Facilitate Biofilm Formation Research Articles

OmpR-mediated activation of the Type Vl secretion system drives enhanced acid tolerance in Cronobacter.

Cronobacter (7 species) are prevalent foodborne pathogens with a remarkable capacity to adapt to acidic environments. This resilience enables them to persist in both food matrices and host organisms. Here we investigated the role of the 2-component system (TCS) response regulator OmpR in the acid tolerance of Cronobacter. Under acid stress, Cronobacter malonaticus (C. malonaticus) demonstrated significantly elevated expression of ompR and type VI secretion system (T6SS) genes, as well as a marked decrease in the survival of OmpR or T6SS-structure gene mutants, indicating the pivotal role of OmpR and T6SS in acid tolerance. Notably, OmpR markedly enhanced the T6SS expression by binding specifically to its promoter, and the activated T6SS expedited adaptation to acidic environments and facilitated biofilm formation, thereby aiding Cronobacter's survival under acidic conditions. Moreover, knocking out ompR in 6 additional Cronobacter species resulted in decreased T6SS expression and tolerance to acid stress than their wild-type strains, which further solidifies the widespread nature of the acid tolerance mechanism predicated on the activation of T6SS by OmpR in Cronobacter spp. A comprehensive understanding of the adaptation mechanisms employed by Cronobacter spp. in acidic conditions will provide a theoretical foundation for managing their contamination in acidic food matrices and preventing infection outbreaks in the infant gastrointestinal tract.

Computational exploration of the self-aggregation mechanisms of phenol-soluble modulins β1 and β2 in Staphylococcus aureus biofilms.

The formation of functional bacterial amyloids by phenol-soluble modulins (PSMs) in Staphylococcus aureus is a critical component of biofilm-associated infections, providing robust protective barriers against antimicrobial agents and immune defenses. Clarifying the molecular mechanisms of PSM self-assembly within the biofilm matrix is essential for developing strategies to disrupt biofilm integrity and combat biofilm-related infections. In this study, we analyzed the self-assembly dynamics of PSM-β1 and PSM-β2 by examining their folding and dimerization through long-timescale atomistic discrete molecular dynamics simulations. Our findings revealed that both peptides primarily adopt helical structures as monomers but shift to β-sheets upon dimerization. Monomeric state, PSM-β1 exhibited frequent transitions between helical and β-sheet forms, while PSM-β2 largely retained a helical structure. Upon dimerization, both peptides showed pronounced β-sheet formation around conserved C-terminal residues 21-44. Residues 21-33, largely unstructured as monomers, demonstrated strong tendencies for β-sheet formation and intermolecular interactions, underscoring their central role in the self-assembly of both peptides. Additionally, the PSM-β1 N-terminus formed β-sheets only when interacting with the C-terminus, whereas the PSM-β2 N-terminus remained helical and uninvolved in β-sheet formation. These distinct aggregation behaviors likely contribute to biofilm dynamics, with C-terminal regions facilitating biofilm formation and N-terminal regions influencing stability. Targeting residues 21-33 in PSM-β1 and PSM-β2 offers a promising therapeutic approach for disrupting biofilm integrity. This study advances our understanding of PSM-β1 and PSM-β2 self-assembly and presents new targets for drug design against biofilm-associated diseases.

Bacterial biofilm-based bioleaching: Sustainable mitigation and potential management of e-waste pollution.

