Physicochemical regulation of biofilm formation

Colonization characteristics and surface effects of microplastic biofilms: Implications for environmental behavior of typical pollutants

This paper summarizes the colonization dynamics of biofilms on microplastics (MPs) surfaces in aquatic environments, encompassing bacterial characteristics, environmental factors affecting biofilm formation, and matrix types and characteristics. The interaction between biofilm and MPs was also discussed. Through summarizing recent literatures, it was found that MPs surfaces offer numerous benefits to microorganisms, including nutrient enrichment and enhanced resistance to environmental stress. Biofilm colonization changes the surface physical and chemical properties as well as the transport behavior of MPs. At the same time, biofilms also play an important role in the fragmentation and degradation of MPs. In addition, we also investigated the coexistence level, adsorption mechanism, enrichment, and transformation of MPs by environmental pollutants mediated by biofilms. Moreover, an interesting aspect about the colonization of biofilms was discussed. Biofilm colonization not only had a great effect on the accumulation of heavy metals by MPs, but also affects the interaction between particles and environmental pollutants, thereby changing their toxic effects and increasing the difficulty of MPs treatment. Consequently, further attention and research are warranted to delve into the internal mechanisms, environmental risks, and the control of the coexistence of MPs and biofilms.

Microfluidic Platform with Precisely Controlled Hydrodynamic Parameters and Integrated Features for Generation of Microvortices to Accurately Form and Monitor Biofilms in Flow

Microorganisms often live in habitats characterized by fluid flow, and their adhesion to surfaces in industrial systems or clinical settings may lead to pipe clogging, microbially influenced corrosion, material deterioration, food spoilage, infections, and human illness. Here, a novel microfluidic platform was developed to investigate biofilm formation under precisely controlled (i) cell concentration, (ii) temperature, and (iii) flow conditions. The developed platform central unit is a single-channel microfluidic flow cell designed to ensure ultrahomogeneous flow and condition in its central area, where features, e.g., with trapping properties, can be incorporated. In comparison to static and macroflow chamber assays for biofilm studies, microfluidic chips allow in situ monitoring of biofilm formation under various flow regimes and have better environment control and smaller sample requirements. Flow simulations and experiments with fluorescent particles were used to simulate bacteria flow in the platform cell for calculating flow velocity and direction at the microscale level. The combination of flow analysis and fluorescent strain injection in the cell showed that microtraps placed at the center of the channel were efficient in capturing bacteria at determined positions and to study how flow conditions, especially microvortices, can affect biofilm formation. The microfluidic platform exhibited improved performances in terms of homogeneity and robustness for in vitro biofilm formation. We anticipate the presented platform to be suitable for broad, versatile, and high-throughput biofilm studies at the microscale level.

Recent advances in the relationships between biofilms and microplastics in natural environments

Plastic pollution in the form of microplastics (MPs), poses a significant threat to natural ecosystems, with detrimental ecological, social, and economic impacts. This review paper aims to provide an overview of the existing research on the interaction between microbial biofilms and MPs in natural environments. The review begins by outlining the sources and types of MPs, emphasizing their widespread presence in marine, freshwater, and terrestrial ecosystems. It then discusses the formation and characteristics of microbial biofilms on MPs surfaces, highlighting their role in altering the physicochemical properties of MPs and facilitating processes such as vertical transport, biodegradation, dispersion of microorganisms, and gene transfer. Different methods used to assess these interactions are discussed, including microbiological and physicochemical characterization. Current gaps and challenges in understanding the complex relationships between biofilms and MPs are identified, highlighting the need for further research to elucidate the mechanisms underlying these complex interactions and to develop effective mitigation strategies. Innovative solutions, including bioremediation techniques and their combination with other strategies, such as nanotechnology, advanced filtration technologies, and public awareness campaigns, are proposed as promising approaches to address the issue of MPs pollution. Overall, this review underscores the urgent need for a multidisciplinary approach to combating MPs pollution, combining scientific research, technological innovation, and public engagement to safeguard the health and integrity of natural ecosystems.

Targeting bacterial biofilm-related genes with nanoparticle-based strategies

Persistent infection caused by biofilm is an urgent in medicine that should be tackled by new alternative strategies. Low efficiency of classical treatments and antibiotic resistance are the main concerns of the persistent infection due to biofilm formation which increases the risk of morbidity and mortality. The gene expression patterns in biofilm cells differed from those in planktonic cells. One of the promising approaches against biofilms is nanoparticle (NP)-based therapy in which NPs with multiple mechanisms hinder the resistance of bacterial cells in planktonic or biofilm forms. For instance, NPs such as silver (Ag), zinc oxide (ZnO), titanium dioxide (TiO2), copper oxide (Cu), and iron oxide (Fe3O4) through the different strategies interfere with gene expression of bacteria associated with biofilm. The NPs can penetrate into the biofilm structure and affect the expression of efflux pump, quorum-sensing, and adhesion-related genes, which lead to inhibit the biofilm formation or development. Therefore, understanding and targeting of the genes and molecular basis of bacterial biofilm by NPs point to therapeutic targets that make possible control of biofilm infections. In parallel, the possible impact of NPs on the environment and their cytotoxicity should be avoided through controlled exposure and safety assessments. This study focuses on the biofilm-related genes that are potential targets for the inhibition of bacterial biofilms with highly effective NPs, especially metal or metal oxide NPs.

