Biofilm Structure Research Articles

Effect and mechanism of Qingre Huashi decoction on drug-resistant Helicobacter pylori.

Helicobacter pylori (HP), the most common pathogenic microorganism in the stomach, can induce inflammatory reactions in the gastric mucosa, causing chronic gastritis and even gastric cancer. HP infection affects over 4.4 billion people globally, with a worldwide infection rate of up to 50%. The multidrug resistance of HP poses a serious challenge to eradication. It has been de-monstrated that compared to bismuth quadruple therapy, Qingre Huashi decoction (QHD) combined with triple therapy exhibits comparable eradication rates but with a lower incidence of adverse reactions; in addition, QHD can directly inhibit and kill HP in vitro. To explore the effect and mechanism of QHD on clinically multidrug-resistant and strong biofilm-forming HP. In this study, 12 HP strains were isolated in vitro after biopsy during gastroscopy of HP-infected patients. In vitro, the minimum inhibitory concentration (MIC) values for clinical HP strains and biofilm quantification were determined through the E-test method and crystal violet staining, respectively. The most robust biofilm-forming strain of HP was selected, and QHD was evaluated for its inhibitory and bactericidal effects on the strain with strong biofilm formation. This assessment was performed using agar dilution, E-test, killing dynamics, and transmission electron microscopy (TEM). The study also explored the impact of QHD on antibiotic resistance in these HP strains with strong biofilm formation. Crystalline violet method, scanning electron microscopy, laser confocal scanning microscopy, and (p)ppGpp chromatographic identification were employed to evaluate the effect of QHD on biofilm in strong biofilm-forming HP strains. The effect of QHD on biofilm and efflux pump-related gene expression was evaluated by quantitative polymerase chain reaction. Non-targeted metabolomics with UHPLC-MS/MS was used to identify potential metabolic pathways and biomarkers which were different between the NC and QHD groups. HP could form biofilms of different degrees in vitro, and the intensity of formation was associated with the drug resistance of the strain. QHD had strong bacteriostatic and bactericidal effects on HP, with MICs of 32-64 mg/mL. QHD could inhibit the biofilm formation of the strong biofilm-forming HP strains, disrupt the biofilm structure, lower the accumulation of (p)ppGpp, decrease the expression of biofilm-related genes including LuxS, Spot, glup (HP1174), NapA, and CagE, and reduce the expression of efflux pump-related genes such as HP0605, HP0971, HP1327, and HP1489. Based on metabolomic analysis, QHD induced oxidative stress in HP, enhanced metabolism, and potentially inhibited relevant signaling pathways by upregulating adenosine monophosphate (AMP), thereby affecting HP growth, metabolism, and protein synthesis. QHD exerts bacteriostatic and bactericidal effects on HP, and reduces HP drug resistance by inhibiting HP biofilm formation, destroying its biofilm structure, inhibiting the expression of biofilm-related genes and efflux pump-related genes, enhancing HP metabolism, and activating AMP in HP.

Nitric Oxide‐Actuated Titanium Dioxide Janus Nanoparticles for Enhanced Multimodal Disruption of Infectious Biofilms

AbstractSonodynamic therapy (SDT) is promising for combating deep‐seated infectious diseases by generating substantial reactive oxygen species (ROS) through the profound tissue penetration capabilities of ultrasound. However, the compact protective structures of bacterial biofilms present a formidable challenge, impeding ROS efficacy. Given that ROS have a limited diffusion range and current sonosensitizers struggle to infiltrate biofilms, complete eradication of pathogenic bacteria often remains unachieved. In this study, mesoporous titanium dioxide (TiO2) nanoparticles are engineered asymmetrically coated with a thin layer of Ag and loaded with L‐arginine (LA) to construct ultrasound‐propelled nanomotors. These Ag‐TiO2‐LA Janus nanoparticles demonstrate robust self‐propulsion upon ultrasonic activation, allowing for deeper penetration into biofilm matrices and enhancing localized biofilm disruption through improved SDT outcomes. Additionally, the incorporation of Ag not only broadens TiO2’s absorption spectrum but also confers photothermal capabilities upon NIR laser excitation at 808 nm. The Ag‐TiO2‐LA nanomotor amalgamates TiO2’s sonodynamic potential with Ag's photothermal properties, forging a versatile antimicrobial agent capable of efficient biofilm penetration and a synergistic antibacterial effect when subjected to dual NIR and ultrasound stimuli. This innovative, singularly‐structured nanoparticle stands out as an effective combatant against bacterial biofilms and accelerates the healing process of infected wounds, showcasing potential for multifaceted clinical applications.