Significant advances in the electrical and electronic industries have increased the use of electrical and electronic equipment and its environmental emissions. The e-waste landfill disposal has deleterious consequences on human health and environmental sustainability, either directly or indirectly. E-waste containing ferrous and non-ferrous materials can harm the surrounding aquatic and terrestrial environments. Therefore, recycling e-waste and recovering metals from it before landfill disposal is an important part of environmental management. Although various chemical and physical processes are being used predominantly to recover metals from e-waste, the bioleaching process has gained popularity in recent years due to its eco-friendliness and cost-effectiveness. Direct contact between microbes and e-waste is crucial for continuous metal dissolution in the bio-leaching process. Biofilm formation is key for the continuous dissolution of metals from e-waste in contact bioleaching. Critical reviews on microbial activities and their interaction mechanisms on e-waste during metal bioleaching are scarce. Therefore, this review aims to explore the advantages and disadvantages of biofilm formation in contact bioleaching and the practical challenges in regulating them. In this review, sources of e-waste, available metallurgical methods, bioleaching process, and types of bioleaching microbes are summarized. In addition, the significance of biofilm formation in contact bioleaching and the role and correlation between EPS production, cyanide production, and quorum sensing in the biofilm are discussed for continuous metal dissolution. The review reveals that regulation of quorum sensing by exogenous and endogenous processes facilitates biofilm formation, leading to continuous metal dissolution in contact bioleaching.

Biofilm-based immobilized fermentation of engineered Komagataella phaffii for xylanase production

This study presented an immobilized fermentation process of engineered Komagataella phaffii with improved biofilm-forming abilities for continuous xylanase production and provided the first insights into the molecular basis of biofilm-based immobilized fermentation of K. phaffii. Overexpression of PAS_chr2-2_0178 and PAS_FragB_0067 in K. phaffii facilitated biofilm formation with 31.6% and 113.8% increasement, respectively. Subsequently, a biofilm-based immobilized fermentation process was developed for the PAS_FragB_0067-overexpressing strain. Xylanase production over five batches by GS115-0067* was better than that of GS115-xyn, with an overall average of 35.4 % higher enzyme activity. PAS_FragB_0067 overexpression resulted in better adhesion of K. phaffii cells on the carrier, and enhanced biofilms could provide more active cells in the immobilized fermentation process. Transcriptome analysis revealed that overexpression of the biofilm-related gene promoted central carbon metabolism. These findings offer a valuable reference strategy to improve production efficiency of K. phaffii cells in continuous fermentation processes.

Nanoimprinted Polymeric Structured Surfaces for Facilitating Biofilm Formation of Beneficial Bacteria

Initial studies indicate that structured polymer surfaces can support the attachment and biofilm formation of bacteria and thereby provide enhanced positive effects of beneficial bacteria, for instance in biocontrol in aquacultures. In this study, we demonstrate a test platform to further explore the surface topography for bacterial attachment and biofilm growth. It is based on a cyclic olefin copolymer (COC) materials platform, and nanoimprint technology was used for the replication of microstructures. The use of nanoimprint technology ensures precise micropattern transfer, enabling easy prototyping. Further, the process parameters of the mold preparation and nanoimprinting are discussed, with the purpose of optimizing the polymer pattern profile. This study has the potential to identify promising surfaces for biofilm growth of beneficial bacteria.

Exploring NRB Biofilm Adhesion and Biocorrosion in Oil/Water Recovery Operations Within Pipelines.

Microbially influenced corrosion represents a critical challenge to the integrity and durability of carbon steel infrastructure, particularly in environments conducive to biofilm formation by nitrate-reducing bacteria (NRB). This study investigated the impact of NRB biofilms on biocorrosion processes within oil/water recovery operations in Algerian pipelines. A comprehensive suite of experimental and analytical techniques, including microbial analysis, gravimetric methods, and surface characterization, were employed to elucidate the mechanisms of microbially influenced corrosion (MIC). Weight loss measurements revealed that carbon steel samples exposed to injection water exhibited a corrosion rate of 0.0125 mm/year, significantly higher than the 0.0042 mm/year observed in crude oil environments. The microbial analysis demonstrated that injection water harbored an average of (4.4 ± 0.56) × 106 cells/cm2 for sessile cells and (3.1 ± 0.25) × 105 CFU/mL for planktonic cells, in stark contrast to crude oil, which contained only (2.4 ± 0.34) × 103 cells/cm2 for sessile cells and (4.5 ± 0.12) × 102 CFU/mL for planktonic cells, thereby highlighting the predominant role of injection water in facilitating biofilm formation. Contact angle measurements of injection water on carbon showed 45° ± 2°, compared to 85° ± 4° for crude oil, suggesting an increased hydrophilicity associated with enhanced biofilm adhesion. Scanning electron microscopy further confirmed the presence of thick biofilm clusters and corrosion pits on carbon steel exposed to injection water, while minimal biofilm and corrosion were observed in the crude oil samples.

