Biofilm Growth Research Articles

Engineering and Clinical Study of Surface Geometry of Clear Aligners at the Nanoscale

This paper investigates the evolution of the outer surface geometry of Invisalign®—clear orthodontic aligners—caused by degradation triggered by wearing. The obtained results served to confirm whether or not the aligners could continue to be used once their wear time in the therapeutic procedure had ended, taking both their geometric and mechanical features into account. The measurements were performed using atomic force microscopy which allowed the mapping of nanomechanical properties. The obtained images were then processed to determine statistical and functional surface geometry parameters in accordance with relevant ISO standards. The results revealed that the unrepeatability of the manufacturing process causes the surface shape parameters of new aligners to be irregular; however, these features become gradually consistent for worn samples. On the other hand, properly used aligners may change in two ways: the outer layer flattens and its thickness decreases, and at the same time the Young’s modulus of the material decreases. It follows that the degradation processes may be caused by tribological phenomena (abrasion of contact surfaces) and/or biochemical phenomena (biofilm growth, decomposition of the material under the influence of enzymes in the oral cavity).

Microbial growth within porous gravity currents

The effect of microbial activity on buoyancy-driven flow within a porous layer is analysed. The input fluid provides an energy source for the growth of biofilms on the porous rock. At each location within the porous layer, the porosity and permeability begin to decrease once the input fluid has invaded. This leads to an evolving rock heterogeneity that depends on the passing time of the input fluid. Hence, the evolution of the flow is partly controlled by its own history. We present an axisymmetric gravity current model, accounting for this effect. In general, a reduction in permeability leads to the flow having a lesser extent in the radial direction and greater thickness (extent in the cross-flow direction), whilst a reduction in porosity has negligible effect on the thickness but leads to a much greater radial extent. The flow is fastest near the free surface where the permeability is greatest. In the case where the porosity and permeability reduce as power-law functions of fluid residence time, the evolution of the flow and the rock properties are self-similar. Consumption of the input fluid by the microbes is also incorporated in the model and it generally leads to flows with lesser radial extent but little change in the thickness. The three impacts of microbial growth (volume loss owing to consumption and the reduction in permeability and porosity) each influence the flow in substantially different ways and the interplay is analysed. A motivation of the study, the underground storage of hydrogen, is briefly discussed.

Bacterial single-cell RNA sequencing captures biofilm transcriptional heterogeneity and differential responses to immune pressure

Biofilm formation is an important mechanism of survival and persistence for many bacterial pathogens. These multicellular communities contain subpopulations of cells that display metabolic and transcriptional diversity along with recalcitrance to antibiotics and host immune defenses. Here, we present an optimized bacterial single-cell RNA sequencing method, BaSSSh-seq, to study Staphylococcus aureus diversity during biofilm growth and transcriptional adaptations following immune cell exposure. BaSSSh-seq captures extensive transcriptional heterogeneity during biofilm compared to planktonic growth. We quantify and visualize transcriptional regulatory networks across heterogeneous biofilm subpopulations and identify gene sets that are associated with a trajectory from planktonic to biofilm growth. BaSSSh-seq also detects alterations in biofilm metabolism, stress response, and virulence induced by distinct immune cell populations. This work facilitates the exploration of biofilm dynamics at single-cell resolution, unlocking the potential for identifying biofilm adaptations to environmental signals and immune pressure.

Acoustic Fingerprinting and Nanoslip Dynamics of Biofilms

AbstractIt is reported that bacteria can generate nanomotion, but understanding the complex dynamics of bacterial colony gliding on solid interfaces has remained unresolved. Here, this work captures the real‐time development and gliding of bacterial biofilms on vibrating solids made of piezoelectric quartz. The gliding, characterized by liquid slips, is measured in form of frequency and dissipation changes of the vibrating solid. These vibrations enable the generation of distinct acoustic fingerprints (sound/ music) of the three phases of biofilm development: viscoelastic strengthening, biofilm growth and biofilm stability. In adition, the effect of extracellular matrix secretion on the rigidity of the film and its nanoslip in each of the distinct biofilm developmental phases is quantified. This work provides a real‐time, label‐free method of quantifying bacteria biofilm dynamics and paves the way for developing libraries of acoustic signatures of bacteria and their metabolic products.