Potential risk of biofilm-forming Bacillus cereus group in fresh-cut lettuce production chain

Bacillus cereus and Bacillus thuringiensis, which belong to the B. cereus group, are widely distributed in nature and can cause food poisoning symptoms. In this study, we collected 131 isolates belonging to the B. cereus group, comprising 124B. cereus and seven B. thuringiensis isolates, from fresh-cut lettuce production chain and investigated their potential risk by analyzing genotypic (enterotoxin and emetic toxin gene profiles) and phenotypic (antibiotic susceptibility, sporulation, and biofilm formation) characteristics. Enterotoxin genes were present only in B. cereus, whereas the emetic toxin gene was not detected in any of the B. cereus isolates. All isolates were susceptible to vancomycin, which is a last resort for treating B. cereus group infection symptoms, but generally resistant to β-lactam antimicrobials, and had the ability to form spores (at an average sporulation rate of 24.6 %) and biofilms at 30 °C. Isolates that formed strong biofilms at 30 °C had a superior possibility of forming a dense biofilm by proliferating at 10 °C compared to other isolates. Additionally, confocal laser scanning microscopy (CLSM) images revealed a notable presence of spores within the submerged biofilm formed at 10 °C, and the strengthened attachment of biofilm inner cells to the substrate was further revealed through biofilm structure parameters analysis. Collectively, our study revealed the prevalence and contamination levels of B. cereus and B. thuringiensis at fresh-cut lettuce production chain and investigated their genotypic and phenotypic characteristics, aiming to provide valuable insights for the development of potential risk management strategies to ensure food safety, especially along the cold chain.

Reciprocal sharing of extracellular proteases and extracellular matrix molecules facilitates Bacillus subtilis biofilm formation.

Extracellular proteases are a class of public good that support growth of Bacillus subtilis when nutrients are in a polymeric form. Bacillus subtilis biofilm matrix molecules are another class of public good that are needed for biofilm formation and are prone to exploitation. In this study, we investigated the role of extracellular proteases in B. subtilis biofilm formation and explored interactions between different public good producer strains across various conditions. We confirmed that extracellular proteases support biofilm formation even when glutamic acid provides a freely available nitrogen source. Removal of AprE from the NCIB 3610 secretome adversely affects colony biofilm architecture, while sole induction of WprA activity into an otherwise extracellular protease-free strain is sufficient to promote wrinkle development within the colony biofilm. We found that changing the nutrient source used to support growth affected B. subtilis biofilm structure, hydrophobicity and architecture. We propose that the different phenotypes observed may be due to increased protease dependency for growth when a polymorphic protein presents the sole nitrogen source. We however cannot exclude that the phenotypic changes are due to alternative matrix molecules being made. Co-culture of biofilm matrix and extracellular protease mutants can rescue biofilm structure, yet reliance on extracellular proteases for growth influences population coexistence dynamics. Our findings highlight the intricate interplay between these two classes of public goods, providing insights into microbial social dynamics during biofilm formation across different ecological niches.

The Role of Streptococcus mutans Virulence Proteins in the Pathogenesis of Endocarditis: Mechanisms of Action and Impact on Heart Infections, A Review