Delignified porous wood as biofilm support for 1,4-dioxane-degrading bacterial consortium

Delignified porous wood samples were used as carriers for biofilm formation of a bacterial consortium with the ability to degrade 1,4-dioxane (DX). The delignification treatment of the natural wood resulted in higher porosity, formation of macropores, increase in surface roughness and hydrophilicity of the treated wood pieces. These superior properties of two types of treated carriers (respectively, A and B) compared to the untreated wood resulted in 2.19 ± 0.52- and 2.66 ± 0.23-fold higher growth of biofilm. Moreover, analysis of the fatty acid profiles indicated an increase in proportion of the saturated fatty acids during the biofilm formation, characterising an enhancement in rigidity and hydrophobicity of the biofilms. DX initial concentration of 100 mg/L was completely degraded (detection limit 0.01 mg/L) in 24 and 32 h using the treated A and B woods, while only 25.84 ± 5.95% was removed after 32 h using the untreated wood. However, fitting the DX biodegradation data to the Monod model showed a lower maximum specific growth rate for biofilm (0.0276 ± 0.0018 1/h) versus planktonic (0.0382 ± 0.0024 1/h), because of gradual accumulation of inactive cells in the biofilm. Findings of this study can contribute to the knowledge of biofilm formation regarding the physical/chemical properties of biofilm carriers and be helpful to the ongoing research on bioremediation of DX.

Metabolic insights from mass spectrometry imaging of biofilms: A perspective from model microorganisms

Biofilms are dense aggregates of bacterial colonies embedded inside a self-produced polymeric matrix. Biofilms have received increasing attention in medical, industrial, and environmental settings due to their enhanced survival. Their characterization using microscopy techniques has revealed the presence of structural and cellular heterogeneity in many bacterial systems. However, these techniques provide limited chemical detail and lack information about the molecules important for bacterial communication and virulence. Mass spectrometry imaging (MSI) bridges the gap by generating spatial chemical information with unmatched chemical detail, making it an irreplaceable analytical platform in the multi-modal imaging of biofilms. In the last two decades, over 30 species of biofilm-forming bacteria have been studied using MSI in different environments. The literature conveys both analytical advancements and an improved understanding of the effects of environmental variables such as host surface characteristics, antibiotics, and other species of microorganisms on biofilms. This review summarizes the insights from frequently studied model microorganisms. We share a detailed list of organism-wide metabolites, commonly observed mass spectral adducts, culture conditions, strains of bacteria, substrate, broad problem definition, and details of the MS instrumentation, such as ionization sources and matrix, to facilitate future studies. We also compared the spatial characteristics of the secretome under different study designs to highlight changes because of various environmental influences. In addition, we highlight the current limitations of MSI in relation to biofilm characterization to enable cross-comparison between experiments. Overall, MSI has emerged to become an important approach for the spatial/chemical characterization of bacterial biofilms and its use will continue to grow as MSI becomes more accessible.

Life at the borderlands: microbiomes of interfaces critical to One Health

Microbiomes are foundational components of the environment that provide essential services relating to food security, carbon sequestration, human health, and the overall well-being of ecosystems. Microbiota exert their effects primarily through complex interactions at interfaces with their plant, animal, and human hosts, as well as within the soil environment. This review aims to explore the ecological, evolutionary, and molecular processes governing the establishment and function of microbiome-host relationships, specifically at interfaces critical to One Health-a transdisciplinary framework that recognizes that the health outcomes of people, animals, plants, and the environment are tightly interconnected. Within the context of One Health, the core principles underpinning microbiome assembly will be discussed in detail, including biofilm formation, microbial recruitment strategies, mechanisms of microbial attachment, community succession, and the effect these processes have on host function and health. Finally, this review will catalogue recent advances in microbiology and microbial ecology methods that can be used to profile microbial interfaces, with particular attention to multi-omic, advanced imaging, and modelling approaches. These technologies are essential for delineating the general and specific principles governing microbiome assembly and functions, mapping microbial interconnectivity across varying spatial and temporal scales, and for the establishment of predictive frameworks that will guide the development of targeted microbiome-interventions to deliver One Health outcomes.

Biofilms on plastic litter in an urban river: Community composition and activity vary by substrate type

In aquatic ecosystems, plastic litter is a substrate for biofilms. Biofilms on plastic and natural surfaces share similar composition and activity, with some differences due to factors such as porosity. In freshwaters, most studies have examined biofilms on benthic substrates, while little research has compared the activity and composition of biofilms on buoyant plastic and natural surfaces. Additionally, the influence of substrate size and successional stage on biofilm composition has not been commonly assessed. We incubated three plastics of distinct textures that are buoyant in rivers, low-density polyethylene (rigid; 1.7 mm thick), low-density polyethylene film (flexible; 0.0254 mm thick), and foamed polystyrene (brittle; 6.5 mm thick), as well as wood substrates (untreated oak veneer; 0.6 mm thick) in the Chicago River. Each material was incubated at three sizes (1, 7.5, and 15 cm2 ). Substrates were incubated at 2-10 cm depths and removed weekly for 6 weeks. On each substrate we measured chlorophyll concentration, biofilm biomass, respiration, and flux of nitrogen gas. We sequenced 16S and 23S rRNA genes at Weeks 1, 3, and 6 to capture biofilm community composition across successional stages. Chlorophyll, biomass, and N2 flux were similar across substrates, but respiration was greater on wood than plastics. Bacterial and algal richness and diversity were highest on foam and wood compared to polyethylene substrates. Bacterial biofilm community composition was distinct between wood and plastic substrates, while the algal community was distinct on wood and foam, which were different from each other and polyethylene substrates. These results indicate that polymer properties influence biofilm alpha and beta diversity, which may affect transport and distribution of plastic pollution and associated microbes, as well as biogeochemical processes in urban rivers. This study provides valuable insights into the effects of substrate on biofilm characteristics, and the ecological impacts of plastic pollution on urban rivers. PRACTITIONER POINTS: Plastic physical and chemical properties act as forces of selection for biofilm. Biofilm activity was similar among three different types of plastic. Community composition between plastic and wood was different.