Optically accessible, 3D-printed flow chamber with integrated sensors for the monitoring of oral multispecies biofilm growth in vitro.

The formation of pathogenic multispecies biofilms in the human oral cavity can lead to implant-associated infections, which may ultimately result in implant failure. These infections are neither easily detected nor readily treated. Due to high complexity of oral biofilms, detailed mechanisms of the bacterial dysbiotic shift are not yet even fully understood. In order to study oral biofilms in more detail and develop prevention strategies to fight implant-associated infections, in vitro biofilm models are sorely needed. In this study, we adapted an in vitro biofilm flow chamber model to include miniaturized transparent 3D-printed flow chambers with integrated optical pH sensors - thereby enabling the microscopic evaluation of biofilm growth as well as the monitoring of acidification in close proximity. Two different 3D printing materials were initially characterized with respect to their biocompatibility and surface topography. The functionality of the optically accessible miniaturized flow chambers was then tested using five-species biofilms (featuring the species Streptococcus oralis, Veillonella dispar, Actinomyces naeslundii, Fusobacterium nucleatum, and Porphyromonas gingivalis) and compared to biofilm growth on titanium specimens in the established flow chamber model. As confirmed by live/dead staining and fluorescence in situ hybridization via confocal laser scanning microscopy, the flow chamber setup proved to be suitable for growing reproducible oral biofilms under flow conditions while continuously monitoring biofilm pH. Therefore, the system is suitable for future research use with respect to biofilm dysbiosis and also has great potential for further parallelization and adaptation to achieve higher throughput as well as include additional optical sensors or sample materials.

Integrating Biofilm Growth and Degradation into a Model of Microplastic Transport in the Arctic Ocean

Integrating Biofilm Growth and Degradation into a Model of Microplastic Transport in the Arctic Ocean

“On-demand” nanosystem-integrated microneedles for amplified triple therapy against recalcitrant bacteria and biofilm growth

Phototherapy has emerged to eradicate recalcitrant bacteria without causing drug resistance, but it is often accompanied by considerable limitations owing to a high tolerance of recalcitrant bacteria to heat and oxidative damage, leading to low efficiency of monotherapy and unwanted side effects. Assuming that employing antimicrobial peptides (AMPs) to disrupt bacterial membranes could reduce bacterial tolerance, a multifunctional “on-demand” nanosystem based on zeolitic imidazolate framework-8 (ZIF-8) with metal ions for intrinsic antibacterial activity was constructed to potently kill methicillin-resistant Staphylococcus aureus (MRSA). Then, microneedles (MNs) were used to transdermally deliver the ZIF-8-based nanosystem for localized skin infection. After MNs insertion, the nanoplatform could specifically deliver the loaded therapeutic components to bacterial infection sites through employing hyaluronic acid (HA) as a capping agent, thus realizing the “on-demand” payload release triggered by excess hyaluronidase secreted by MRSA. The prepared nanosystem and MNs were confirmed to exert an amplified triple therapy originating from membranolytic effect, phototherapy, and ion therapy, thus displaying a powerful bactericidal and MRSA biofilm destruction ability. This intelligent antimicrobial strategy may bring a dawn of hope for eradicating multidrug-resistant bacteria and biofilms.

Different management strategies for artificial substrates on nitrification, microbial composition, and growth of Penaeus vannamei in a super-intensive biofloc system

The aim of this study was to test the effect of different management strategies for artificial substrates on the nitrification process, microbial composition of water and biofilm, and growth of Penaeus vannamei in a super-intensive biofloc system. The research was conducted over 60 days using experimental units of 200 L and had the following treatments: T1 – artificial substrate + biofloc + shrimp + aeration (control), T2 - artificial substrate + water + aeration, T3 - artificial substrate + water, and T4 - only artificial substrate. The experiment was divided into two phases. Phase 1 involved maintaining the artificial substrates under the management strategy for 30 days. Phase 2 involved the use of substrates from phase 1 in a shrimp nursery for 30 days. Pre colonized artificial substrates (Needlona®) were employed at a ratio of 200 % of the tank's lateral area to promote biofilm growth. In the phase 1, T1 used a stocking density of 500 shrimp m−3 (9.72 ± 0.50 g). In phase 2, shrimp weighing 0.10 ± 0.05 g were stocked at a density of 1750 shrimp m−3 and all treatments included artificial substrates from phase 1, aeration, water, and shrimp. Molasses was the carbon source organic used. In phase 2, ammonia control was observed in treatments T2, T3, and T4 from the 10th day onwards. T4 had a nitrite spike, controlled from day 14 onwards, suggesting recovery of the nitrifying bacteria community. At the end of the phase 2, T2 and T4 showed higher abundance of coccoid bacteria in the biofilm compared to T1 and T3. T4 also had more bacillus. The shrimp final weight was higher in T2 compared to the other treatments. These findings suggest that maintaining the substrate submerged in water (T3) can be considered a practical management for artificial substrates and that it does not limit the nitrification process between culture cycles. Furthermore, exposure of artificial substrates to air (T4) also did not affect the nitrification process, leading to the recovery of the bacterial community, and the proliferation of various bacterial groups.