Background: Streptococcus mutans, known for causing dental caries, can also lead to endocarditis, a severe heart infection involving inflammation of the heart's inner lining and valves. This study focuses on the virulence proteins of Streptococcus mutans and their role in endocarditis pathogenesis. Objective: To investigate the mechanisms of action of Streptococcus mutans virulence proteins and their impact on the development of endocarditis. Methods: A comprehensive literature review focused on the virulence factors of Streptococcus mutans, such as Glucosyltransferases (Gtf), Adhesin P1 (Antigen I/II), Dextranase, and proteolytic enzymes. The role of these proteins in bacterial adhesion, biofilm formation, and tissue invasion was analyzed. Results: Glucosyltransferases facilitate biofilm formation by synthesizing sticky glucans from sucrose, protecting bacteria, and aiding the colonization of heart valves. Adhesin P1 enables bacterial attachment to host tissues, which is crucial for initial colonization. Dextranase modifies biofilm structure, enhancing stability and resistance. Proteolytic enzymes degrade host proteins, aiding bacterial invasion and causing tissue damage. Conclusion: Streptococcus mutans employ multiple virulence proteins to adhere to, colonize, and invade heart tissues, leading to endocarditis. Understanding these mechanisms is essential for developing preventive and therapeutic strategies against this severe infection.

Enhanced degradation of methanethiol via operational pH regulation in biofilm reactor: Insight of sulfur metabolism pathways and microbial adaptation mechanism

Methanethiol (CH3SH), a typical organic sulfur pollutant, poses significant risks to both human health and ecological stability due to its high toxicity and corrosive properties. Membrane aerated biofilm reactor (MABR) has been regarded as a promising and eco-friendly solution for removing organic sulfur from wastewater. However, the oxidation of CH3SH might lead to spontaneous acidification, which might affect microbial metabolic activities to influence the CH3SH biotransformation in MABR system. This work demonstrated that operational pH regulation could effectively promote the complete conversion of CH3SH to SO42- in MABR, while the transformation efficiency was only 40.6% under uncontrolled pH condition. Meanwhile, operational pH regulation resulted in 35.2% reduction in the excessive secretion of extracellular polymeric substances, thereby building a stable biofilm structure with sufficient oxygen mass transfer to enhance the CH3SH transformation. Additionally, operational pH regulation favored the enrichment of sulfur-oxidizing microorganisms (e.g., Rhodanobacter and Rhodobacter), while the uncontrolled pH favored the proliferation of microorganisms in harsh environment (e.g., Chitinophagaceae sp. and Sphingobacteriales sp.). Moreover, operational pH regulation enhanced the expression of critical genes involved in sulfur metabolism (e.g., SELENBP1 and SoxA), accompanied with glycolysis (e.g., ppgK and pfkB) and pyruvate metabolism (e.g., ackA and aceE), which could provide sufficient energy and electron. Conversely, these gene expressions were down-regulated in pH unregulation reactor, while the microbial adaptation mechanism was activated through the enhancement of DNA replication, quorum sensing, and two-component system, enabling resistance to extreme acidic conditions. This study would provide the in-depth understanding of operational pH regulation on organic sulfur degradation and transformation in MABR system and offer novel guidance for organic sulfur removal.

Real-time biofilm detection techniques: advances and applications.

Microbial biofilms, complex assemblies enveloped in extracellular matrices, are significant contributors to various infections. Traditional in vitro biofilm characterization methods, though informative, often disrupt the biofilm structure. The need to address biofilm-related infections urgently emphasizes the importance of continuous monitoring and timely interventions. This review provides a focused examination of advancements in real-time biofilm detection techniques, specifically in electrochemical, optical and mechanical systems. The potential applications of real-time detection in managing and monitoring biofilm growth in industrial settings, preventing medical infections, comprehending biofilm dynamics and evaluating control strategies highlight the necessity for it. Crucially, the review emphasizes the importance of evaluating these methods for their accuracy and reliability in real-time biofilm detection, offering valuable insights for precise interventions across various applications.

The combined application of ultrasound and UVC have the potential to control mature Listeria monocytogenes and Bacillus subtilis biofilms

