Bacterial Fouling Research Articles

Capsaicin mimic-based antifouling and antibacterial polyester nanofiltration membranes with tunable crosslinked structures

Polyester thin-film composite (PE TFC) nanofiltration membranes based on the interfacial polymerization (IP) of polyols/polyphenols and acyl chloride continue to attract considerable attention for textile wastewater treatment due to their excellent antifouling properties. Herein, N-(5-methyl acrylamide-2,3,4 hydroxy benzyl) acrylamide (AMTHBA), a polyphenol-inspired capsaicin derivative, was first utilized as an aqueous monomer for the preparation of antifouling and antibacterial PE TFC membranes via the IP process. The moderate reactivity of AMTHBA and its unique solubility enabled a rational control of the crosslinking density of PE membranes, allowing the formation of structures from loose to dense through an adjustment of the AMTHBA concentration. The densely crosslinked AM-TMC PE membrane exhibited favorable desalination performance, with a water permeance of 21.8 L m−2 h−1 bar−1 and a Na2SO4 rejection of 83.8 %. The loosely crosslinked AM-TMC PE membrane exhibited excellent dye/salt separation performance, with high dye rejections (e.g., 98.5 % for MB) and low salt rejections (e.g., 4.0 % for NaCl), as well as high water permeance (30.4 L m−2 h−1 bar−1). In contrast, the capsaicin-containing PE TFC membranes also demonstrated markedly enhanced resistance to bacterial growth and organic fouling. These findings indicate that AM-TMC PE membranes present novel avenues for the advancement of task-specific separation membranes.

Sulphonated graphene oxide as functionalized filler for polymer electrolyte membrane with enhanced anti-biofouling in microbial fuel cells

This research focuses on the development of a polymer electrolyte membrane (PEM) which is intended to increase power generation while addressing the persistent issue of biofouling in microbial fuel cells (MFC). The central hypothesis of this research work is that a novel PEM made from sulphonated polyether ether ketone (SPEEK) grafted with styrene sulphonic acid (SSA) integrated with sulphonated graphene oxide (SGO) will improve the membrane properties as well as enhance the anti-biofouling effect. The optimal percentage of SSA grafting has been determined based on physicochemical properties of the membrane. Various weight percentages of SGO (2.5, 5, 7.5, & 10 wt%) were introduced to the SPEEK/SSA base polymer to augment the physicochemical properties and also to defend against biofouling. Among the tested membranes, the SPEEK/SSA+5 % SGO composite membrane demonstrates the highest water uptake (106.2±1.9 %) and ion exchange capacity (1.55±0.2 meq g−1). Due to these superior properties, it achieves the maximum power density of 203 mW m−2 and an open circuit voltage (OCV) surpassing 700 mV. The crystal violet assay performed post-MFC operation affirms that the nanocomposite membrane effectively inhibits bacterial fouling. This study positions itself as a solution for long-term, high-performance MFC operations, all while significantly increasing power output and reducing biofouling concerns.

Surface Reconstruction of Silicone-Based Amphiphilic Polymers for Mitigating Marine Biofouling.

Poly(dimethylsiloxane) (PDMS) coatings are considered to be environmentally friendly antifouling coatings. However, the presence of hydrophobic surfaces can enhance the adhesion rate of proteins, bacteria and microalgae, posing a challenge for biofouling removal. In this study, hydrophilic polymer chains were synthesised from methyl methacrylate (MMA), Poly(ethylene glycol) methyl ether methacrylate (PEG-MA) and 3-(trimethoxysilyl) propyl methacrylate (TPMA). The crosslinking reaction between TPMA and PDMS results in the formation of a silicone-based amphiphilic co-network with surface reconstruction properties. The hydrophilic and hydrophobic domains are covalently bonded by condensation reactions, while the hydrophilic polymers migrate under water to induce surface reconstruction and form hydrogen bonds with water molecules to form a dense hydrated layer. This design effectively mitigates the adhesion of proteins, bacteria, algae and other marine organisms to the coating. The antifouling performance of the coatings was evaluated by assessing their adhesion rates to proteins (BSA-FITC), bacteria (B. subtilis and P. ruthenica) and algae (P. tricornutum). The results show that the amphiphilic co-network coating (e.g., P-AM-15) exhibits excellent antifouling properties against protein, bacterial and microalgal fouling. Furthermore, an overall assessment of its antifouling performance and stability was conducted in the East China Sea from 16 May to 12 September 2023, which showed that this silicon-based amphiphilic co-network coating remained intact with almost no marine organisms adhering to it. This study provides a novel approach for the development of high-performance silicone-based antifouling coatings.

