ultrafast structural characterization of the biofilm samples without isotope-labelling, and chemical or physical modification. We collected 1D 13 C and 15 N, and 2D 1 H- 13 C, 1 H- 15 N and 13 C- 13 C ssNMR spectra within seconds/minutes or hours, respectively which enabled us to identify biofilm components as polysaccharides, proteins, and eDNA effectively. This study represents the first application of ultrasensitive DNP ssNMR to characterize a native bacterial biofilm and expands the technical scope of ssNMR towards obtaining insights into the composition and structure of a wide array of in vitro and ex vivo biofilm applications. Such versatility should greatly boost efforts to develop structure-guided approaches for combating infections caused by biofilm-forming microbes.

Green nanotechnology in phytosynthesis and its efficiency in inhibiting bacterial biofilm formation: implications for medicine

Nanotechnology is used in several biomedical applications, including antimicrobial and antibiofilm applications using nanomaterials. Bacterial biofilm varies according to the strain; the matrix is very strong and resistant. In this sense, phytosynthesis is an important method for combating bacterial biofilms through the use of metallic nanoparticles (silver, gold, or copper) with increased marketing and technical-scientific potential. In this review, we seek to gather the leading publications on the use of phytosynthesized metallic nanoparticles against bacterial biofilms. Furthermore, this study aims to understand the main characteristics and parameters of these nanomaterials, their antibiofilm efficiency, and the presence or absence of cytotoxicity in these developed technologies.

Coacervate Dense Phase Displaces Surface-Established Pseudomonas aeruginosa Biofilms

For millions of years, barnacles and mussels have successfully adhered to wet rocks near tide-swept seashores. While the chemistry and mechanics of their underwater adhesives are being thoroughly investigated, an overlooked aspect of marine organismal adhesion is their ability to remove underlying biofilms from rocks and prepare clean surfaces before the deposition of adhesive anchors. Herein, we demonstrate that nonionic, coacervating synthetic polymers that mimic the physicochemical features of marine underwater adhesives remove ∼99% of Pseudomonas aeruginosa (P. aeruginosa) biofilm biomass from underwater surfaces. The efficiency of biofilm removal appears to align with the compositional differences between various bacterial biofilms. In addition, the surface energy influences the ability of the polymer to displace the biofilm, with biofilm removal efficiency decreasing for surfaces with lower surface energies. These synthetic polymers weaken the biofilm-surface interactions and exert shear stress to fracture the biofilms grown on surfaces with diverse surface energies. Since bacterial biofilms are 1000-fold more tolerant to common antimicrobial agents and pose immense health and economic risks, we anticipate that our unconventional approach inspired by marine underwater adhesion will open a new paradigm in creating antibiofilm agents that target the interfacial and viscoelastic properties of established bacterial biofilms.

Dispersal of a dominant competitor can drive multispecies coexistence in biofilms

Despite competition for both space and nutrients, bacterial species often coexist within structured, surface-attached communities termed biofilms. While these communities play important, widespread roles in ecosystems and are agents of human infection, understanding how multiple bacterial species assemble to form these communities and what physical processes underpin the composition of multispecies biofilms remains an active area of research. Using a model three-species community composed of Pseudomonas aeruginosa, Escherichia coli, and Enterococcus faecalis, we show with cellular-scale resolution that biased dispersal of the dominant community member, P. aeruginosa, prevents competitive exclusion from occurring, leading to the coexistence of the three species. A P. aeruginosa bqsS deletion mutant no longer undergoes periodic mass dispersal, leading to the local competitive exclusion of E. coli. Introducing periodic, asymmetric dispersal behavior into minimal models, parameterized by only maximal growth rate and local density, supports the intuition that biased dispersal of an otherwise dominant competitor can permit coexistence generally. Colonization experiments show that WT P. aeruginosa is superior at colonizing new areas, in comparison to ΔbqsS P. aeruginosa, but at the cost of decreased local competitive ability against E. coli and E. faecalis. Overall, our experiments document how one species' modulation of a competition-dispersal-colonization trade-off can go on to influence the stability of multispecies coexistence in spatially structured ecosystems.