Environmental pH and compound structure affect the activity of short-chain carboxylic acids against planktonic growth, biofilm formation, and eradication of the food pathogen Salmonella enterica.

Short-chain carboxylic acids (SCCAs) that are naturally produced by microbial fermentation play an essential role in delaying microbial spoilage. SCCAs are structurally diverse, but only a few of them are routinely used in food biopreservation. This study investigated the effects of environmental pH and intrinsic properties of 21 structurally different SCCAs on the antimicrobial and antibiofilm activity against Salmonella enterica. Inhibition of SCCA toward planktonic and biofilm growth of S. enterica was higher in an acidic environment (pH 4.5) that is common in fermented products, and for SCCA that possessed both a high acid dissociation strength (pKa) (>4.0) and a positive hydrophobicity [octanol/water partition coefficient (log Kow)]. Crotonic and caproic acids were identified as SCCAs with potential as biopreservatives even at near-neutral pH. SCCA with hydrophilic groups such as lactic acid did not inhibit S. enterica at concentrations up to 50 mM, while SCCA with benzene or methyl groups or a double bond prevented S. enterica growth and biofilm formation. Stimulation of biofilm formation was observed for formic, acetic, and propionic acid close to the minimum inhibitory concentration to reduce 50% of cell density (MIC50) of planktonic cells, and for citric and isocitric acid with an MIC50 of ≥50 mM. The presence of low concentrations of formic and propionic acids during biofilm formation conferred protection during eradication possibly due to a pre-adaptation effect, yet two consecutive acid treatments were successful in eradicating biofilms if the first acid treatment was two- to threefold of the MIC50.IMPORTANCEThis study provides a systematic comparison on the antimicrobial and antibiofilm activity of more than 20 structurally different SCCAs against a common food pathogen. We tested the antimicrobial activity at controlled pH and identified the structure-dependent antimicrobial effects of SCCA without the confounding influence of acidification. The combined effect of pKa and log Kow was identified as an important feature that should be considered when deciding for a specific SCCA in the application as antimicrobial. Our results imply that additional phenomena such as the use of SCCA as substrate and cellular pre-adaption effects have to be taken into consideration. We finally present a two-step treatment as an efficient approach to eradicate biofilms, which can be applied for the disinfection of contact surfaces and manufacturing equipment. Results obtained here can serve as guidelines for application of SCCA to avoid the growth of food pathogens and/or to develop biopreserved food systems.

Biofilm Growth in Porous Media Well Approximated by Fractal Multirate Mass Transfer With Advective‐Diffusive Solute Exchange

AbstractBiofilm growth in porous media changes not only the hydrodynamic properties of the medium (reduction in porosity and permeability, and increase in dispersivity), but also the transport itself (breakthrough curves display increasingly fast first arrivals and long tails). These features are well reproduced by multicontinuum models (Multi‐Rate Mass Transfer, MRMT) which can be used to describe reactive transport in heterogeneous porous media and facilitate the simulation of reactions that are localized within biofilms. Here, we present a conceptual and numerical model of biochemical reactive transport with dynamic biofilm growth based on MRMT formulations. Mass exchange between mobile water and immobile biofilm aggregates is represented by a memory function, which simplifies definition of MRMT parameters. We successfully tested this model on two sets of laboratory data and found that (a) a basic model based on the growth of uniformly sized biofilm aggregates fails to reproduce laboratory tracer tests and rate of biofilm growth, while a fractal growth model, which we obtain by integrating the memory functions of biofilm aggregates with a power law distribution, does; (b) the biofilm memory function evolves as the biofilm grows; and (c) the early time portion of eluted volume tracer breakthrough curves are independent of flow rate, whereas the tail becomes heavier when the flow rate is decreased, which implies that both advection controlled and diffusion controlled mass exchange coexist in biofilms. These findings imply that porous media biofilms are essentially different from those developing in human tissues or open spaces.