The present study aims to determine the bactericidal and disintegrating effect of ultraviolet type C treatments combined with ultrasound against biofilms of Listeria monocytogenes and Bacillus subtilis formed at different incubation periods (i.e. 24, 48, and 72 h). Treatments applied are UVC doses ranging from 60 to 360 mJ/cm2 (5–30 s) and US doses of 5–15 min, depending on the maturity of biofilms and the microorganism. Initially, we investigated the effects of UVC on planktonic cells, revealing a significantly higher lethality in L. monocytogenes compared to B. subtilis (P < 0.05). Moreover, B. subtilis demonstrated greater resistance in both its spore and vegetative forms (P < 0.05). The application of UVC on biofilms demonstrates that, as the more structured and robust the biofilm is, the more difficult it is for UVC to penetrate the biofilm structure and reach the cells that conform them, which is why higher lethality is observed in the shortest formation period (i.e. 24 h). In addition, as the UVC dose increases, microorganisms show a higher resistance to the treatment, thus showing a greater reduction in the microbial population at lower doses. The single application of ultrasound (US) manages to reduce the cell load between 1 and 4 log CFU/cm2, depending on the microorganism and exposure time. The results obtained after the combination of both technologies achieve higher lethality, 5.2 log reductions at the lowest doses (i.e. applying 5 min of US and 5 s of UVC). Furthermore, the maximum reduction possible for these experiments (≥5.6 log) is achieved in any treatment applying a 15-s UVC exposure time. Significant differences are observed (P < 0.05) as the maturity stage increases ([+Let] 24a > 48b > 72c hours). The combination of these two technologies demonstrates highly promising outcomes across all examined bacterial structures, including spores and vegetative biofilms.

Metagenomic insights into effects of carbon/nitrogen ratio on microbial community and antibiotic resistance in moving bed biofilm reactor

This study investigated the effects of carbon/nitrogen (C/N) ratio on microbial community in moving bed biofilm reactor (MBBR) using metagenomic analysis, and the dynamic changes of relevant antibiotic resistance genes (ARGs) were also analyzed. The results showed that under low C/N ratio, MBBR exhibited average removal rates of 98.41 % for ammonia nitrogen and 75.79 % for total nitrogen. Metagenomic analysis showed low C/N ratio altered the structure of biofilm and water microbiota, resulting in the detachment of bacteria such as Actinobacteria from biofilm into water. Furthermore, sulfamethazine (SMZ)-resistant bacteria and related ARGs were released into water under low C/N ratio, which lead to the increase of SMZ resistance rate to 90%. Moreover, most dominant genera are potential hosts for both nitrogen cycle related genes and ARGs. Specifically, Nitrosomonas that carried gene sul2 might be released from biofilm into water. These findings implied the risks of antibiotic resistance dissemination in MBBR under low C/N ratio.

Nanoparticle-Based Strategies for Managing Biofilm Infections in Wounds: A Comprehensive Review.

Chronic wounds containing opportunistic bacterial pathogens are a growing problem, as they are the primary cause of morbidity and mortality in developing and developed nations. Bacteria can adhere to almost every surface, forming architecturally complex communities called biofilms that are tolerant to an individual's immune response and traditional treatments. Wound dressings are a primary source and potential treatment avenue for biofilm infections, and research has recently focused on using nanoparticles with antimicrobial activity for infection control. This Review categorizes nanoparticle-based approaches into four main types, each leveraging unique mechanisms against biofilms. Metallic nanoparticles, such as silver and copper, show promising data due to their ability to disrupt bacterial cell membranes and induce oxidative stress, although their effectiveness can vary based on particle size and composition. Phototherapy-based nanoparticles, utilizing either photodynamic or photothermal therapy, offer targeted microbial destruction by generating reactive oxygen species or localized heat, respectively. However, their efficacy depends on the presence of light and oxygen, potentially limiting their use in deeper or more shielded biofilms. Nanoparticles designed to disrupt extracellular polymeric substances directly target the biofilm structure, enhancing the penetration and efficacy of antimicrobial agents. Lastly, nanoparticles that induce biofilm dispersion represent a novel strategy, aiming to weaken the biofilm's defense and restore susceptibility to antimicrobials. While each method has its advantages, the selection of an appropriate nanoparticle-based treatment depends on the specific requirements of the wound environment and the type of biofilm involved. The integration of these nanoparticles into wound dressings not only promises enhanced treatment outcomes but also offers a reduction in the overall use of antibiotics, aligning with the urgent need for innovative solutions in the fight against antibiotic-tolerant infections. The overarching objective of employing these diverse nanoparticle strategies is to replace antibiotics or substantially reduce their required dosages, providing promising avenues for biofilm infection management.