Black Carbon Impacts on Paraburkholderia xenovorans Strain LB400 Cell Enrichment and Activity: Implications toward Lower-Chlorinated Polychlorinated Biphenyls Biodegradation Potential

Volatilization of lower-chlorinated polychlorinated biphenyls (LC-PCBs) from sediment poses health threats to nearby communities and ecosystems. Biodegradation combined with black carbon (BC) materials is an emerging bioaugmentation approach to remove PCBs from sediment, but development of aerobic biofilms on BC for long-term, sustained LC-PCBs remediation is poorly understood. This work aimed to characterize the cell enrichment and activity of biphenyl- and benzoate-grown Paraburkholderia xenovorans strain LB400 on various BCs. Biphenyl dioxygenase gene (bphA) abundance on four BC types demonstrated corn kernel biochar hosted at least 4 orders of magnitude more attached cells per gram than other feedstocks, and microscopic imaging revealed the attached live cell fraction was >1.5× more on corn kernel biochar than GAC. BC characteristics (i.e., sorption potential, pore size, pH) appear to contribute to cell attachment differences. Reverse transcription qPCR indicated that BC feedstocks significantly influenced bphA expression in attached cells. The bphA transcript-per-gene ratio of attached cells was >10-fold more than suspended cells, confirmed by transcriptomics. RNA-seq also demonstrated significant upregulation of biphenyl and benzoate degradation pathways on attached cells, as well as revealing biofilm formation potential/cell-cell communication pathways. These novel findings demonstrate aerobic PCB-degrading cell abundance and activity could be tuned by adjusting BC feedstocks/attributes to improve LC-PCBs biodegradation potential.

Mechanical constraints to unbound expansion of B. subtilis on semi-solid surfaces

IMPORTANCE

How bacterial cells colonize new territory is a problem of fundamental microbiological and biophysical interest and is key to the emergence of several phenomena of biological, ecological, and medical relevance. Here, we demonstrate how bacteria stuck in a colony of finite size can resume exploration of new territory by aquaplaning and how they fine tune biofilm viscoelasticity to surface material properties that allows them differential mobility. We show how changing local interfacial forces and colony viscosity results in a plethora of bacterial morphologies on surfaces with different physical and mechanical properties.

The effect of polyvinyl chloride (PVC) color on biofilm development and biofilm-heavy metal chemodynamics in the aquatic environment

Plastic surfaces are colonized by microorganisms and biofilms are formed in the natural aquatic environment. As the biofilm develops, it changes the density and buoyancy of the plastic-biofilm complex, results in plastic sinking, and increases the heavy metals accumulated by biofilm's mobility and availability in aquatic ecosystems. In this experiment, biofilms were cultured on five colors of polyvinyl chloride (PVC; transparent, green, blue, red, black) in an aquatic environment to investigate the effects of plastic color on biofilm formation and development (Phase 1) and to study the effects of being sunk below the photic zone on biofilm (Phase 2). The PVC color significantly affected the biofilm formation rate but had no impact on the final biofilm biomass. After sinking the biofilm-PVC below the photic zone in Phase 2, the layer of diatoms on the biofilm surface began to disintegrate, and the biomass and Chlorophyll-a (Chla) content of the biofilm decreased, except on the red PVC. Below the photic zone, the microbial community of the biofilm changed from primarily autotrophic microbes to mostly heterotrophic microbes. Microbial diversity increased and extracellular polymeric substances (EPS) content decreased. The primary factor leading to microbial diversity and community structure changes was water depth rather than PVC color. The changes induced in the biofilm led to an increase in the concentration of all heavy metals in the biofilm, related to the increase in microbial diversity. This study provides new insights into the biofilm formation process and the effects on a biofilm when it sinks below the photic zone.

Polydopamine and calcium functionalized fiber carrier for enhancing microbial attachment and Cr(VI) resistance

The formation of biofilm determines the performance and stability of biofilm system. Increasing the hydrophilicity of the carrier surface could efficiently accelerate the attachment and growth of microorganisms. Here, the surface of polypropylene (PP) fiber carrier was modified with polydopamine (PDA) and calcium (Ca(II)) to enhance microbial attachment and toxicity resistance. The results of surface characteristic confirmed the self-polymerization of PDA and the chelation mechanism of Ca(II). Subsequently, the biofilm formation experiments were conducted in sequencing batch biofilm reactors using both normal and chromium-containing wastewater. The biofilm on the surface of the modified carrier exhibited better nitrogen removal and Cr(VI) reduction ability. The biomass of the modified carrier was significantly increased, and the maximum microbial attachment amounts in normal wastewater and chrome-containing wastewater were 1153.34 and 511.78 mg/g carrier, respectively. Furthermore, the confocal laser scanning microscope (CLSM) indicated that the modified carrier coated with PDA and Ca(II) were both biocompatible, and the cell activity was significantly increased. 16S rRNA sequencing results showed that the modified carrier efficiently enriched both denitrification bacteria (Thauera and Flavobacterium) and chrome-reducing bacteria (Simplicispira and Arenimonas) to improve system stability and Cr(VI) resistance. Microbial phenotype prediction based on BugBase analysis further verified the enrichment effect of modified carriers on microorganisms responsible for biofilm formation and oxidative stress resistance. Overall, this work proposed a novel functional carrier that could provide references for advancing the application of biofilm systems in wastewater treatment.