Antimicrobial and antibiofilm properties of procyanidins: potential for clinical and biotechnological applications

Procyanidins (PCs) have emerged as agents with potential antimicrobial and antibiofilm activities, although their mechanisms of action and structure-activity relationships remain poorly understood. This review assessed the potential mechanisms of action and applications of these compounds to explore these aspects. Studies on the antimicrobial properties of PCs suggest that they are involved in osmotic imbalance, DNA interactions and metabolic disruption. Although less studied, their antibiofilm activities include antiadhesive effects and the modulation of mobility and quorum sensing. However, most research has used uncharacterized plant extracts for in vitro assays, limiting the understanding of the structure-activity relationships of PCs and their in vivo mechanisms. Clinical trials on the antimicrobial and antibiofilm properties of PCs have not clarified these issues due to nonstandardized methodologies, inadequate chemical characterization, and the limited number of studies, preventing a consensus and evaluation of the in vivo effects. Additionally, patent analysis revealed that technological developments in the antimicrobial and antibiofilm uses of PCs are concentrated in health care and dental care, but new biotechnological uses are emerging. Therefore, while PCs are promising antimicrobial and antibiofilm compounds, further research into their chemical structures and mechanisms of action is crucial for evidence-based applications in biotechnology and health care.

Anti-biofilm and antibacterial effect of bacteriocin derived from Lactobacillus plantarum on the multidrug-resistant Acinetobacter baumannii

This research examines the impact of bacteriocin derived from Lactobacillus plantarum PTCC 1745 on the biofilm formations of A. baumannii isolates. Bacteriocin derived from L. plantarum PTCC 1745 was obtained through ammonium sulfate precipitation, cation-exchange chromatography, and reversed-phase high-performance liquid chromatography (RP-HPLC). Testing for bacteriocin susceptibility has been conducted using the broth dilution method. The anti-biofilm activity of bacteriocin was evaluated using a microtiter plate method. Quantitative real-time PCR assay evaluated bap gene expression in bacteriocin-treated cells. According to SDS-PAGE, bacteriocin from L. plantarum has a 25-kDa apparent molecular weight. The MICs of bacteriocin ranged from 30 to 120 μg/mL, while the MBCs varied between 60 and 120 μg/mL. Compared to the non-treated group, strains bacteriocin-treated isolates had 59 % less ability to form biofilm. The mean relative expression of the bap gene among the MDR A. baumannii isolates decreased by 52 % compared to the untreated control. This study demonstrated that bacteriocin derived from L. plantarum PTCC 1745 had antibacterial and antibiofilm activity against MDR A. baumannii isolates.

Double-Wing Motif Protein is a Novel Biofilm Regulatory Factor of the Plant Disease Biocontrol Agent, Bacillus subtilis

Transposon mutagenesis screening of Bacillus subtilis YB-1471, a novel rhizosphere biocontrol agent of Fusarium crown rot (FCR) of wheat, resulted in the identification of orf04391, linked to reduced biofilm formation. The gene encodes a protein possessing a putative tertiary structure of a "double-wing" DNA-binding domain. Expression of orf04391 increased during biofilm development in stationary cultures and during rapid growth in shaking cultures. An orf04391 deletion strain showed reduced biofilm production related to lower levels of the extracellular matrix, and the mutant also had reduced sporulation, adhesion, root colonization, and FCR biocontrol efficiency. Transcriptome analysis of YB-1471 and Δorf04391 in stationary culture showed that the loss of orf04391 resulted in altered expression of numerous genes, including sinI, an initiator of biofilm formation. DNA binding was shown with his-tagged Orf04391 binding to the sinIR operon in vivo and in vitro. Orf04391 appears to be a transcriptional regulator of biofilm formation in B. subtilis through the Spo0A-SinI/SinR pathway.

Insights into the genomic and phenotypic characteristics of Bacillus spp. strains isolated from biofilms in broiler farms