Synergetic impact of binary/ternary zeolitic composites on cellulose acetate membranes for potential CO2 removal and antibacterial attributes

The aim of this research is to synthesize multifunctional mixed matrix cellulose acetate (CA) membranes that can provide better CO2/N2 selectivity and will simultaneously fight against bacteria, to immaculate the indoor environment. For that purpose, two different fillers labelled as binary ZnO@Zeolite (1:10, ZZ) and ternary ZnO–CuO@Zeolite (0.8:0.2:10, ZZC) composites have been synthesized via co-precipitation method to entrench into CA matrix with 8 wt% each. The solution mixing technique assisted by thermal evaporation process (TEAP) has been adopted to formulate the desired membranes. Surface morphology, crystalline structure, thermal decomposition, and mechanical properties of novel composites ZZ and ZZC, along with their respective corresponding membranes CA/ZZ-8 and CA/ZZC-8, have been analyzed using field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA), and universal testing machine (UTM). The inclusion of tri-zeolitic composite (ZZC) favors the formation of denser CA membranes, with a smaller crystallite size (10.8 nm), higher thermal stability (%), and a notable increase in mechanical strength (MPa) in contrast to virgin CA as well as bi-zeolitic composite (ZZ) loaded membranes. The selectivity for CO2/N2 separation of tri-zeolitic composite loaded membranes (CA/ZZC-8) is almost six folds higher compared to the pristine CA membrane, whereas it is five folds for bi-zeolitic composite impregnated membrane (CA/ZZ-8). To eradicate bacterial fouling, bi/tri-zeolitic composite loaded membranes are tested against E. coli bacteria by broth culture method and the results validate their antibiotic nature. Synthesized novel CA membranes with hybrid composites provide convenient access towards the development of multipurpose membranes.

Antifouling and antimicrobial 3D printed small household appliances with incorporation of zwitterions and quaternary ammonium compounds

Nowadays, small household appliances had revolutionized the way we live and work with unparalleled innovation and performance, but the bacterial colonization of the appliance surfaces was a widespread phenomenon with consequences on human health and well-being. In this work, a spectrum of composite resins with addition of different ratios of sulfobetaine methacrylate (SBMA) and 12-methacryloyloxydodecylpyridinium bromide (MDPB) were prepared by photocuring 3D printing technology for improving their antifouling and antimicrobial properties. A remarkable improvement in mechanical property was observed as a result of the electrostatic attraction between SBMA, MDPB and polyurethane. The composite resins exhibited a relatively hydrophilic surface because of the high hydration capacity of zwitterionic SBMA, which enabled effective suppression of protein adsorption and bacterial adhesion, resulting in excellent antifouling property. Meanwhile, the antimicrobial property of the composite resins against both S. aureus (Gram-positive bacteria) and E. coli (Gram-negative bacteria) was significantly improved in the presence of MDPB, and the resins with 20% MDPB showed the best antimicrobial property, with a reduction rate of 98.3% and 97.1% against S. aureus and E. coli, respectively. Not only that, all composite resins persevered low cytotoxicity and good biocompatibility. More importantly, a series of children's nebulizers with enhanced protein adsorption resistance, reduced bacterial fouling and sustained biocompatibility were fabricated by photocuring 3D printing technology using the composite resins, confirming the success of antifouling and antimicrobial composite resin strategy in small household appliances.

Preventing Static Biofilm Formation of Staphylococcus aureus on Different Types of Surfaces Using Microbubbles.

Bacterial fouling and biofilm formation on surfaces have been ongoing problems in real life as well as in the medical field. Different approaches have been taken to tackle the issues, from costly surface modification to antibiotic-delivering strategies. In this study, we examined the potential of using stabilized microbubbles (MBs) to shield against bacterial adhesion. Three types of surfaces were tested: hydrophilic glass (hydrophilic surface), neutral hydrophobic polystyrene (PS)-coated surfaces, and negatively charged hydrophobic octadecyltrichlorosilane (OTS)-coated surfaces. By evaluating the colony-forming unit (CFU) values from each surface, MBs stabilized by 0.05 mM SDS were shown to only produce significant reduction of Staphylococcus aureus adhesion on PS surfaces, up to 60.29 and 82.32% compared to no-MB PS surfaces, and no-MB uncoated surfaces, correspondingly, due to the appropriate size, stability, and negative charges of the MB shielding layer. On the other hand, OTS coatings had an intrinsic antiadhesion effect (69.83% compared to uncoated surface), given that the negatively charged OTS-aqueous interface or surface porosity nature of the coating prohibited the attachment of MBs, leading to the elimination of the antifouling effect of MBs. Ultimately, MBs gave better shielding results than surface modification when compared to uncoated surfaces and hence can be applied more widely.