Nanomaterials-Enabled Physicochemical Antibacterial Therapeutics: Toward the Antibiotic-Free Disinfections

Bacterial infection continues to be an increasing global health problem with the most widely accepted treatment paradigms restricted to antibiotics. However, the overuse and misuse of antibiotics have triggered multidrug resistance of bacteria, frustrating therapeutic outcomes, and leading to higher mortality rates. Even worse, the tendency of bacteria to form biofilms on living and nonliving surfaces further increases the difficulty in confronting bacteria because the extracellular matrix can act as a robust barrier to prevent the penetration of antibiotics and resist environmental damage. As a result, the inability to eliminate bacteria and biofilms often leads to persistent infection, implant failure, and device damage. Therefore, it is of paramount importance to develop alternative antimicrobial agents while avoiding the generation of bacterial resistance to prevent the large-scale growth of bacterial resistance. In recent years, nano-antibacterial materials have played a vital role in the antibacterial field because of their excellent physical and chemical properties. This review focuses on new physicochemical antibacterial strategies and versatile antibacterial nanomaterials, especially the mechanism and types of 2D antibacterial nanomaterials. In addition, this advanced review provides guidance on the development direction of antibiotic-free disinfections in the antibacterial field in the future.

Plastisphere characterization in habitat of the highly endangered Shinisaurus crocodilurus: Bacterial composition, assembly, function and the comparison with surrounding environment

Plastisphere is a new niche for microorganisms that complicate the ecological effects of plastics, and may profoundly influence biodiversity and habitat conservation. The DaGuishan National Nature Reserve, one of the largest habitats of the highly endangered crocodile lizard (Shinisaurus crocodilurus), is experiencing plastic pollution without sufficient attention. Here, plastisphere collected from captive tanks of crocodile lizards in this nature reserve was characterized for the first time. Three types of plastic (PE-PP, PE1, and PE2) together with the surrounding water and soil samples, were collected, and 16S rRNA sequencing technology was used to characterize the bacterial composition. The results demonstrated that plastisphere was driven by stochastic process and had a distinct bacterial community with higher diversity than that in surrounding water (p < 0.05). Bacteria related to nitrogen and carbon cycles (Pseudomonas psychrotolerans, Methylobacterium-Methylorubrum) were more abundant in plastisphere than in water or soil (p < 0.05). More importantly, plastics recruited pathogens and those bacteria function in antibiotic resistant genes (ARGs) coding. Bacteria related to polymer degradation also proliferated in plastisphere, especially Bacillus subtilis with a fold change of 42.01. The PE2 plastisphere, which had the lowest diversity and was dominated by Methylobacterium-Methylorubrum differed from PE 1 and PE-PP plastispheres totally. Plastics' morphology and aquatic nutrient levels contributed to the heterogeneity of different plastispheres. Overall, this study demonstrated that plastispheres diversify in composition and function, affecting ecosystem services directly or indirectly. Pathogens and bacteria related to ARGs expression enriched in the plastisphere should not be ignored because they may threaten the health of crocodile lizards by increasing the risk of infection. Plastic pollution control should be included in conservation efforts for crocodile lizards. This study provides new insights into the potential impacts of plastisphere, which is important for ecological risk assessments of plastic pollution in the habitats of endangered species.

Post-translational modification by the Pgf glycosylation machinery modulates Streptococcus mutans OMZ175 physiology and virulence

Streptococcus mutans is commonly associated with dental caries and the ability to form biofilms is essential for its pathogenicity. We recently identified the Pgf glycosylation machinery of S. mutans, responsible for the post-translational modification of the surface-associated adhesins Cnm and WapA. Since the four-gene pgf operon (pgfS-pgfM1-pgfE-pgfM2) is part of the S. mutans core genome, we hypothesized that the scope of the Pgf system goes beyond Cnm and WapA glycosylation. In silico analyses and tunicamycin sensitivity assays suggested a functional overlap between the Pgf machinery and the rhamnose-glucose polysaccharide synthesis pathway. Phenotypic characterization of pgf mutants (ΔpgfS, ΔpgfE, ΔpgfM1, ΔpgfM2, and Δpgf) revealed that the Pgf system is important for biofilm formation, surface charge, membrane stability, and survival in human saliva. Moreover, deletion of the entire pgf operon (Δpgf strain) resulted in significantly impaired colonization in a rat oral colonization model. Using Cnm as a model, we showed that Cnm is heavily modified with N-acetyl hexosamines but it becomes heavily phosphorylated with the inactivation of the PgfS glycosyltransferase, suggesting a crosstalk between these two post-translational modification mechanisms. Our results revealed that the Pgf machinery contributes to multiple aspects of S. mutans pathobiology that may go beyond Cnm and WapA glycosylation.

Bionanocomposite based on immobilization of Burkholderia cepacian on GO/MOF and its removal of malachite green from river water

Bio-nanocomposites have attracted increasing research attention because they are able to integrate bio- and nano-related functions, and subsequently demonstrate potentially beneficial environmental applications. Here, a functional bionanomaterial based on Burkholderia cepacian (FZ) immobilized on GO/ZIF-8 was developed and used to remove malachite green (MG), with functions based on both biodegradation and adsorption. XRD and FTIR results showed that in situ production of GO/ZIF-8 by combining Zn2+ in ZIF-8 with the carboxyl group on the GO surface, led to FZ immobilized in GO/ZIF-8 through covalent bonding. Zeta analysis showed that the surface of FZ and GO/ZIF-8 had different charges under pH = 9.12, suggesting immobilization also occurred via electrostatic action. BET results confirmed that the specific surface area of GO/ZIF-8 was much larger than that of GO and ZIF-8, but the reduced specific surface area of FZ@GO/ZIF-8 could be due to FZ loading on its surface. The efficiency of FZ@GO/ZIF-8 in the removal of MG reached 99% and furthermore retained good stability after five cycles. The efficiency in removing multiple ions in river water reached more than 80%, which is evidence strongly suggesting that FZ@GO/ZIF-8 is an environmental bionanomaterial with effective application potential.