Unveiling the antifungal mechanisms of CTP, a new copper(II)-theophylline/1,10-phenanthroline complex, on drug-resistant non-albicans Candida species.

Candida species undeniably rank as the most prevalent opportunistic human fungal pathogens worldwide, with Candida albicans as the predominant representative. However, the emergence of non-albicans Candida species (NACs) has marked a significant shift, accompanied by rising incidence rates and concerning trends of antifungal resistance. The search for new strategies to combat antifungal-resistant Candida strains is of paramount importance. Recently, our research group reported the anti-Candida activity of a coordination compound containing copper(II) complexed with theophylline (theo) and 1,10-phenanthroline (phen), known as "CTP" - Cu(theo)2phen(H2O).5H2O. In the present work, we investigated the mechanisms of action of CTP against six medically relevant, antifungal-resistant NACs, including C. auris, C. glabrata, C. haemulonii, C. krusei, C. parapsilosis and C. tropicalis. CTP demonstrated significant efficacy in inhibiting mitochondrial dehydrogenases, leading to heightened intracellular reactive oxygen species production. CTP treatment resulted in substantial damage to the plasma membrane, as evidenced by the passive incorporation of propidium iodide, and induced DNA fragmentation as revealed by the TUNEL assay. Scanning electron microscopy images of post-CTP treatment NACs further illustrated profound alterations in the fungal surface morphology, including invaginations, cavitations and lysis. These surface modifications significantly impacted the ability of Candida cells to adhere to a polystyrene surface and to form robust biofilm structures. Moreover, CTP was effective in disassembling mature biofilms formed by these NACs. In conclusion, CTP represents a promising avenue for the development of novel antifungals with innovative mechanisms of action against clinically relevant NACs that are resistant to antifungals commonly used in clinical settings.

Study on the screening of marine beneficial bacteria and the inhibition of sulfate-reducing bacteria corrosion in marine oil field produced water

PurposeThe purpose of this study is to provide ideas and theoretical guidance for green, environmentally friendly and efficient “bacteriostasis with bacteria” technology.Design/methodology/approachIn this paper, a beneficial strain of bacteria was extracted and purified from marine mud. Weight-loss test, morphological observation and electrochemical test were used to systematically study the effect of sulfate-reducing bacteria (SRB)-induced corrosion inhibition on X65 steel in simulated offshore oil field production water.FindingsThe results showed that a beneficial strain was selected and identified as Vibrio alginolyticus. Under the condition of co-culture of SRB, the average corrosion rate of X65 steel was significantly reduced. In the mixed bacterial system, the surface of X65 steel samples was relatively flat, and the structure of biofilm and corrosion product film was dense. The number of corrosion pits, the average diameter and depth of corrosion pits were significantly reduced. The localized corrosion of X65 steel was significantly inhibited.Originality/valueThe complex and changing marine environment makes the corrosion problem of marine steel increasingly severe, and the microbiologically influenced corrosion (MIC) caused by SRB is particularly serious. The research and development of environmentally friendly corrosion protection technology is a long-term and difficult problem. The use of beneficial microorganisms to control MIC is a green and efficient anticorrosion measure. Compared with terrestrial microorganisms, marine microorganisms can adapt to complex environments, and their metabolites exhibit special biological activities. The use of marine beneficial bacteria can inhibit SRB activity to achieve the corrosion inhibition effect.

Removal of metronidazole using a novel ZnO–CoFe2O4@Biochar heterostructure composite in an intimately coupled photocatalysis and biodegradation system under visible light