Molecularly imprinted MOF/PAN hybrid nanofibrous membranes for selective bisphenol A adsorption and antibacterial fouling in water treatment

Organic pollutants and microorganisms have become the main challenge in sewage treatment for decades. This mainly results from rapidly developing industry and urbanisation. However, simultaneous clearance of the organic pollutants and microorganisms in water still remains challenging in wastewater treatment. To address this problem, a novel molecularly imprinted metal–organic framework (MOF)/polyacrylonitrile (PAN) hybrid nanofibrous membrane (MOF/PAN-MIM) was prepared for selectively adsorbing bisphenol A (BPA) and inhibiting bacterial fouling in water treatment. Based on the experimental results, the MOF/PAN-MIM showed higher affinity towards BPA as compared to any other organic pollutants and a selective adsorption order of BPA > bisphenol F (BPF) > bisphenol S (BPS) > phenol > nitrophenol > resorcinol with adsorption performance 56.63 mg·g−1. The kinetics and isotherm models of the adsorption of MOF/PAN-MIM towards BPA are best fitted to a pseudo-second-order mode and a Langmuir isotherm. The cyclic reusability of the membranes was demonstrated by the regeneration experiments, with a removal efficiency of 77.73% towards BPA and a negligible Cu ion leakage of 0.64% after six adsorption–desorption cycles. Additionally, the inhibition rate against E. coli and S. aureus was measured to be greater than 90% via the antibacterial assay. The above results indicated that the as-prepared MOF/PAN hybrid nanofibrous membrane has efficient selectivity, sustained cyclic adsorption ability, and antibacterial fouling effect, which can be used as a potential multi-functional filtration membrane in real wastewater treatment.

Betainization of Polydopamine/Polyethylenimine Coating for Universal Zwitterionization.

Biofoulants can adhere to multiple surfaces, degrading the performance of medical devices and industrial facilities and/or causing nosocomial infection. The surface immobilization of zwitterionic materials can prevent the initial attachment of the foulants but lacks extensive implementation. Herein, we propose a facile, universal, two-step surface modification strategy to improve fouling resistance. In the first step, the substrates were immersed in a codeposition solution containing dopamine and branched polyethylenimine (PEI) to form a "primer" layer (PDA/PEI). In the second step, the primer layers were treated with 1,3-propane sultone to betainize primary/secondary/tertiary amine moieties of PEI, generating zwitterions on substrates. After betainization, PS-grafted PDA/PEI (PDA/PEI/S) via a ring-opening alkylation reaction manifested changes in wettability. X-ray photoelectron spectroscopy revealed the presence of zwitterionic moieties on the PDA/PEI/S surfaces. Further investigations using ellipsometry and atomic force microscopy were conducted to scrutinize the relation among the PEI content, film thickness, primer stability, and betainization. As a result, zwitterion-decorated substrates prepared under optimal conditions can exhibit high resistance against bacterial fouling, achieving a 98.5% reduction in bacterial attachment. In addition, the method shows a substrate-independent property, capable of successfully applying it on organic and inorganic substrates. Finally, the newly developed approach shows excellent biocompatibility, displaying no significant difference compared with blank control samples. Overall, we envision that the facile surface modification strategy can further promote the preparation of zwitterion-decorated materials in the future.