Combining eugenol and dihydroeugenol with a piperazine moiety to create new antimicrobial agents that are effective against resistant species

Historically, the piperazine moiety has been demonstrated to possess pharmacophoric properties, and has subsequently been incorporated in many drugs that have antitumor, antimalarial, antiviral, antibacterial and antifungal properties. Derivatives of eugenol and dihydroeugenol have also been reported as being bioactive compounds. This study reports the synthesis of a range of eugenol/dihydroeugenol - piperazine derivatives which have been tested as antimicrobial compounds against Gram positive, Gram negative and rapid-growing mycobacteria (RGM). The rationale employed in the design of the structural pattern of these new derivatives, provides useful insights into the structure-activity relationships (SAR) of the series. Antimicrobial activity tests were extremely encouraging, with the majority of the synthesised compounds being more active than eugenol and dihydroeugenol starting materials. The antimicrobial potential was most notable against the Gram-negative species K. pneumoniae and P. aeruginosa, but there was also significant performance against the Gram-positive strains S. epidermidis and S. aureus and the Rapidly Growing Mycobacteria (RGM) strains tested. Tests using the synthesised compounds against multidrug-resistance clinical (MDR) isolates also showed high activity. The biofilm inhibition tests using M. fortuitum showed that all evaluated derivatives were able to inhibit biofilm formation even at low concentrations. In terms of structural-activity relationships; the results generated by this study demonstrate that the compounds with bulky substituents on the piperazine subunit were much more active than those with less bulky groups, or no groups. Importantly, the derivatives with a sulfonamide side chain were the most potent compounds. A further observation was that those compounds with a para-substituted benzenesulfonamide ring stand out, regardless of whether this substituent is a donor or an electron-withdrawing group.

Application of nanomaterials as potential quorum quenchers for disease: Recent advances and challenges

Chemical signal molecules are used by bacteria to interact with one another. Small hormone-like molecules known as autoinducers are produced, released, detected, and responded to during chemical communication. Quorum Sensing (QS) is the word for this procedure; it allows bacterial populations to communicate and coordinate group behavior. Several research has been conducted on using inhibitors to prevent QS and minimize the detrimental consequences. Through the enzymatic breakdown of the autoinducer component, by preventing the formation of autoinducers, or by blocking their reception by adding some compounds (inhibitors) that can mimic the autoinducers, a technique known as "quorum quenching" (QQ) disrupts microbial communication. Numerous techniques, including colorimetry, electrochemistry, bioluminescence, chemiluminescence, fluorescence, chromatography-mass spectroscopy, and many more, can be used to test QS/QQ. They all permit quantitative and qualitative measurements of QS/QQ molecules. The mechanism of QS and QQ, as well as the use of QQ in the prevention of biofilms, are all elaborated upon in this writing, along with the fundamental study of nanoparticle (NP)in QQ. Q.

Progress in Nanostructured Mechano-Bactericidal Polymeric Surfaces for Biomedical Applications

Bacterial infections and antibiotic resistance remain significant contributors to morbidity and mortality worldwide. Despite recent advances in biomedical research, a substantial number of medical devices and implants continue to be plagued by bacterial colonisation, resulting in severe consequences, including fatalities. The development of nanostructured surfaces with mechano-bactericidal properties has emerged as a promising solution to this problem. These surfaces employ a mechanical rupturing mechanism to lyse bacterial cells, effectively halting subsequent biofilm formation on various materials and, ultimately, thwarting bacterial infections. This review delves into the prevailing research progress within the realm of nanostructured mechano-bactericidal polymeric surfaces. It also investigates the diverse fabrication methods for developing nanostructured polymeric surfaces with mechano-bactericidal properties. We then discuss the significant challenges associated with each approach and identify research gaps that warrant exploration in future studies, emphasizing the potential for polymeric implants to leverage their distinct physical, chemical, and mechanical properties over traditional materials like metals.

Interaction between microplastic biofilm formation and antibiotics: Effect of microplastic biofilm and its driving mechanisms on antibiotic resistance gene

As two pollutants with similar transport pathways, microplastics (MPs) and antibiotics (ATs) inevitably co-exist in water environments, and their interaction has become a topic of intense research interest for scholars over the past few years. This paper comprehensively and systematically reviews the current interaction between MPs and ATs, in particular, the role played by biofilm developed MPs (microplastic biofilm). A summary of the formation process of microplastic biofilm and its unique microbial community structure is presented in the paper. The formation of microplastic biofilm can enhance the adsorption mechanisms of ATs on primary MPs. Moreover, microplastic biofilm system is a diverse and vast reservoir of genetic material, and this paper reviews the mechanisms by which microplastics with biofilm drive the production of antibiotic resistance genes (ARGs) and the processes that selectively enrich for more ARGs. Meanwhile, the enrichment of ARGs may lead to the development of microbial resistance and the gradual loss of the antimicrobial effect of ATs. The transfer pathways of ARGs affected by microplastic biofilm are outlined, and ARGs dependent transfer of antibiotic resistance bacteria (ARB) is mainly through horizontal gene transfer (HGT). Furthermore, the ecological implications of the interaction between microplastic biofilm and ATs and perspectives for future research are reviewed. This review contributes to a new insight into the aquatic ecological environmental risks and the fate of contaminants (MPs, ATs), and is of great significance for controlling the combined pollution of these two pollutants.