The intimate coupling of photocatalysis and biodegradation (ICPB) technology has received much attraction because of the advantages of both photocatalytic reaction and biological treatment. In this study, ZnO–CoFe2O4@BC (ZCFC) with p-n heterojunction was prepared and used in an ICPB system to degrade metronidazole (MNZ) wastewater. The microstructure, morphology, and optical behavior of heterojunctions in ZCFC were investigated using SEM, XRD, UV–vis, FTIR, and XPS techniques. The results showed that ZCFC inherited the advantages of bamboo biochar's large pore size, and its large pore structure could provide a habitat for bacterial colonization in ICPB, thus shortening the internal mass transfer distance. The degradation of MNZ and chemical oxygen demand (COD) by the ICPB system was 86.8% and 58.5%, respectively, which was superior to single photocatalysis (72.5% for MNZ and 43.8% for COD) and single biodegradation (23.5% for MNZ and 20.1% for COD). In ICPB, photocatalysis and biodegradation showed a synergistic effect in the removal of MNZ, and the order of the major reactive oxygen species (ROS) leading to reduced toxicity of MNZ to the biofilm was •OH > h+ > O2•-. High-throughput sequencing analysis showed continuous evolution of biofilm structures in ICPB enriched a variety of functional species, among which the electroactive bacteria Alcaligenes and Brevundimonas played an important role in the degradation of MNZ. In this study, we investigated the possible mechanism of photocatalytic and microbial synergistic degradation of MNZ in the ICPB system and proposed a new technology for degrading antibiotic wastewater that combines the advantages of photocatalysis and biodegradation.

Microbial Biofilms: Features of Formation and Potential for Use in Bioelectrochemical Devices.

Microbial biofilms present one of the most widespread forms of life on Earth. The formation of microbial communities on various surfaces presents a major challenge in a variety of fields, including medicine, the food industry, shipping, etc. At the same time, this process can also be used for the benefit of humans-in bioremediation, wastewater treatment, and various biotechnological processes. The main direction of using electroactive microbial biofilms is their incorporation into the composition of biosensor and biofuel cells This review examines the fundamental knowledge acquired about the structure and formation of biofilms, the properties they have when used in bioelectrochemical devices, and the characteristics of the formation of these structures on different surfaces. Special attention is given to the potential of applying the latest advances in genetic engineering in order to improve the performance of microbial biofilm-based devices and to regulate the processes that take place within them. Finally, we highlight possible ways of dealing with the drawbacks of using biofilms in the creation of highly efficient biosensors and biofuel cells.

Biofilm microenvironment-activated multimodal therapy nanoplatform for effective anti-bacterial treatment and wound healing

Antimicrobial drug development faces challenges from bacterial resistance, biofilms, and excessive inflammation. Here, we design an intelligent nanoplatform utilizing mesoporous silica nanoparticles doped with copper ions for loading copper sulfide (DM/Cu2+-CuS). The mesoporous silica doped with tetrasulfide bonds responds to the biofilm microenvironment (BME), releasing Cu2+ions, CuS along with hydrogen sulfide (H2S) gas. The release of hydrogen sulfide within 72 h reached 793.5 µM, significantly higher than that observed with conventional small molecule donors. H2S induces macrophages polarization towards the M2 phenotype, reducing inflammation and synergistically accelerating endothelial cell proliferation and migration with Cu2+ions. In addition, H2S disrupts extracellular DNA within biofilms, synergistically photothermal enhanced peroxidase-like activity of CuS to effectively eradicate biofilms. Remarkably, DM-mediated consumption of endogenous glutathione enhances the anti-biofilm activity of H2S and improves oxygen species (ROS) destruction efficiency. The combination of photothermal therapy (PTT), chemodynamic therapy (CDT), and gas treatment achieves sterilization rates of 99.3 % and 99.6 % against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli), respectively, in vitro under 808 nm laser irradiation. Additionally, in vivo experiments demonstrate a significant biosafety and antibacterial potential. In summary, the H2S donor developed in this study exhibits enhanced biocompatibility and controlled release properties. By integrating BME-responsive gas therapy with antibacterial ions, PTT and CDT, a synergistic multimodal strategy is proposed to offer new therapeutic approaches for wound healing. Statement of significanceThe advanced DMOS/Cu2+-CuS (DMCC) multimodal therapeutic nanoplatform has been developed for the treatment of drug-resistant bacterial wound infections and has exhibited enhanced therapeutic efficacy through the synergistic effects of photothermal therapy, chemodynamic therapy, Cu2+ions, and H2S. The DMCC exhibited exceptional biocompatibility and could release CuS, Cu2+, and H2S in response to elevated concentrations of glutathione within the biofilm microenvironment. H2S effectively disrupted the biofilm structure. Meanwhile, peroxidase activity of CuS combined with GSH-mediated reduction of Cu2+ to Cu+ generated abundant hydroxyl radicals under acidic conditions, leading to efficient eradication of pathogenic bacteria. Furthermore, both H2S and Cu2+ could modulate M2 macrophages polarization and regulate immune microenvironment dynamics. These strategies collectively provided a novel approach for developing antibacterial nanomedical platforms.