Spray-coating of a hydrophobic poly(tetrafluoroethylene) membrane with a copolymer containing sulfobetaine methacrylamide to boost hydration and reduce biofouling in view of improving diabetic wound management and alleviate the immune response

In spite of being an application that tends to be overlooked by membranologists, chronic skin wound healing can be tackled by innovating approaches starring advanced porous membrane materials creating a suitable environment for wound management. Here, we fabricated porous poly(tetrafluoroethylene) membranes decorated with sulfobetaine methacrylamide moieties using a spray-coating method following surface activation by plasma. The zwitterionization permitted to reach improved hydration (WCA of 70°, down from 114°) and quasi-neutral zeta potential (−3 mV up from −68 mV) which rationalized low non-specific protein adsorption (reduced by 88% with fibrinogen), low bacterial and blood fouling (Escherichia coli and whole blood attachment decreased by 98% and 92%, respectively), all the while maintaining very high survival rate of fibroblasts (89%). Improved hydrophilicity and porous features arose in a water vapor transmission rate (>3000 g m−2.day−1) thought to be appropriate to the healing of highly exuding chronic wounds. Applied on skin wounds of diabetic rats, the zwitterionic antifouling biocompatible porous membranes led to faster closure than a commercial dressing (87% vs. 79% after 14 days) by efficiently alleviating the inflammation response. From a histological analysis ran during the inflammation period, infiltrates in the tissue were measured to be 830 ± 240 cells/mm2, against 1507 ± 321 cells/mm2 with the commercial material. Thus, the results of this work demonstrate the benefit of using antifouling porous membranes which reduce the immune response, leading to better and faster healing of chronic wounds. This widens the range of applications for such membranes.

TiO2- geopolymer based novel corrosion protective micro-coatings to emaciate mild steel oxidation in severe environments

Now-a-days, cementitious geopolymer coatings are one of the most studied and adaptable coating systems to combat corrosion on low-carbon steel/structural steel. Due to its green and sustainable nature, it has enormous potential to partially replace traditional organic coatings in terms of corrosion resistant properties and economic aspects. Herein, corrosion protection and antibacterial efficiency of titanium oxide (micro-sized, 5/10/15%) containing sodium aluminosilicate (N-A-S-H) geopolymer coating for mild steel is reported to enhance the lifetime of structural steel. Developed coatings were characterized using XRD, FTIR and FESEM. Characterization results indicated the presence of titanium containing new inorganic phase (Sodium titanium oxide hydrate) along with sodium aluminium hydrate phases in XRD, supported by Ti-O stretching vibrations in FTIR along with Si-O-Al stretching vibrations. Microstructural studies using FESEM indicated the uniform distribution of TiO2 in NA-S-H gel matrix. Results revealed that developed coatings depicted corrosion protective characteristics and exhibited adhesion strength between 16.14 and 17.3 MPa. The scratch resistance test revealed that the coating could bear a point load of greater than 5 kg. Minimum percentage weight change and adhesion loss were observed for coating after immersion in NaCl/H2O for 119 days. An accelerated corrosion test (ASTM B117) was performed in the salt environment for 500 h and the best corrosion protective performance was observed for coating formulation containing 10 % TiO2 with maximum rust grading 5. Electrochemical studies showed better corrosion resistance performance for coating formulation containing 10 % TiO2 as compared to the other two formulations containing 5 and 15% TiO2. The antibacterial efficiency of coatings was evaluated by colony count assay (viability method) against the most commonly found gram-positive bacteria Staphylococcus aureus and one gram-negative bacteria Escherichia coli. All three TiO2-incorporated geopolymer coating formulations revealed a good bacterial reduction in percentage with the best performance observed for coating formulation containing 15% TiO2. The accelerated weathering test (ASTM G154-500 h) was performed to ensure the durability and stability of the developed formation. This study developed a novel, environment-friendly, and lucrative cementitious coating material which is potentially suitable for preventing early oxidation and bacterial fouling of mild steel structures.

Influence of Surface Roughness, Nanostructure, and Wetting on Bacterial Adhesion.

Bacterial fouling is a persistent problem causing the deterioration and failure of functional surfaces for industrial equipment/components; numerous human, animal, and plant infections/diseases; and energy waste due to the inefficiencies at internal and external geometries of transport systems. This work gains new insights into the effect of surface roughness on bacterial fouling by systematically studying bacterial adhesion on model hydrophobic (methyl-terminated) surfaces with roughness scales spanning from ∼2 nm to ∼390 nm. Additionally, a surface energy integration framework is developed to elucidate the role of surface roughness on the energetics of bacteria and substrate interactions. For a given bacteria type and surface chemistry; the extent of bacterial fouling was found to demonstrate up to a 75-fold variation with surface roughness. For the cases showing hydrophobic wetting behavior, both increased effective surface area with increasing roughness and decreased activation energy with increased surface roughness was concluded to enhance the extent of bacterial adhesion. For the cases of superhydrophobic surfaces, the combination of factors including (i) the surpassing of Laplace pressure force of interstitial air over bacterial adhesive force, (ii) the reduced effective substrate area for bacteria wall due to air gaps to have direct/solid contact, and (iii) the reduction of attractive van der Waals force that holds adhering bacteria on the substrate were summarized to weaken the bacterial adhesion. Overall, this study is significant in the context of designing antifouling coatings and systems as well as explaining variations in bacterial contamination and biofilm formation processes on functional surfaces.