Overview of strategies to improve the antibacterial property of dental implants

The increasing number of peri-implant diseases and the unsatisfactory results of conventional treatment are causing great concern to patients and medical staff. The effective removal of plaque which is one of the key causes of peri-implant disease from the surface of implants has become one of the main problems to be solved urgently in the field of peri-implant disease prevention and treatment. In recent years, with the advancement of materials science and pharmacology, a lot of research has been conducted to enhance the implant antimicrobial properties, including the addition of antimicrobial coatings on the implant surface, the adjustment of implant surface topography, and the development of new implant materials, and significant progress has been made in various aspects. Antimicrobial materials have shown promising applications in the prevention of peri-implant diseases, but meanwhile, there are some shortcomings, which leads to the lack of clinical widespread use of antimicrobial materials. This paper summarizes the research on antimicrobial materials applied to implants in recent years and presents an outlook on the future development.

Do biosurfactants as anti-biofilm agents have a future in industrial water systems?

Biofilms are bacterial communities embedded in exopolymeric substances that form on the surfaces of both man-made and natural structures. Biofilm formation in industrial water systems such as cooling towers results in biofouling and biocorrosion and poses a major health concern as well as an economic burden. Traditionally, biofilms in industrial water systems are treated with alternating doses of oxidizing and non-oxidizing biocides, but as resistance increases, higher biocide concentrations are needed. Using chemically synthesized surfactants in combination with biocides is also not a new idea; however, these surfactants are often not biodegradable and lead to accumulation in natural water reservoirs. Biosurfactants have become an essential bioeconomy product for diverse applications; however, reports of their use in combating biofilm-related problems in water management systems is limited to only a few studies. Biosurfactants are powerful anti-biofilm agents and can act as biocides as well as biodispersants. In laboratory settings, the efficacy of biosurfactants as anti-biofilm agents can range between 26% and 99.8%. For example, long-chain rhamnolipids isolated from Burkholderia thailandensis inhibit biofilm formation between 50% and 90%, while a lipopeptide biosurfactant from Bacillus amyloliquefaciens was able to inhibit biofilms up to 96% and 99%. Additionally, biosurfactants can disperse preformed biofilms up to 95.9%. The efficacy of antibiotics can also be increased by between 25% and 50% when combined with biosurfactants, as seen for the V9T14 biosurfactant co-formulated with ampicillin, cefazolin, and tobramycin. In this review, we discuss how biofilms are formed and if biosurfactants, as anti-biofilm agents, have a future in industrial water systems. We then summarize the reported mode of action for biosurfactant molecules and their functionality as biofilm dispersal agents. Finally, we highlight the application of biosurfactants in industrial water systems as anti-fouling and anti-corrosion agents.

Pair Interaction between Two Catalytically Active Colloids

Due to the intrinsically complex non-equilibrium behavior of the constituents of active matter systems, a comprehensive understanding of their collective properties is a challenge that requires systematic bottom-up characterization of the individual components and their interactions. For self-propelled particles, intrinsic complexity stems from the fact that the polar nature of the colloids necessitates that the interactions depend on positions and orientations of the particles, leading to a 2d - 1 dimensional configuration space for each particle, in d dimensions. Moreover, the interactions between such non-equilibrium colloids are generically non-reciprocal, which makes the characterization even more complex. Therefore, derivation of generic rules that enable us to predict the outcomes of individual encounters as well as the ensuing collective behavior will be an important step forward. While significant advances have been made on the theoretical front, such systematic experimental characterizations using simple artificial systems with measurable parameters are scarce. Here, two different contrasting types of colloidal microswimmers are studied, which move in opposite directions and show distinctly different interactions. To facilitate the extraction of parameters, an experimental platform is introduced in which these parameters are confined on a 1D track. Furthermore, a theoretical model for interparticle interactions near a substrate is developed, including both phoretic and hydrodynamic effects, which reproduces their behavior. For subsequent validation, the degrees of freedom are increased to 2D motion and resulting trajectories are predicted, finding remarkable agreement. These results may prove useful in characterizing the overall alignment behavior of interacting self-propelling active swimmer and may find direct applications in guiding the design of active-matter systems involving phoretic and hydrodynamic interactions.

The Heterogeneous Diffusion of Polystyrene Nanoparticles and the Effect on the Expression of Quorum-Sensing Genes and EPS Production as a Function of Particle Charge and Biofilm Age

Biofilms are abundantly present in both natural and engineered environmental systems and will likely influence broader particle fate and transport phenomena. While some developed models describe the interactions between nanoparticles and biofilms, studies are only beginning to uncover the complexity of nanoparticle diffusion patterns. With the knowledge of the nanoparticle potential to influence bacterial processes, more systematic studies are needed to uncover the dynamics of bacteria-nanoparticle interactions. This study explored specific microbial responses to nanoparticles and the heterogeneity of nanoparticle diffusion. Pseudomonas aeruginosa biofilms (cultivated for 48 and 96 hours, representing early and late stages of development) were exposed to charged (aminated and carboxylated) polystyrene nanoparticles. With a combination of advanced fluorescence microscopy and real time quantitative PCR, we characterized the diffusion of polystyrene nanoparticles in P. aeruginosa biofilms and evaluated how biofilms respond to the presence of nanoparticles in terms of the expression of key EPS production-associated genes (pelA and rpsL) and quorum-sensing associated (lasR) genes. Our findings show that nanoparticle diffusion coefficients are independent of the particle surface charge only in mature biofilms and that the presence of nanoparticles influences bacterial gene expression. Independent of the particle's charge polystyrene nanoparticles down-regulated pelA in mature biofilms. By contrast, charge-specific responses were identified in lasR and rpsL gene expression. The targeted genes expression analysis and heterogeneous diffusion models demonstrate that particle charge influences nanoparticle mobility and provides significant insight into the intrinsic structural heterogeneity of P. aeruginosa biofilms. These findings suggest that biofilm maturity and particle charge are essential factors to consider when evaluating the transport of nanoparticles within a biofilm matrix.