Rapid enrichment of AnAOB with a novel vermiculite/tourmaline modification technology for enhanced DEAMOX process

The DEnitrifying AMmonium OXidation (DEAMOX) has been proven to be a promising process treating contaminated surface water containing ammonia and nitrate, while the enrichment of the slow-growing anammox bacteria (AnAOB) remains a challenge. In this study, a novel polyurethane-adhesion vermiculite/tourmaline (VTP) modified carrier was developed to achieve effective enrichment of AnAOB. The results demonstrated that the VTP-1 (vermiculite: tourmaline = 1:1) system exhibited the greatest performance with the total nitrogen removal efficiency reaching 87.6% and anammox contributing 63% to nitrogen removal. Scanning electron microscope analysis revealed the superior biofilm structure of the VTP-1 carrier, providing attachment for AnAOB. The addition of VTP-1 promoted the secretion of EPS (extracellular polymeric substances) by microorganisms, which increased to 85.34 mg/g VSS, contributing to the aggregation of anammox cells. The favorable substrate microenvironment created by NH4+ adsorption and NO2− supply via partial denitrification process facilitated the growth of AnAOB. The relative abundance of Candidatus Brocadia and Thauera increased from 0.04% to 0.3%–1.03% and 2.06% in the VTP-1 system, respectively. This study sheds new light on the anammox biofilm formation and provides a valid approach to initiate the DEAMOX process for low nitrogen polluted water treatment.

Beyond the double helix: the multifaceted landscape of extracellular DNA in Staphylococcus aureus biofilms.

Staphylococcus aureus forms biofilms consisting of cells embedded in a matrix made of proteins, polysaccharides, lipids, and extracellular DNA (eDNA). Biofilm-associated infections are difficult to treat and can promote antibiotic resistance, resulting in negative healthcare outcomes. eDNA within the matrix contributes to the stability, growth, and immune-evasive properties of S. aureus biofilms. eDNA is released by autolysis, which is mediated by murein hydrolases that access the cell wall via membrane pores formed by holin-like proteins. The eDNA content of S. aureus biofilms varies among individual strains and is influenced by environmental conditions, including the presence of antibiotics. eDNA plays an important role in biofilm development and structure by acting as an electrostatic net that facilitates protein-cell and cell-cell interactions. Because of eDNA's structural importance in biofilms and its ubiquitous presence among S. aureus isolates, it is a potential target for therapeutics. Treatment of biofilms with DNase can eradicate or drastically reduce them in size. Additionally, antibodies that target DNABII proteins, which bind to and stabilize eDNA, can also disperse biofilms. This review discusses the recent literature on the release, structure, and function of eDNA in S. aureus biofilms, in addition to a discussion of potential avenues for targeting eDNA for biofilm eradication.

A trans-acting sRNA SaaS targeting hilD, cheA and csgA to inhibit biofilm formation of S. Enteritidis