Inhibition of Oral Pathogenic Bacteria, Suppression of Bacterial Adhesion and Invasion on Human Squamous Carcinoma Cell Line (HSC-4 Cells), and Antioxidant Activity of Plant Extracts from Acanthaceae Family.

Medicinal plants have traditionally been used to treat various human diseases worldwide. In this study, we evaluated the leaf extracts of plants from the Acanthaceae family, specifically Clinacanthus nutans (Burm.f.) Lindau, Thunbergia laurifolia Lindl., and Acanthus ebracteatus Vahl., for their compounds and antioxidant activity. The ethanolic extracts of A. ebracteatus showed the highest total phenolic content at 22.55 mg GAE/g extract and the strongest antioxidant activities, with IC50 values of 0.24 mg/mL and 3.05 mg/mL, as determined by DPPH and ABTS assays. The antibacterial efficacy of these extracts was also tested against Streptococcus pyogenes, Streptococcus mutans, Staphylococcus aureus, and Klebsiella pneumoniae. The diameters of the inhibition zones ranged from 14.7 to 17.3 mm using the agar well diffusion method, with MIC and MBC values ranging from 7.81 to 250 mg/mL. Anti-biofilm formation, antibacterial adhesion, and antibacterial invasion assays further demonstrated that these medicinal plant extracts can inhibit bacterial biofilm formation and prevent the adhesion and invasion of oral pathogenic bacteria on the human tongue squamous cell carcinoma-derived cell line (HSC-4 cells). The ethanolic extracts of C. nutans and A. ebracteatus were able to inhibit the gtfD and gbp genes, which facilitate biofilm formation and bacterial adherence to surfaces. These findings provide new insights into the antibacterial and antioxidant properties of plant extracts from the Acanthaceae family. These activities could enhance the clinical and pharmaceutical applications of plant extracts as an alternative therapy for bacterial infections and a dietary supplement.

Medical Device-Associated Infections Caused by Biofilm-Forming Microbial Pathogens and Controlling Strategies.

Hospital-acquired infections, also known as nosocomial infections, include bloodstream infections, surgical site infections, skin and soft tissue infections, respiratory tract infections, and urinary tract infections. According to reports, Gram-positive and Gram-negative pathogenic bacteria account for up to 70% of nosocomial infections in intensive care unit (ICU) patients. Biofilm production is a main virulence mechanism and a distinguishing feature of bacterial pathogens. Most bacterial pathogens develop biofilms at the solid-liquid and air-liquid interfaces. An essential requirement for biofilm production is the presence of a conditioning film. A conditioning film provides the first surface on which bacteria can adhere and fosters the growth of biofilms by creating a favorable environment. The conditioning film improves microbial adherence by delivering chemical signals or generating microenvironments. Microorganisms use this coating as a nutrient source. The film gathers both inorganic and organic substances from its surroundings, or these substances are generated by microbes in the film. These nutrients boost the initial growth of the adhering bacteria and facilitate biofilm formation by acting as a food source. Coatings with combined antibacterial efficacy and antifouling properties provide further benefits by preventing dead cells and debris from adhering to the surfaces. In the present review, we address numerous pathogenic microbes that form biofilms on the surfaces of biomedical devices. In addition, we explore several efficient smart antiadhesive coatings on the surfaces of biomedical device-relevant materials that manage nosocomial infections caused by biofilm-forming microbial pathogens.

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.