Light Intensity Effects on Bioproduct Recovery from Fuel Wastewater Using Purple Phototrophic Bacteria in a Hybrid Biofilm-Suspended Growth System.

This research looked at how three different light intensities (1600, 4300, and 7200 lx) affect the biomass development, treatment of fuel synthesis wastewater and the recovery of valuable bioproducts between biofilm and suspended growth in a purple-bacteria enriched photobioreactor. Each condition was run in duplicate using an agricultural shade cloth as the biofilm support media in a continuously mixed batch reactor. The results showed that the highest chemical oxygen demand (COD) removal rate (56.8 ± 0.9%) was found under the highest light intensity (7200 lx), which also led to the most biofilm formation and highest biofilm biomass production (1225 ± 95.7 mg). The maximum carotenoids (Crts) and bacteriochlorophylls (BChls) content occurred in the suspended growth of the 7200 lx reactor. BChls decreased with light intensity in suspended growth, while in biofilm both Crts and BChls were relatively stable between light conditions, likely due to an averaging effect as biofilm thickened at higher light intensity. Light intensity did not affect protein content of the biomass, however, biofilm showed a lower average (41.2% to 43.7%) than suspended biomass (45.4% to 47.7%). For polyhydroxybutyrate (PHB) the highest cell concentration in biofilm occurred at 1600 lx (11.4 ± 2.4%), while for suspended growth it occurred at 7200 lx (22.7 ± 0.3%), though total PHB productivity remained similar between reactors. Shading effects from the externally located biofilm could explain most variations in bioproduct distribution. Overall, these findings suggest that controlling light intensity can effectively influence the treatment of fuel synthesis wastewater and the recovery of valuable bioproducts in a biofilm photobioreactor.

Light-responsive zwitterionic membrane surface modification for antifouling and antibacterial application

Light-responsive surface modifications offer a promising solution for reducing membrane fouling by enabling remote, contactless cleaning without altering the chemical environment. While traditional methods make membranes hydrophilic to resist fouling, biofouling remains difficult to remove and often requires harsh bactericidal treatments. With the rise of antimicrobial resistance (AMR), there is a pressing need for alternative, non-bactericidal strategies to control biofilm growth. In this study, we developed an efficient approach by coating commercial ultrafiltration polyethersulfone (PES) membranes with a copolymer of light-responsive azobenzene (AZO) and zwitterionic sulfobetaine methacrylate (SBMA). The photochemical conversion efficiency and photokinetic parameters of the copolymer, due to light-induced trans–cis-trans conversion, were systematically determined. During filtration, the modified membranes showed excellent resistance to reversible fouling with bovine serum albumin (BSA). The fouled membrane became reusable after near-complete removal of irreversible fouling, including bacteria (Pseudomonas aeruginosa), by activating the AZO units with UV–vis light, providing an effective strategy for fouling control.

Tooth-Binding Graphene Quantum Dots Silver Nanocomposites for Prevention of Dental Caries.