Phase transitions on a multiplex of swarmalators

Dynamics of bidirectionally coupled swarmalators subject to attractive and repulsive couplings is analyzed. The probability of two elements in different layers being connected strongly depends on a defined vision range r_{c} which appears to lead both layers in different patterns while varying its values. Particularly, the interlayer static sync π has been found and its stability is proven. First-order transitions are observed when the repulsive coupling strength σ_{r} is very small for a fixed r_{c} and, moreover, in the absence of the repulsive coupling, they also appear for sufficiently large values of r_{c}. For σ_{r}=0 and for sufficiently small values of r_{c}, both layers achieve a second-order transition in a surprising two steps that are characterized by the drop of the energy of the internal phases while increasing the value of the interlayer attractive coupling σ_{a} and later a smooth jump, up to high energy value where synchronization is achieved. During these transitions, the internal phases present rotating waves with counterclockwise and later clockwise directions until synchronization, as σ_{a} increases. These results are supported by simulations and animations added as supplemental materials.

Bacterial biofilms in the human body: prevalence and impacts on health and disease

Bacterial biofilms can be found in most environments on our planet, and the human body is no exception. Consisting of microbial cells encased in a matrix of extracellular polymers, biofilms enable bacteria to sequester themselves in favorable niches, while also increasing their ability to resist numerous stresses and survive under hostile circumstances. In recent decades, biofilms have increasingly been recognized as a major contributor to the pathogenesis of chronic infections. However, biofilms also occur in or on certain tissues in healthy individuals, and their constituent species are not restricted to canonical pathogens. In this review, we discuss the evidence for where, when, and what types of biofilms occur in the human body, as well as the diverse ways in which they can impact host health under homeostatic and dysbiotic states.

Can Graphene Pave the Way to Successful Periodontal and Dental Prosthetic Treatments? A Narrative Review

Graphene, as a promising material, holds the potential to significantly enhance the field of dental practices. Incorporating graphene into dental materials imparts enhanced strength and durability, while graphene-based nanocomposites offer the prospect of innovative solutions such as antimicrobial dental implants or scaffolds. Ongoing research into graphene-based dental adhesives and composites also suggests their capacity to improve the quality and reliability of dental restorations. This narrative review aims to provide an up-to-date overview of the application of graphene derivatives in the dental domain, with a particular focus on their application in prosthodontics and periodontics. It is important to acknowledge that further research and development are imperative to fully explore the potential of graphene and ensure its safe use in dental practices.

Epidemic Trends and Biofilm Formation Mechanisms of Haemophilus influenzae: Insights into Clinical Implications and Prevention Strategies

Haemophilus influenzae (H. influenzae) is a significant pathogen responsible for causing respiratory tract infections and invasive diseases, leading to a considerable disease burden. The Haemophilus influenzae type b (Hib) conjugate vaccine has notably decreased the incidence of severe infections caused by Hib strains, and other non-typable H. influenzae (NTHi) serotypes have emerged as epidemic strains worldwide. As a result, the global epidemic trends and antibiotic resistance characteristics of H. influenzae have been altered. Researches on the virulence factors of H. influenzae, particularly the mechanisms underlying biofilm formation, and the development of anti-biofilm strategies hold significant clinical value. This article provides a summary of the epidemic trends, typing methods, virulence factors, biofilm formation mechanisms, and prevention strategies of H. influenzae. The increasing prevalence of NTHi strains and antibiotic resistance among H. influenzae, especially the high β-lactamase positivity and the emergence of BLNAR strains have increased clinical difficulties. Understanding its virulence factors, especially the formation mechanism of biofilm, and formulating effective anti-biofilm strategies may help to reduce the clinical impact. Therefore, future research efforts should focus on developing new approaches to prevent and control H. influenzae infections.

A Study on Bio-Stabilisation of Sub-Standard Soil by Indigenous Soil Urease-Producing Bacteria

Sub-standard soils are of great concern worldwide due to diverse economic losses and the possibility of severe environmental hazards ranging from catastrophic landslides, building collapse, and erosion to loss of lives and properties. This study explored the potential of urease-producing bacteria, <i>Bacillus cereus</i> and <i>Bacillus paramycoides</i>, to stabilise sub-standard soil bio-stabilisation. The maximum urease activity measured by <i>B. cereus</i> and <i>B. paramycoides</i> was 665 U/mL and 620 U/mL, respectively. <i>B. cereus</i> and <i>B. paramycoides</i> precipitated 943 ± 57 mg/L and 793 ± 51 mg/L of CaCO₃ at an optical density (425 nm) of 1.01 and 1.09 and pH 8.83 and 8.59, respectively, after 96 hours of incubation. SEM microstructural analysis of the precipitated CaCO₃ revealed crystals of various sizes (2.0–23.0 µm) with different morphologies. XRD analysis confirmed that the precipitated CaCO₃ comprised calcite and aragonite crystals. SEM analysis of the microstructure of organic and sandy clay soils treated with <i>B. cereus</i> and <i>B. paramycoides</i> showed the formation of bio-precipitated calcium carbonate deposits on the soil particles (biocementing soil grains), with <i>B. cereus</i> precipitating more CaCO₃ crystals with a better biocementing effect compared to <i>B. paramycoides</i>. Overall, the experimental results attributed CaCO₃ formation to bacterial-associated processes, suggesting that soil ureolytic bacteria are potentially useful to stabilise sub-standard soil.