Create artilysins from a recombinant library to serve as bactericidal and antibiofilm agents targeting Pseudomonas aeruginosa

Pseudomonas aeruginosa is a critical pathogen and novel treatments are urgently needed. The out membrane of P. aeruginosa facilitates biofilm formation and antibiotic resistance, and hinders the exogenous application against Gram-negative bacteria of endolysins. Engineered endolysins are investigated for enhancing antimicrobial activity, exemplified by artilysins. Nevertheless, existing research predominantly relies on laborious and time-consuming approaches of individually artilysin identification. This study proposes a novel strategy for expedited artilysin discovery using a recombinant artilysin library comprising proteins derived from 38 antimicrobial peptides and 8 endolysins. In this library, 19 colonies exhibited growth inhibition against P. aeruginosa exceeding 50 %, and three colonies were designated as dutarlysin-1, dutarlysin-2 and dutarlysin-3. Remarkably, dutarlysin-1, dutarlysin-2 and dutarlysin-3 demonstrated rapid and enhanced antibacterial activity, even minimum inhibitory concentration of them killed approximately 4.93 lg units, 6.75 lg units and 5.36 lg units P. aeruginosa, respectively. Dutarlysins were highly refractory to P. aeruginosa resistance development. Furthermore, 2 μmol/L dutarlysin-1 and dutarlysin-3 effectively eradicated over 76 % of the mature biofilm. These dutarlysins exhibited potential broad-spectrum activity against hospital susceptible Gram-negative bacteria. These results supported the effectiveness of this artilysins discovery strategy and suggested dutarlysin-1 and dutarlysin-3 could be promising antimicrobial agents for combating P. aeruginosa.

Ecological filter walls for efficient pollutant removal from urban surface water

Urban surface water pollution poses significant threats to aquatic ecosystems and human health. Conventional nitrogen removal technologies used in urban surface water exhibit drawbacks such as high consumption of carbon sources, high sludge production, and focus on dissolved oxygen (DO) concentration while neglecting the impact of DO gradients. Here, we show an ecological filter walls (EFW) that removes pollutants from urban surface water. We utilized a polymer-based three-dimensional matrix to enhance water permeability, and emergent plants were integrated into the EFW to facilitate biofilm formation. We observed that varying aeration intensities within the EFW's aerobic zone resulted in distinct DO gradients, with an optimal DO control at 3.19 ± 0.2 mg L−1 achieving superior nitrogen removal efficiencies. Specifically, the removal efficiencies of total organic carbon, total nitrogen, ammonia, and nitrate were 79.4%, 81.3%, 99.6%, and 79.1%, respectively. Microbial community analysis under a 3 mg L−1 DO condition revealed a shift in microbial composition and abundance, with genera such as Dechloromonas, Acinetobacter, unclassified_f__Comamonadaceae, SM1A02 and Pseudomonas playing pivotal roles in carbon and nitrogen elimination. Notably, the EFW facilitated shortcut nitrification-denitrification processes, predominantly contributing to nitrogen removal. Considering low manufacturing cost, flexible application, small artificial trace, and good pollutant removal ability, EFW has promising potential as an innovative approach to urban surface water treatment.

Characterization of Brevibacillus biofilm isolated from pasteurized milk and evaluation of the efficacy of sodium hypochlorite, CIP, and enzymatic treatment against the biofilm

Bacterial biofilms pose significant food safety threats to the dairy industry. This study identified Brevibacillus contamination in pasteurized milk at a processing plant, with biofilm formation observed on polyethylene plastic and stainless steel surfaces. The presence of milk promoted robust growth of Brevibacillus, facilitating biofilm formation and spore production. Biofilm structure, nanowires, and potential swelling were visualized on SEM images. Raman spectroscopy analysis revealed enrichment of lipids and amide I in milk-formed biofilms, resulting in a hydrophobic tendency as evidenced by contact angle measurements. Cultivable cell counts in milk-formed biofilms post-treatment with sodium hypochlorite or the alkaline and acid regime were approximately 7 and 3 log CFU/well, respectively. Effective biofilm removal was achieved through enzymatic treatment (lipase and DNase I) followed by an alkaline and acid regime. These findings underscore the pivotal role of biofilms in contaminating milk processing plants and highlight the urgent need for effective biofilm control strategies to safeguard the dairy industry.