The objectives of this study were to develop a tooth-binding graphene quantum dots silver nanocomposites (ALN-GQDs-Ag) and evaluate their antibacterial, mineralising, and discolouring properties for the prevention of dental caries. In this study, ALN-GQDs-Ag were developed by synthesising nano silver (Ag) with graphene quantum dots (GQDs) and functionalised GQDs with alendronate (ALN). ALN-GQDs-Ag were characterised by transmission electron microscopy (TEM), zeta potential analysis, X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), and Raman spectroscopy. The cytotoxicity of ALN-GQDs-Ag against human gingival fibroblasts (HGF-1) and stem cells from human exfoliated deciduous teeth (SHED) was examined using a colorimetric assay with reference to silver nitrate solution. The affinity of ALN-GQDs-Ag for hydroxyapatite particles was investigated using inductively coupled plasma spectroscopy (ICP). The antibacterial properties of ALN-GQDs-Ag against Streptococcus mutans were evaluated by scanning electron microscopy (SEM), confocal laser scanning microscopy (CLSM), and colony-forming units counting (CFUs). The mineralisation properties of ALN-GQDs-Ag on human dentine were assessed using micro-computed tomography (micro-CT), scanning electron microscopy (SEM), and Fourier transform infrared in a biochemical cycling model. The discolouring properties of ALN-GQDs-Ag on artificial dentine caries were determined using spectrophotometry. TEM, Zeta potential, XPS, FTIR, and Raman spectroscopy confirmed the synthesis of stable spherical ALN-GQD-Ag nanocomposites with a 10.3 ± 5.5 nm diameter. The colorimetric assay demonstrated that ALN-GQDs-Ag were less cytotoxic than silver nitrate to HGF-1 and SHED (p<0.001). ICP showed that ALN-GQDs-Ag were bound to hydroxyapatite. SEM, CLSM, and CFUs showed that ALN-GQDs-Ag was bactericidal and inhibited biofilm growth of Streptococcus mutans. Micro-CT, SEM, and FTIR showed that ALN-GQDs-Ag repressed dentine demineralisation under a cariogenic challenge. Spectrophotometry revealed no significant discolouration of dentine caries in the ALN-GQDs-Ag. This study developed a biocompatible and tooth-binding ALN-GQDs-Ag with promising antibacterial, mineralising, and non-discolouring properties. ALN-GQDs-Ag could be a novel anti-caries agent for preventing dentine caries if translated for clinical use.

Biofilm growth Dynamics in a Micro-Irrigation with Reclaimed Wastewater in the Field scale.

The dripper clogging due to the development of biofilm can reduce the benefits of micro-irrigation technology implementation using reclaimed wastewater. The narrow cross-section and labyrinth geometry of the dripper channel enhance the fouling mechanisms. The aim of this study was to evaluate the water distribution and biofouling of drip irrigation systems at the field scale during irrigation with treated wastewater. Six 100 m lines of commercial pipes with two pressure-compensating dripper types (flow rate, Q, of 0.65 L.h-1 and 1.5 L.h-1, respectively) were monitored for four months. Different zones along the pipes were selected to evaluate the influence of hydrodynamical conditions (Reynolds number = 5400 to 0) on biofouling. Destructive methods involving the biofilm extraction by mechanical means, showed little biofilm development without significant differences in dry and organic matter content in function of the sampling location along the pipe or dripper flow rate (Q0.65 and Q1.5). These results were confirmed by non-destructive methods, such as optical coherence tomography, that nevertheless showed that biofouling concerned 15-20% of the total dripper labyrinth volume. Total organic carbon monitoring and its composition (by three-dimensional excitation and emission matrix fluorescence microscopy) showed that the biofilm did not significantly influence the organic matter nature. Our results indicated that the biological activity and biofilm development in irrigation systems were more affected by the environmental conditions, particularly water temperature, rather than flow conditions. This confirmed that treated wastewater with low organic content can be used in micro-irrigation systems without significant loss of efficiency, even in conditions requiring intensive irrigation, such as the Mediterranean climate.

The effect of soaking heat-polymerized acrylic resin denture base in avocado seed extract (Persea americana Mill.) on the inhibition of denture-plaque microorganisms biofilm growth

Background Heat polymerized acrylic (HPA) resins are known to have high porosity that contributes to increased surface roughness and microcrack formation in stress areas. This facilitates the attachment and growth of polymicrobial biofilms contributing to increased antimicrobial resistance. Many research had been carried out on avocado seeds, but no research that studies avocado seeds effect on denture-plaque microorganism biofilm on HPA resin has been found. Methods This study used 144 samples (n=144), namely HPA resin discs covered with mono-species and polymicrobial biofilms. The discs were soaked for 8 hours in the 5%, 10%, 15%, 20% avocado seed extract, positive control (alkaline peroxide), and negative control (aquadest). Each disc was shaken with a vortex mixer for 1 minute, and 100 μL was added into 96-well microplates with three times repetition and incubated for 24 hours. A microtiter plate biofilm formation assay was then conducted The inhibition values were determined from the percentage inhibition value formula which required absorption values from a microplate reader (595 nm). The research data were analyzed using a univariant test, and a one-way ANOVA test, accompanied by Welch ANOVA on non-homogenous data. Results In this research, it was found that the MBIC50 of avocado seed extract against the mono-species of C. albicans (5%), C. glabrata (5%), A. odontolyticus (15%), S. gordonii (15%), S. aureus (10%), while against polymicrobial was 20%. There was a significant effect of soaking HPA resin in avocado seed extract on the inhibition of mono-species and polymicrobial biofilms with a value of p&lt;0.001 (p&lt;0.05). Conclusion The MBIC50 of avocado seed extract in polymicrobial biofilm group was higher than that in the mono-species biofilm groups. Although alkaline peroxide showed higher inhibition value than that of the MBIC50 in polymicrobial biofilm group, 20% avocado seed extract was concluded effective as it inhibited &gt;50% polymicrobial biofilm.