Simple bio-inspired coating of ureteral stent for protein and bacterial fouling and calcium encrustation control.

Encrustation, caused by deposition of calcium and magnesium salts present in urine, is a common problem of indwelling urinary devices, such as ureteral stent. Encrustation was also found to be related to urinary tract infections; thus, it is necessary to prepare ureteral stents with antibacterial and antifouling surfaces to mitigate the occurrence of encrustation. In this study, commercial ureteral stent was coated with polydopamine (PDA), formed from self-polymerization of dopamine. The PDA coating was optimized in terms of dopamine concentration, pH, and coating time using response surface methodology. The chosen response parameters for optimization were calcium oxalate (CaC2 O4 ) encrustation and protein adsorption. Optimized PDA coating conditions were determined to be the following: pH9.0, 2mg/mL DA, and 3 days coating. The optimized PDA-coated ureteral stent exhibited outstanding resistance against CaC2 O4 encrustation, protein fouling, and bacterial adhesion due to its hydrophilic and functional coating layer. In comparison with the pristine ureteral stent, PDA coating was able to suppress approximately 97% and 87% of CaC2 O4 and protein adsorption, respectively. The PDA-coated ureteral stent was compared against those of commercially available ureteral stents and found to have superior encrustation and protein fouling mitigation performance. Finally, PDA coating was found to be highly stable for a storage period of 90 days, whether stored in wet or dry conditions.

Bacterial surface attachment and fouling assay on polymer and carbon surfaces using Rheinheimera sp. identified using bacteria community analysis of brackish water

Biofouling on surfaces in contact with sea- or brackish water can severely impact the function of devices like reverse osmosis modules. Single species laboratory assays are frequently used to test new low fouling materials. The choice of bacterial strain is guided by the natural population present in the application of interest and decides on the predictive power of the results. In this work, the analysis of the bacterial community present in brackish water from Mashabei Sadeh, Israel was performed and Rheinheimera sp. was detected as a prominent microorganism. A Rheinheimera strain was selected to establish a short-term accumulation assay to probe initial bacterial attachment as well as biofilm growth to determine the biofilm-inhibiting properties of coatings. Both assays were applied to model coatings, and technically relevant polymers including laser-induced graphene. This strategy might be applied to other water sources to better predict the fouling propensity of new coatings.

Self-Patterned Nanoscale Topography of Thin Copolymer Films Prepared by Evaporative Assembly-Resist Early-Stage Bacterial Adhesion.

Biofilm formation on the surfaces of indwelling medical devices has become a growing health threat due to the development of antimicrobial resistance to infection-causing bacteria. For example, ventilator-associated pneumonia caused by Pseudomonas and Staphylococci species has become a significant concern in treatment of patients during COVID-19 pandemic. Nanostructured surfaces with antifouling activity are of interest as a promising strategy to prevent bacterial adhesion without triggering drug resistance. In this study, we report a facile evaporative approach to prepare block copolymer film coatings with nanoscale topography that resist bacterial adhesion. The initial attachment of the target bacterium Pseudomonas aeruginosa PAO1 to copolymer films as well as homopolymer films was evaluated by fluorescence microscopy. Significant reduction in bacterial adhesion (93-99% less) and area coverage (>92% less) on the copolymer films was observed compared with that on the control and homopolymer films [poly(methacrylic acid) (PMAA)─only 40 and 23% less, respectively]. The surfaces of poly(styrene)-PMAA copolymer films with patterned nanoscale topography that contains sharp peaks ranging from 20 to 80 nm spaced at 30-50 nm were confirmed by atomic force microscopy and the corresponding surface morphology analysis. Investigation of the surface wettability and surface potential of polymer films assists in understanding the effect of surface properties on the bacterial attachment. Comparison of bacterial growth studies in polymer solutions with the growth studies on coatings highlights the importance of physical nanostructure in resisting bacterial adhesion, as opposed to chemical characteristics of the copolymers. Such self-patterned antifouling surface coatings, produced with a straightforward and energy-efficient approach, could provide a convenient and effective method to resist bacterial fouling on the surface of medical devices and reduce device-associated infections.