SRNA molecules participate in hyperosmotic stress response regulation in Sphingomonas melonis TY.

Drought and salinity are ubiquitous environmental factors that pose hyperosmotic threats to microorganisms and impair their efficiency in performing environmental functions. However, bacteria have developed various responses and regulatory systems to cope with these abiotic challenges. Posttranscriptional regulation plays vital roles in regulating gene expression and cellular homeostasis, as hyperosmotic stress conditions can lead to the induction of specific small RNA molecules (sRNAs) that participate in stress response regulation. Here, we report a candidate functional sRNA landscape of Sphingomonas melonis TY under hyperosmotic stress, and 18 sRNAs were found with a clear response to hyperosmotic stress. These findings will help in the comprehensive analysis of sRNA regulation in Sphingomonas species. Weighted correlation network analysis revealed a 263 nucleotide sRNA, SNC251, which was transcribed from its own promoter and showed the most significant correlation with hyperosmotic response factors. Deletion of snc251 affected biofilm formation and multiple cellular processes, including ribosome-related pathways, aromatic compound degradation, and the nicotine degradation capacity of S. melonis TY, while overexpression of SNC251 facilitated biofilm formation by TY under hyperosmotic stress. Two genes involved in the TonB system were further verified to be activated by SNC251, which also indicated that SNC251 is a trans-acting sRNA. Briefly, this research reports a landscape of sRNAs participating in the hyperosmotic stress response in S. melonis and reveals a novel sRNA, SNC251, which contributes to the S. melonis TY biofilm formation and thus enhances its hyperosmotic stress response ability.IMPORTANCESphingomonas species play a vital role in plant defense and pollutant degradation and survive extensively under drought or salinity. Previous studies have focused on the transcriptional and translational responses of Sphingomonas under hyperosmotic stress, but the posttranscriptional regulation of small RNA molecules (sRNAs) is also crucial for quickly modulating cellular processes to adapt dynamically to osmotic environments. In addition, the current knowledge of sRNAs in Sphingomonas is extremely scarce. This research revealed a novel sRNA landscape of Sphingomonas melonis and will greatly enhance our understanding of sRNAs' acting mechanisms in the hyperosmotic stress response.

Nano zero-valent iron functioned 3D printing graphene aerogel electrode for efficient solar-driven biocatalytic methane production

To address the urgent need for developing carbon-neutral technologies, microbial electrosynthesis (MES), as an important contributor to the renewable energy field, can convert carbon dioxide to multi-carbon chemicals using microbes serving as living catalysts at the cathode. However, the performance of the cathode is restricted by the weak electrochemical reaction kinetics of the organisms, the specific area of the electrode, and the mass transfer under high current. Herein, we report a facile 3D-printed graphene aerogel (GA) electrode built with a nanozero-valent iron (NZVI)-functionalized graphene ink. The 3D-printed GA electrode was designed to possess hierarchical pores with an enhanced high specific surface area for microbial colonization while ensuring mass transfer. NZVI can assist in-situ hydrogen generation, facilitating biofilm formation and methane (CH4) production in the indirect electron transfer pathway. Consequently, the optimized 3D-printed electrode achieved a maximum CH4 production rate of 6993 ± 832 mmol/m2/d with a faradaic efficiency of 83.7%, which increased by 3.24-fold to the carbon felt electrode. In addition, integrating the proposed cathode into a PV-electrolyzer cell yielded a solar-to-CH4 efficiency of 4.70%. This study provides a unique method for the development of advanced cathodes and underscores the potential of integrating MES with renewable energy technologies.