Comparative study on the virulence of mycobacteriophages.

The global tuberculosis (TB) epidemic affected 10 million people and caused 1.3 million deaths in 2022 alone. Multidrug-resistant TB is successfully treated in less than 60% of cases by long, expensive and aggressive treatments. Mycobacteriophages, viruses that can infect bacteria such as Mycobacterium tuberculosis-the species responsible for TB, have the potential to redefine TB prevention and treatments. However, the development of phage-based products necessitates the assessment of numerous parameters, including virulence and adsorption, to ensure their performance and quality. In this work, we characterized the virulence of three different mycobacteriophages (Fionnbharth, Muddy and D29), alone and as cocktails, against a TB model host (Mycobacterium smegmatis) under planktonic and early-stage biofilm growth conditions. Phage D29 and cocktails containing D29 had the highest virulence under all conditions. Interestingly, phages Fionnbharth and Muddy and their combination showed higher virulence against early-stage biofilm than against the planktonic phenotype. Adsorption assays indicated that all three phages had lower adsorption efficiencies on the early-stage biofilm phenotype than on the planktonic one, suggesting a reduced availability of receptors in the former. Given that, despite these lower adsorption efficiencies, the virulence of the phages and phage cocktails was either unchanged or higher against the early-stage biofilm, this phenotype must display properties that are favorable to other steps of the infection process. These results inform us on the dynamics of mycobacteriophage infections, alone and in cocktail formulations, under different host growth conditions, and serve as a basis for the development of phage products targeting mycobacteria biofilms.

Impact of carbon sources in airport de-icing compounds on the growth of Sphaerotilus natans.

Airport de-icing has been linked with the growth of undesirable river biofilms (URBs, formerly "sewage fungus"), a manifestation of organic pollution causing long-term ecological damage to watercourses. URBs are a polymicrobial community, with one key taxon standing out in literature: Sphaerotilus natans, a filamentous bacterium also found in sewage treatment and activated sludges. An industry often implicated in causing URBs is airport de-icing, with large biofilms often developing downstream of airport discharges in winter months. However, it is not yet clear which de-icers may cause URBs and how they influence growth. Therefore, specific objectives were to (i) determine which freeze-point depressants (FPDs) can be utilized by S. natans; (ii) examine differences in the growth kinetics between FPDs; and (iii) compare pure-FPDs to commercial airport de-icers (CADs) as carbon sources, to determine impacts of additives. This study employed a turbidimetric micro-batch culture design to conduct microbial growth experiments, using S. natans and a minimal medium supplemented with airport de-icer as the carbon source. Equimolar carbon concentrations were used to compare the effects of common FPDs and CADs - each containing a specific FPD. Growth was assessed via optical density (OD600) measurements, from which time-to-detection, maximum rate of change, and maximum optical density were derived and kinetics inferred. S. natans was found to grow effectively on all FPDs tested, although the microbial yield was heavily dependent on the carbon concentration for all FPDs and CADs. Sodium acetate generated the quickest growth, with the lowest TTD (lag-time) for all but the lowest concentrations tested. Propylene glycol produced the greatest maxOD (total growth), whereas ethylene glycol had a higher limiting concentration for maxROC (growth rate). The mixture of compounds and additives in commercial products did not significantly impact the growth of S. natans. This research provides evidence from controlled laboratory experiments that airport de-icers support the growth of S. natans. The differences in growth kinetics observed for the FPDs and CADs could inform improved mitigation or treatment to reduce the incidence and ecological impacts of URBs.