Recent Progress on Bioinspired Antibacterial Surfaces for Biomedical Application.

Surface bacterial fouling has become an urgent global challenge that calls for resilient solutions. Despite the effectiveness in combating bacterial invasion, antibiotics are susceptible to causing microbial antibiotic resistance that threatens human health and compromises the medication efficacy. In nature, many organisms have evolved a myriad of surfaces with specific physicochemical properties to combat bacteria in diverse environments, providing important inspirations for implementing bioinspired approaches. This review highlights representative natural antibacterial surfaces and discusses their corresponding mechanisms, including repelling adherent bacteria through tailoring surface wettability and mechanically killing bacteria via engineering surface textures. Following this, we present the recent progress in bioinspired active and passive antibacterial strategies. Finally, the biomedical applications and the prospects of these antibacterial surfaces are discussed.

Engineering efficient artificial nanozyme based on chitosan grafted Fe-doped-carbon dots for bacteria biofilm eradication

Bacterial biofilms have evoked worldwide attention owing to their serious threats to public health, but how to effectively eliminate bacterial biofilms still remains great challenges. Here, we rationally designed a novel and vigorous chitosan grafted Fe-doped-carbon dots (CS@Fe/CDs) as an efficient artificial nanozyme to combat rigid bacterial biofilms through the selective activation of Fenton-like reaction-triggered peroxidase-like catalytic activity and the synergistic antibacterial activity of CS. On the one hand, the peroxidase-like catalytic activity made CS@Fe/CDs catalyze H2O2 for producing hydroxyl radicals (•OH), resulting in efficient cleavage of extracellular DNA (eDNA). On the other hand, CS was capable of binding with the negatively charged cell membrane through electrostatic interaction, changing the cell membrane permeability and causing cell death within bacterial biofilms. Based on their synergistic effects, the fragments of bacterial biofilm and exposed bacteria were persistently eradicated. Remarkably, CS@Fe/CDs-based nanozyme not only enabled the effective destroying of gram-positive Staphylococcus aureus (S. aureus) biofilms, but also completely eliminated gram-negative Pseudomonas aeruginosa (P. aeruginosa) biofilms, showing great potential as a promising anti-biofilm agent against bacteria biofilms. This proposed synergistic strategy for bacterial biofilm eradication might offer a powerful modality to manage of bacterial biofilm fouling in food safety and environmental protection.

Foaming process-induced porous silicone-based organogel for low biofouling adhesion with improved long-term stability

Smart lubricant-infused surfaces (LIS) are expected to bring breakthroughs in anti-fouling materials due to their excellent anti-biofouling performance, but the challenges still remain in developing durable LIS. Herein, the structure of LIS is systematically designed, and realized by an inspiration of foaming process, thereby a large lubricant storage capacity and self-replenishing silicone-based organogel coating with improved long-term stability was prepared. The surface of LIS is constructed of micropores, many independent cavities are built inside, and the bottom is bonded to substrate without defects, which is designed to increase the surface lubricant layer stability, lubricant storage capacity and the adhesion to substrate, respectively. Relying on the well-designed structure and the good permeability of silicone oil in PDMS, the lubricant storage capacity reaches 0.2 g/cm2, and the lubricant lost on surface is well replenished from the lubricant stored inside, which makes the local surface damage almost repair within 60 min, and the lubricant retention rate still remains 85% under the 15-day seawater scouring. Further, due to its good stability, after 84 h of bacterial fouling and 25 days of algal fouling, only a few bacteria and algal adhered to the LIS surface, showing an anti-biofouling efficiency close to 99.5%. These design theories, fabricating methods and materials could provide ideas for the development of advanced smart antifouling materials.

Comparative Genome Analysis of the Genus Thiothrix Involving Three Novel Species, Thiothrix subterranea sp. nov. Ku-5, Thiothrix litoralis sp. nov. AS and "Candidatus Thiothrix anitrata" sp. nov. A52, Revealed the Conservation of the Pathways of Dissimilatory Sulfur Metabolism and Variations in the Genetic Inventory for Nitrogen Metabolism and Autotrophic Carbon Fixation.