The characterization of surface microbiota living in biofilms within livestock buildings has been relatively unexplored, despite its potential impact on animal health. To enhance our understanding of these microbial communities, we characterized 11 spore-forming strains isolated from two commercial broiler chicken farms. Sequencing of the strains revealed them to belong to three species Bacillus velezensis, Bacillus subtilis, and Bacillus licheniformis. Genomic analysis revealed the presence of antimicrobial resistance genes and genes associated with antimicrobial secretion specific to each species. We conducted a comprehensive characterization of the biofilm formed by these strains under various conditions, and we revealed significant structural heterogeneity across the different strains. A macro-colony interaction model was employed to assess the compatibility of these strains to coexist in mixed biofilms. We identified highly competitive B. velezensis strains, which cannot coexist with other Bacillus spp. Using confocal laser scanning microscopy along with a specific dye for extracellular DNA, we uncovered the importance of extracellular DNA for the formation of B. licheniformis biofilms. Altogether, the results highlight the heterogeneity in both genome and biofilm structure among Bacillus spp. isolated from biofilms present within livestock buildings.IMPORTANCELittle is known about the microbial communities that develop on farms in direct contact with animals. Nonpathogenic strains of Bacillus velezensis, Bacillus subtilis, and Bacillus licheniformis were found in biofilm samples collected from surfaces in contact with animals. Significant genetic and phenotypic diversity was described among these Bacillus strains. The strains do not possess mobile antibiotic resistance genes in their genomes and have a strong capacity to form structured biofilms. Among these species, B. velezensis was noted for its high competitiveness compared with the other Bacillus spp. Additionally, the importance of extracellular DNA in the formation of B. licheniformis biofilms was observed. These findings provide insights for the management of these surface microbiota that can influence animal health, such as the use of competitive strains to minimize the establishment of undesirable bacteria or enzymes capable of specifically deconstructing biofilms.

Application of Single Cell Type-Derived Spheroids Generated by Using a Hanging Drop Culture Technique in Various In Vitro Disease Models: A Narrow Review

Cell culture methods are indispensable strategies for studies in biological sciences and for drug discovery and testing. Most cell cultures have been developed using two-dimensional (2D) culture methods, but three-dimensional (3D) culture techniques enable the establishment of in vitro models that replicate various pathogenic conditions and they provide valuable insights into the pathophysiology of various diseases as well as more precise results in tests for drug efficacy. However, one difficulty in the use of 3D cultures is selection of the appropriate 3D cell culture technique for the study purpose among the various techniques ranging from the simplest single cell type-derived spheroid culture to the more sophisticated organoid cultures. In the simplest single cell type-derived spheroid cultures, there are also various scaffold-assisted methods such as hydrogel-assisted cultures, biofilm-assisted cultures, particle-assisted cultures, and magnet particle-assisted cultures, as well as non-assisted methods, such as static suspension cultures, floating cultures, and hanging drop cultures. Since each method can be differently influenced by various factors such as gravity force, buoyant force, centrifugal force, and magnetic force, in addition to non-physiological scaffolds, each method has its own advantages and disadvantages, and the methods have different suitable applications. We have been focusing on the use of a hanging drop culture method for modeling various non-cancerous and cancerous diseases because this technique is affected only by gravity force and buoyant force and is thus the simplest method among the various single cell type-derived spheroid culture methods. We have found that the biological natures of spheroids generated even by the simplest method of hanging drop cultures are completely different from those of 2D cultured cells. In this review, we focus on the biological aspects of single cell type-derived spheroid culture and its applications in in vitro models for various diseases.

Shuanghuanglian volatile oil exerts antipyretic, anti-inflammatory, and antibacterial synergistic effects through multiple pathways

ETHNOPHARMACOLOGICAL RELEVANCE

Traditional Chinese Medicine (TCM) has a rich history spanning 2000 years. Shuanghuanglian, a traditional Chinese herbal formula composed of three botanicals, is primarily used to treat colds, respiratory infections (including bacterial pneumonia), and pharyngitis. Previous research has found that the volatile oil of Shuanghuanglian is crucial for its efficacy. However, there is a lack of studies investigating its mechanisms.

AIM OF THE STUDY

This study aims to explore the antibacterial and anti-inflammatory mechanisms of Shuanghuanglian volatile oil and its potential to enhance the antibacterial effects when used in conjunction with antibiotics.

METHODS

Determination of the GC-MS fingerprint of SVO using Gas Chromatography-Mass Spectrometry (GC-MS), The antibacterial effects of SVO on multidrug-resistant Klebsiella pneumoniae (MDR-KP) were assessed by detecting MIC, checkerboard method assay, time-kill curves, resistance growth curves, transcriptome sequencing analysis, scanning electron microscopy(SEM), purification, and quantitative analysis of extracellular polysaccharides(EPS). In vivo part, an MDR-KP induced mouse pneumonia model was established to evaluate the mitigating effects of SVO on mouse pneumonia, using comprehensive network pharmacology and bioinformatics to identify genes related to bacterial pneumonia and potential targets of SVO. Validation was performed through molecular docking, qPCR, and ELISA tests.