Enhancing the volatile organic compound and biomass production by three biocontrol potential bacteria in corn steep liquor growth medium and development of cell freeze-drying process.

This study investigates the traits of three plant growth-promoting (PGP) and antagonistic bacteria, Pseudomonas protegens MP12, Bacillus sp. 3R4, and Bacillus sp. T22, to assess their potential application as biocontrol agents by using the ecofriendly and low-cost substrate Corn Steep Liquor (CSL) medium. Analyses of antagonism through volatile organic compounds (VOCs) production, biofilm formation, and growth performance were carried out. Dual antagonism assay showed that all strains displayed significant antagonistic activity against Botrytis cinerea through VOCs. Gas chromatography demonstrated that strains in the CSL exhibited higher VOCs production than nutrient medium. Moreover, enhanced biofilm formation analysed by Calgary Biofilm Device, growth, and biomass were noted in CSL cultures. Pseudomonas protegens MP12, which showed higher cell concentration and biomass yield, was selected for freeze-drying treatments. Storage cell viability assays evidenced that it can be effectively preserved for nearly 7 months at 4°C. The results here obtained showed that CLS medium enhanced VOCs production, biofilm formation, growth, and biomass of the antagonistic bacteria of the three strains. Eventually, the more effective strain P. protegens MP12 can be stored for nearly 7 months at 4°C.

Biofilm formation dynamics in long-distance water conveyance pipelines: Impacts of nutrient levels and metal stress

Biofilm formation in long-distance water conveyance pipelines poses significant risks to water quality, particularly under varying nutrient levels and heavy metal stress. However, the impacts of pipeline material on biofilm formation dynamics under different raw water conditions remain elusive. This study investigated the effects of nutrient availability and Fe-Mn stress on biofilm development, structural stability, bacterial community composition, and the occurrence of viable but non-culturable (VBNC) bacteria. Using reactors with different nutrient conditions, we observed that increased nutrient levels promote biofilm growth but lead to greater instability, heightening the risk of secondary contamination. Notably, nutrient escalation beyond a critical threshold had a diminishing impact on biofilm community composition. Additionally, Fe-Mn stress, while initially enhancing microbial adhesion and metabolic activity, ultimately inhibited biofilm formation over time and increases the prevalence of VBNC bacteria, particularly on stainless steel (SS) surfaces. Our findings also highlighted the importance of material selection for pipelines, with polyvinyl chloride (PVC) showing reduced biofilm formation compared to SS, making it a more suitable option for transporting raw water in environments with high metal content. Dispersal limitation determined the bacterial community assembly during the biofilm formation, accounting for 64.53–90.67 % of the variability in different scenarios. These insights offer valuable guidance for managing biofilm-related issues in water distribution systems, emphasizing the need for careful control of nutrient levels and material choice to ensure water safety over long distances.

Bacterial Binding to Polydopamine-Coated Magnetic Nanoparticles.

In medical infections such as blood sepsis and in food quality control, fast and accurate bacteria analysis is required. Using magnetic nanoparticles (MNPs) for bacterial capture and concentration is very promising for rapid analysis. When MNPs are functionalized with the proper surface chemistry, they have the ability to bind to bacteria and aid in the removal and concentration of bacteria from a sample for further analysis. This study introduces a novel approach for bacterial concentration using polydopamine (pDA), a highly adhesive polymer often purported to create antibacterial and antibiofouling coatings on medical devices. Although pDA has been generally studied for its ability to coat surfaces and reduce biofilm growth, we have found that when coated on magnetic nanoclusters (MNCs), more specifically iron oxide nanoclusters, it effectively binds to and can remove from suspension some types of bacteria. This study investigated the binding of pDA-coated MNCs (pDA-MNCs) to various Gram-negative and Gram-positive bacteria, including Staphylococcus aureus, Staphylococcus epidermidis, Pseudomonas aeruginosa, and several E. coli strains. MNCs were successfully coated with pDA, and these functionalized MNCs bound a wide variety of bacterial strains. The efficiency of removing bacteria from a suspension can range from 0.99 for S. aureus to 0.01 for an E. coli strain. Such strong capture and differential capture have important applications in collecting bacteria from dilute samples found in medical diagnostics, food and water quality monitoring, and other industries.