Impact of polymeric films and hydrogels: Physical characteristics on bacterial growth

AbstractHydrogels find diverse applications in manipulating bacteria, and serving purposes like elevation, maintenance, and elimination. Several factors of hydrogel have been studied in the benefits of antibacterial activity. Factors such as hydrogel stiffness and roughness gain significance in surface coating, influencing bacterial behavior. However, the intricate interplay of hydrogel stiffness, roughness, polymer types, and bacterial species necessitates further exploration. The choice of polymer is dictated by the specific objectives, particularly in antibacterial scenarios where polymers with positive charge, hydrophilicity, and acidity prove effective. These properties induce robust electrostatic and hydrophobic/hydrophilic interactions, along with pH‐induced cell membrane damage, collectively contributing to hindered bacterial adhesion and growth. Additionally, extracellular polymeric substances (EPS) emerge as pivotal influencers in bacterial adhesion and proliferation. EPS production alters bacterial surfaces, fostering connections between bacteria and facilitating biofilm formation. The hydrophobic nature of EPS further complicates bacterial interactions with surface materials, emphasizing the nuanced interplay of hydrophilic and hydrophobic forces in bacterial adhesion. Herein, this work article has reviewed the related study of each physical property related to antibacterial property on the surface of the hydrogel. Moreover, this work also illustrates applications of the antibacterial properties of hydrogel for medical and surface treatment, including wound healing, food packaging, and surface coating. Additionally, the bacteria growing on hydrogel for engineered living materials, have been updated in various applications.

Efficacy and Experience of Bacteriophages in Biofilm-Related Infections.

Bacterial infection has always accompanied human beings, causing suffering and death while also contributing to the advancement of medical science. However, the treatment of infections has become more complex in recent times. The increasing resistance of bacterial strains to antibiotics has diminished the effectiveness of the therapeutic arsenal, making it less likely to find the appropriate empiric antibiotic option. Additionally, the development and persistence of bacterial biofilms have become more prevalent, attributed to the greater use of invasive devices that facilitate biofilm formation and the enhanced survival of chronic infection models where biofilm plays a crucial role. Bacteria within biofilms are less susceptible to antibiotics due to physical, chemical, and genetic factors. Bacteriophages, as biological weapons, can overcome both antimicrobial resistance and biofilm protection. In this review, we will analyze the scientific progress achieved in vitro to justify their clinical application. In the absence of scientific evidence, we will compile publications of clinical cases where phages have been used to treat infections related to biofilm. The scientific basis obtained in vitro and the success rate and safety observed in clinical practice should motivate the medical community to conduct clinical trials establishing a protocol for the proper use of bacteriophages.

Motility behavior and physiological response mechanisms of aerobic denitrifier, Enterobacter cloacae strain HNR under high salt stress: Insights from individual cells to populations

The motility behaviors at the individual-cell level and the collective physiological responsive behaviors of aerobic denitrifier, Enterobacter cloacae strain HNR under high salt stress were investigated. The results revealed that as salinity increased, electron transport activity and adenosine triphosphate content decreased from 15.75 μg O2/g/min and 593.51 mM/L to 3.27 μg O2/g/min and 5.34 mM/L, respectively, at 40 g/L, leading to a reduction in the rotation velocity and vibration amplitude of strain HNR. High salinity stress (40 g/L) down-regulated genes involved in ABC transporters (amino acids, sugars, metal ions, and inorganic ions) and activated the biofilm-related motility regulation mechanism in strain HNR, resulting in a further decrease in flagellar motility capacity and an increase in extracellular polymeric substances secretion (4.08 mg/g cell of PS and 40.03 mg/g cell of PN at 40 g/L). These responses facilitated biofilm formation and proved effective in countering elevated salt stress in strain HNR. Moreover, the genetic diversity associated with biofilm-related motility regulation in strain HNR enhanced the adaptability and stability of the strain HNR populations to salinity stress. This study enables a deeper understanding of the response mechanism of aerobic denitrifiers to high salt stress.