RESULTS

SVO modulates the expression of MDR-KP mRNA for wecB, wecC, murA, murD, murE, murF, inhibiting the synthesis of O-antigen polysaccharides and peptidoglycans, thereby compromising bacterial cell wall integrity and affecting the synthesis of biofilms. These actions not only exhibit antibacterial effects but also enhance antibacterial activity, restoring the sensitivity of CEF to MDR-KP. SVO suppresses the biological activity of PTGS2, reducing the production of Prostaglandin E2 (PGE2), thereby exerting antipyretic and anti-inflammatory effects, providing new insights for the development of natural non-steroidal anti-inflammatory drugs (NSAIDs).

CONCLUSIONS

Our research indicates that SVO exerts antipyretic, anti-inflammatory, and antibacterial synergistic effects through multiple pathways.

Optimization of Helicobacter pylori Biofilm Formation in In Vitro Conditions Mimicking Stomach

Helicobacter pylori is one of the most common bacterial pathogens worldwide and the main etiological agent of numerous gastric diseases. The frequency of multidrug resistance of H. pylori is growing and the leading factor related to this phenomenon is its ability to form biofilm. Therefore, the establishment of a proper model to study this structure is of critical need. In response to this, the aim of this original article is to validate conditions of the optimal biofilm development of H. pylori in monoculture and co-culture with a gastric cell line in media simulating human fluids. Using a set of culture-based and microscopic techniques, we proved that simulated transcellular fluid and simulated gastric fluid, when applied in appropriate concentrations, stimulate autoaggregation and biofilm formation of H. pylori. Additionally, using a co-culture system on semi-permeable membranes in media imitating the stomach environment, we were able to obtain a monolayer of a gastric cell line with H. pylori biofilm on its surface. We believe that the current model for H. pylori biofilm formation in monoculture and co-culture with gastric cells in media containing host-mimicking fluids will constitute a platform for the intensification of research on H. pylori biofilms in in vitro conditions that simulate the human body.

Hfq-binding small RNA PqsS regulates Pseudomonas aeruginosa pqs quorum sensing system and virulence

Pseudomonas aeruginosa is a widespread nosocomial pathogen with a significant to cause both severe planktonic acute and biofilm-related chronic infections. Small RNAs (sRNAs) are noncoding regulatory molecules that are stabilized by the RNA chaperone Hfq to trigger various virulence-related signaling pathways. Here, we identified an Hfq-binding sRNA in P. aeruginosa PAO1, PqsS, which promotes bacterial pathogenicity and pseudomonas quinolone signal quorum sensing (pqs QS) system. Specifically, PqsS enhanced acute bacterial infections by inducing host cell death and promoting rhamnolipid-regulated swarming motility. Meanwhile, PqsS reduced chronic infection traits including biofilm formation and antibiotic resistance. Moreover, PqsS repressed pqsL transcript, increasing PQS levels for pqs QS. A PQS-rich environment promoted PqsS expression, thus forming a positive feedback loop. Furthermore, we demonstrated that the PqsS interacts and destabilizes the pqsL mRNA by recruiting RNase E to drive degradation. These findings provide insights for future research on P. aeruginosa pathogenesis and targeted treatment.

Research progress on the regulatory mechanism of biofilm formation in probiotic lactic acid bacteria

Probiotic lactic acid bacteria (LAB) must undergo three key stages of testing, including food processing, storage, and gastrointestinal tract environment, their beneficial effects could exert. The biofilm formation of probiotic LAB is helpful for improving their stress resistances, survival rates, and colonization abilities under adverse environmental conditions, laying an important foundation for their probiotic effects. In this review, the formation process, the composition and function of basic components of probiotic LAB biofilm have been summarized. This review focuses on the regulatory mechanism of probiotic LAB biofilm formation. In addition, the characteristics and related mechanisms of probiotics in biofilm state have been analyzed to guide the application of probiotic LAB biofilms in the field of health and food. The biofilm formation of LAB is an extremely complex process involving multiple regulatory factors. Besides quorum sensing (QS), other regulatory factors are not yet fully understood. The probiotic LAB in biofilm state exhibit superior survival rate, adhesion performance, and immunomodulation ability, attribute to various metabolic processes, including stress response, exopolysaccharide (EPS) metabolism, amino acid and protein metabolisms, etc. The understanding about regulatory mechanism of biofilm formation of different probiotic species and strains will accelerate the development and application of probiotics products.