Two strains of filamentous, colorless sulfur bacteria were isolated from bacterial fouling in the outflow of hydrogen sulfide-containing waters from a coal mine (Thiothrix sp. Ku-5) and on the seashore of the White Sea (Thiothrix sp. AS). Metagenome-assembled genome (MAG) A52 was obtained from a sulfidic spring in the Volgograd region, Russia. Phylogenetic analysis based on the 16S rRNA gene sequences showed that all genomes represented the genus Thiothrix. Based on their average nucleotide identity and digital DNA-DNA hybridization data these new isolates and the MAG represent three species within the genus Thiothrix with the proposed names Thiothrix subterranea sp. nov. Ku-5T, Thiothrix litoralis sp. nov. AST, and “Candidatus Thiothrix anitrata” sp. nov. A52. The complete genome sequences of Thiothrix fructosivorans QT and Thiothrix unzii A1T were determined. Complete genomes of seven Thiothrix isolates, as well as two MAGs, were used for pangenome analysis. The Thiothrix core genome consisted of 1,355 genes, including ones for the glycolysis, the tricarboxylic acid cycle, the aerobic respiratory chain, and the Calvin cycle of carbon fixation. Genes for dissimilatory oxidation of reduced sulfur compounds, namely the branched SOX system (SoxAXBYZ), direct (soeABC) and indirect (aprAB, sat) pathways of sulfite oxidation, sulfur oxidation complex Dsr (dsrABEFHCEMKLJONR), sulfide oxidation systems SQR (sqrA, sqrF), and FCSD (fccAB) were found in the core genome. Genomes differ in the set of genes for dissimilatory reduction of nitrogen compounds, nitrogen fixation, and the presence of various types of RuBisCO.

Polyelectrolyte Complex that Minimizes Bacterial Adhesion to Polyester

AbstractBacterial adhesion is a major concern in the medical field, where bacterial fouling can lead to diminished device efficacy and failure. To combat this, polyelectrolyte complexes (PECs) can be used to modify surfaces to reduce bacterial attachment. In the present study, a water‐based PEC of poly(diallyldimethylammonium chloride) [PDDA] and poly(acrylic acid) are deposited in a simple two‐step process to the surface of polyester fabric. This process includes the deposition of a dissolved mixture of the two polyelectrolytes, followed by the formation of the ionic network through exposure to citric acid buffer. These coatings facilitate the removal of >95% of deposited Staphylococcus aureus after simple rinsing with deionized water. The high degree of surface ionization monitored by FTIR suggests that electrostatic repulsion is responsible for the observed antifouling activity. The morphology of these coatings which is monitored by scanning electron microscope (SEM) and atomic force microscope (AFM) is shown to depend on curing the curing conditions, which suggests that this simple process can be tailored to many applications.

Drawing inspiration from nature to develop anti-fouling coatings: the development of biomimetic polymer surfaces and their effect on bacterial fouling

Abstract The development of self-cleaning biomimetic surfaces has the potential to be of great benefit to human health, in addition to reducing the economic burden on industries worldwide. Consequently, this study developed a biomimetic wax surface using a moulding technique which emulated the topography of the self-cleaning Gladiolus hybridus (Gladioli) leaf. A comparison of topographies was performed for unmodified wax surfaces (control), biomimetic wax surfaces, and Gladioli leaves using optical profilometry and scanning electron microscopy. The results demonstrated that the biomimetic wax surface and Gladioli leaf had extremely similar surface roughness parameters, but the water contact angle of the Gladioli leaf was significantly higher than the replicated biomimetic surface. The self-cleaning properties of the biomimetic and control surfaces were compared by measuring their propensity to repel Escherichia coli and Listeria monocytogenes attachment, adhesion, and retention in mono- and co-culture conditions. When the bacterial assays were carried out in monoculture, the biomimetic surfaces retained fewer bacteria than the control surfaces. However, when using co-cultures of the bacterial species, only following the retention assays were the bacterial numbers reduced on the biomimetic surfaces. The results demonstrate that such surfaces may be effective in reducing biofouling if used in the appropriate medical, marine, and industrial scenarios. This study provides valuable insight into the anti-fouling physical and chemical control mechanisms found in plants, which are particularly appealing for engineering purposes.