Synergistic effect of LDHs/loofah composites for in-situ remediation of nitrate in contaminated groundwater

Permeable reaction barrier (PRB) is an innovative technology for in-situ remediation of nitrate-contaminated groundwater. In this study, layered double hydroxides (LDHs)/loofah composites were prepared and used as active fillers for PRB to facilitate nitrate removal from groundwater. Under the conditions of initial nitrate concentration of 5 mg/L, a hydraulic retention time (HRT) of 4 h, and without additional carbon source, the nitrate removal rates of the natural loofah, MgAl-LDHs, and CaMgAl-LDHs composite were 69.31 %, 85.35 %, and 97.82 %, respectively. The CaMgAl-LDHs composite exhibits the highest denitrification capacity, attributed to the presence of Ca2+and Mg2+. Ca2+ and Mg2+is an essential element for the structural integrity of microbial cells, which demonstrated that Ca2+ reduces the surface charge of bacteria, leading to hydrophobicity and facilitating biofilm formation. Electrochemical tests demonstrate that LDHs with distinctive two-dimensional layered structure, contribute to the augmentation of electron transfer during denitrification. LDHs can also promote the formation of highly active biofilms and the secretion of extracellular polymeric substances (EPS) on the surface of loofah, thereby enhancing the metabolic activity of microorganisms. Metagenomic analysis revealed that LDHs enhance the enrichment of denitrifying bacteria and the activity of key enzymes involved in denitrification. Therefore, the adsorption-biological coupled degradation of the LDHs/loofah composites have great potential to enhance the efficiency of biological denitrification, making it promising filling materials for PRB technology applied in groundwater remediation.

Self-assembled hierarchical porous carbon nanotube sponge bioanode for energy harvesting and gaseous toluene removal

Microbial fuel cells (MFCs) have emerged as a promising technology with potential for volatile organic compounds (VOCs) treatment and energy recovery. However, the low efficiency of electron transfer between microorganisms and electrodes has limited their degradation ability and power output. To address this issue, we designed a macroscopic hierarchical porous super-aligned carbon nanotube (SACNT) sponge bioanode. The hierarchical structure of the SACNT anode exhibited an appropriate distribution of macro/mesopores. The large pores facilitated biofilm formation and mass transfer, enhancing direct electron transfer between bacteria and SACNTs. The abundant mesopores augmented adsorption and electrochemical reaction sites, thereby enhancing flavin-mediated indirect electron transfer. This hierarchical pore structure induced the formation of biofilms mainly composed of electroactive bacteria and toluene-degrading bacteria, promoting toluene removal and power generation. The MFC demonstrated an exceptional power density of 726.18 mW m−2, surpassing existing toluene-fueled MFCs, while achieving the toluene elimination capacity of 61.29 g m−3 h−1.

Molecular Adhesion of a Pilus-Derived Peptide Involved in Pseudomonas aeruginosa Biofilm Formation on Non-Polar ZnO-Surfaces.

Bacterial colonization and biofilm formation on abiotic surfaces are initiated by the adhesion of peptides and proteins. Understanding the adhesion of such peptides and proteins at a molecular level thus represents an important step toward controlling and suppressing biofilm formation on technological and medical materials. This study investigates the molecular adhesion of a pilus-derived peptide that facilitates biofilm formation of Pseudomonas aeruginosa, a multidrug-resistant opportunistic pathogen frequently encountered in healthcare settings. Single-molecule force spectroscopy (SMFS) was performed on chemically etched ZnO surfaces to gather insights about peptide adsorption force and its kinetics. Metal-free click chemistry for the fabrication of peptide-terminated SMFS cantilevers was performed on amine-terminated gold cantilevers and verified by X-ray photoelectron spectroscopy (XPS) and polarization-modulated infrared reflection absorption spectroscopy (PM-IRRAS). Atomic force microscopy (AFM) and XPS analyses reveal stable topographies and surface chemistries of the substrates that are not affected by SMFS. Rupture events described by the worm-like chain model (WLC) up to 600 pN were detected for the non-polar ZnO surfaces. The dissociation barrier energy at zero force ΔG(0), the transition state distance xb and bound-unbound dissociation rate at zero force koff (0) for the single crystalline substrate indicate that coordination and hydrogen bonds dominate the peptide/surface interaction.