Essential phage component induces resistance of bacterial community

Despite extensive knowledge on phage resistance at bacterium level, the resistance of bacterial communities is still not well-understood. Given its ubiquity, it is essential to understand resistance at the community level. We performed quantitative investigations on the dynamics of phage infection in Klebsiella pneumoniae biofilms. We found that the biofilms quickly developed resistance and resumed growth. Instead of mutations, the resistance was caused by unassembled phage tail fibers released by the phage-lysed bacteria. The tail fibers degraded the bacterial capsule essential for infection and induced spreading of capsule loss in the biofilm, and tuning tail fiber and capsule levels altered the resistance. Latent infections sustained in the biofilm despite resistance, allowing stable phage-bacteria coexistence. Last, we showed that the resistance exposed vulnerabilities in the biofilm. Our findings indicate that phage lysate plays important roles in shaping phage-biofilm interactions and open more dimensions for the rational design of strategies to counter bacteria with phage.

Formation of filamentous fungal biofilms in water and the transformation of resistance to chlor(am)ine disinfection

Biofilms are composed of complex multi-species in nature, potentially threatening drinking water safety. In this work, the formation of single- and multi-species fungal biofilms formed by Aspergillus niger (A. niger) and Aspergillus flavus (A. flavus), and the inactivation of mature biofilms using chlor(am)ine were firstly investigated. Results revealed that the antagonistic interaction occurred between A. niger and A. flavus. Chloramination at 20 mg/L for 30 min achieved 74.74 % and 76.04 % inactivation of A. flavus and multi-species biofilm, which were 1.69- and 1.84-fold higher than that of chlorine at the same condition. However, no significant difference was observed in the inactivation of A. niger biofilm between chlorine and monochloramine disinfection due to the lower amount of extracellular polymeric substance produced by it (p > 0.05). The inactivation of biofilm by monochloramine fitted the Weibull model well. According to the Weibull model, the monochloramine resistance of biofilm were as follows: A. flavus > multi-species > A. niger biofilm. Besides, an increase in reactive oxygen levels, damage of cell membrane, and leakage of intracellular substances in biofilms were observed after chlor(am)ination. More intracellular polysaccharides and proteins were leaked in chloramination inactivation (p < 0.05). This study provides important implications for controlling fungal biofilm.

Lectins and polysaccharide EPS I have flow-responsive roles in the attachment and biofilm mechanics of plant pathogenic Ralstonia

Bacterial biofilm formation and attachment to hosts are mediated by carbohydrate-binding lectins, exopolysaccharides, and their interactions in the extracellular matrix (ECM). During tomato infection Ralstonia pseudosolanacearum (Rps) GMI1000 highly expresses three lectins: LecM, LecF, and LecX. The latter two are uncharacterized. We evaluated the roles in bacterial wilt disease of LecF, a fucose-binding lectin, LecX, a xylose-binding lectin, and the Rps exopolysaccharide EPS I. Interestingly, single and double lectin mutants attached to tomato roots better and formed more biofilm under static conditions in vitro. Consistent with this finding, static bacterial aggregation was suppressed by heterologous expression of lecFGMI1000 and lecXGMI1000 in other Ralstonia strains that naturally lack these lectins. Crude ECM from a ΔlecF/X double mutant was more adhesive than the wild-type ECM, and LecF and LecX increased Rps attachment to ECM. The enhanced adhesiveness of the ΔlecF/X ECM could explain the double mutant's hyper-attachment in static conditions. Unexpectedly, mutating lectins decreased Rps attachment and biofilm viscosity under shear stress, which this pathogen experiences in plant xylem. LecF, LecX, and EPS I were all essential for biofilm development in xylem fluid flowing through cellulose-coated microfluidic channels. These results suggest that under shear stress, LecF and LecX increase Rps attachment by interacting with the ECM and plant cell wall components like cellulose. In static conditions such as on root surfaces and in clogged xylem vessels, the same lectins suppress attachment to facilitate pathogen dispersal. Thus, Rps lectins have a dual biological function that depends on the physical environment.