IntroductionSalmonella Enteritidis has brought great harm to public health, animal production and food safety worldwide. The biofilm formed by Salmonella Enteritidis plays a critical role in microbial cross-contamination. Small non-coding RNAs (sRNAs) have been demonstrated to be responsible for regulating the formation of biofilm. The sRNA SaaS has been identified previously, that promotes pathogenicity by regulating invasion and virulence factors. However, whether the SaaS is implicated in regulating biofilm formation in abiotic surfaces remains unclear. ObjectivesThis study aimed to clarify the effect of SaaS in Salmonella Enteritidis and explore the modulatory mechanism on the biofilm formation. MethodsMotility characteristics and total biomass of biofilm of test strains were investigated by the phenotypes in three soft agar plates and crystal violet staining in polystyrene microplates. Studies of microscopic structure and extracellular polymeric substances (EPS) of biofilm on solid surfaces were carried out using confocal laser scanning microscope (CLSM) and Raman spectra. Transcriptomics and proteomics were applied to analyze the changes of gene expression and EPS component. The RNA-protein pull-down and promoter–reporter β-galactosidase activity assays were employed to analyze RNA binding proteins and identify target mRNAs, respectively. ResultsSaaS inhibits biofilm formation by repressing the adhesion potential and the secretion of EPS components. Integration of transcriptomics and proteomics analysis revealed that SaaS strengthened the expression of the flagellar synthesis system and downregulated the expression of curli amyloid fibers. Furthermore, RNA-protein pull-down interactome datasets indicated that SaaS binds to Hfq (an RNA molecular chaperone protein, known as a host factor for phage Qbeta RNA replication) uniquely among 193 candidate proteins, and promoter–reporter β-galactosidase activity assay confirmed target mRNAs including hilD, cheA, and csgA. ConclusionSaaS inhibits the properties of bacterial mobility, perturbs the secretion of EPS, and contributes to the inhibition of biofilm formation by interacting with target mRNA (hilD, cheA, and csgA) through the Hfq-mediated pathway.

Critical hydrodynamic force levels for efficient removal of oral biofilms in simulated interdental spaces

ObjectivesSonic toothbrushes generate hydrodynamic shear forces for oral biofilm removal on tooth surfaces, but the effective thresholds for biofilm removal remain unexplored. This in vitro study aimed to investigate various threshold values for hydrodynamic biofilm removal in vitro.Materials and methodsA specialized test bench was designed with a known water flow field within a gap, ensuring that hydrodynamic shear forces on the wall were solely dependent on the volume flow, which was quantifiable using an integrated flow meter and proven by a computational fluid dynamics simulation. A young 20 h supragingival six-species biofilm was developed on hydroxyapatite disks (∅ 5 mm) and applied into the test bench, subjecting them to ascending force levels ranging from 0 to 135 Pa. The remaining biofilms were quantified using colony forming units (CFU) and subjected to statistical analysis through one-way ANOVA.ResultsVolume flow measures < 0.1 l/s: Error 1% of reading were established with the test bench. Untreated biofilms (0 Pa, no hydrodynamic shear forces) reached 7.7E7 CFU/harvest and differed significantly from all treated biofilm groups. CFU reductions of up to 2.3E6 were detected using 20 Pa, and reductions of two orders of magnitude were reached above wall shear forces of 45 Pa (6.9E5).ConclusionsCritical hydrodynamic force levels of at least 20 Pa appear to be necessary to have a discernible impact on initial biofilm removal.Clinical relevancePure hydrodynamic forces alone are insufficient for adequate biofilm removal. The addition of antiseptics is essential to penetrate and disrupt hydrodynamically loosened biofilm structures effectively.

Polyethyleneimine surface-modified silver-selenium nanocomposites for anti-infective treatment of wounds by disrupting biofilms

Bacterial biofilm formation is associated with the pathogenicity of pathogens and poses a serious threat to human health and clinical therapy. Complex biofilm structures provide physical barriers that inhibit antibiotic penetration and inactivate antibiotics via enzymatic breakdown. The development of biofilm-disrupting nanoparticles offers a promising strategy for combating biofilm infections. Hence, polyethyleneimine surface-modified silver-selenium nanocomposites, Ag@Se@PEI (ASP NCs), were designed for synergistic antibacterial effects by destroying bacterial biofilms to promote wound healing. The results of in vitro antimicrobial experiments showed that, ASP NCs achieved efficient antibacterial effects against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) by disrupting the formation of the bacterial biofilm, stimulating the outbreak of reactive oxygen species and destroying the integrity of bacterial cell membranes. The in-vivo bacterial infection in mice model showed that, ASP NCs further promoted wound healing and new tissue formation by reducing inflammatory factors and promoting collagen fiber formation which efficiently enhanced the antibacterial effect. Overall, ASP NCs possess low toxicity and minimal side effects, coupled with biocompatibility and efficient antibacterial properties. By disrupting biofilms and bacterial cell membranes, ASP NCs reduced inflammatory responses and accelerated the healing of infected wounds. This nanocomposite-based study offers new insights into antibacterial therapeutic strategies as potential alternatives to antibiotics for wound healing.