Bacterial Biofilm Formation on Biomaterials and Approaches to Its Treatment and Prevention

Bacterial biofilms can cause widespread infection. In addition to causing urinary tract infections and pulmonary infections in patients with cystic fibrosis, biofilms can help microorganisms adhere to the surfaces of various medical devices, causing biofilm-associated infections on the surfaces of biomaterials such as venous ducts, joint prostheses, mechanical heart valves, and catheters. Biofilms provide a protective barrier for bacteria and provide resistance to antimicrobial agents, which increases the morbidity and mortality of patients. This review summarizes biofilm formation processes and resistance mechanisms, as well as the main features of clinically persistent infections caused by biofilms. Considering the various infections caused by clinical medical devices, we introduce two main methods to prevent and treat biomaterial-related biofilm infection: antibacterial coatings and the surface modification of biomaterials. Antibacterial coatings depend on the covalent immobilization of antimicrobial agents on the coating surface and drug release to prevent and combat infection, while the surface modification of biomaterials affects the adhesion behavior of cells on the surfaces of implants and the subsequent biofilm formation process by altering the physical and chemical properties of the implant material surface. The advantages of each strategy in terms of their antibacterial effect, biocompatibility, limitations, and application prospects are analyzed, providing ideas and research directions for the development of novel biofilm infection strategies related to therapeutic materials.

Microfluidics for Biofilm Studies

Biofilms are multicellular communities held together by a self-produced extracellular matrix and exhibit a set of properties that distinguish them from free-living bacteria. Biofilms are exposed to a variety of mechanical and chemical cues resulting from fluid motion and mass transport. Microfluidics provides the precise control of hydrodynamic and physicochemical microenvironments to study biofilms in general. In this review, we summarize the recent progress made in microfluidics-based biofilm research, including understanding the mechanism of bacterial adhesion and biofilm development, assessment of antifouling and antimicrobial properties, development of advanced in vitro infection models, and advancement in methods to characterize biofilms. Finally, we provide a perspective on the future direction of microfluidics-assisted biofilm research.

Development of Antifouling Strategies for Marine Applications

Marine biofouling is an undeniable challenge for aquatic systems since it is responsible for several environmental and ecological problems and economic losses. Several strategies have been developed to mitigate fouling-related issues in marine environments, including developing marine coatings using nanotechnology and biomimetic models, and incorporating natural compounds, peptides, bacteriophages, or specific enzymes on surfaces. The advantages and limitations of these strategies are discussed in this review, and the development of novel surfaces and coatings is highlighted. The performance of these novel antibiofilm coatings is currently tested by in vitro experiments, which should try to mimic real conditions in the best way, and/or by in situ tests through the immersion of surfaces in marine environments. Both forms present their advantages and limitations, and these factors should be considered when the performance of a novel marine coating requires evaluation and validation. Despite all the advances and improvements against marine biofouling, progress toward an ideal operational strategy has been slow given the increasingly demanding regulatory requirements. Recent developments in self-polishing copolymers and fouling-release coatings have yielded promising results which set the basis for the development of more efficient and eco-friendly antifouling strategies.

Efflux pumps and microbial biofilm formation

Biofilm-related infections are resistant forms of pathogens that are regarded as a medical problem, particularly due to the spread of multiple drug resistance. One of the factors associated with biofilm drug resistance is the presence of various types of efflux pumps in bacteria. Efflux pumps also play a role in biofilm formation by influencing Physical-chemical interactions, mobility, gene regulation, quorum sensing (QS), extracellular polymeric substances (EPS), and toxic compound extrusion. According to the findings of studies based on efflux pump expression analysis, their role in the anatomical position within the biofilm will differ depending on the biofilm formation stage, encoding gene expression level, the type and concentration of substrate. In some cases, the function of the efflux pumps can overlap with each other, so it seems necessary to accurate identify the efflux pumps of biofilm-forming bacteria along with their function in this process. Such studies will help to choose treatment strategy, at least in combination with antibiotics. Furthermore, if the goal of treatment is an efflux pump manipulation, we should not limit it to inhibition.

Physiological consequences of inactivation of lgmB and lpxL1, two genes involved in lipid A synthesis in Bordetella bronchiseptica

To develop a Bordetella bronchiseptica vaccine with reduced endotoxicity, we previously inactivated lpxL1, the gene encoding the enzyme that incorporates a secondary 2-hydroxy-laurate in lipid A. The mutant showed a myriad of phenotypes. Structural analysis showed the expected loss of the acyl chain but also of glucosamine (GlcN) substituents, which decorate the phosphates in lipid A. To determine which structural change causes the various phenotypes, we inactivated here lgmB, which encodes the GlcN transferase, and lpxL1 in an isogenic background and compared the phenotypes. Like the lpxL1 mutation, the lgmB mutation resulted in reduced potency to activate human TLR4 and to infect macrophages and in increased susceptibility to polymyxin B. These phenotypes are therefore related to the loss of GlcN decorations. The lpxL1 mutation had a stronger effect on hTLR4 activation and additionally resulted in reduced murine TLR4 activation, surface hydrophobicity, and biofilm formation, and in a fortified outer membrane as evidenced by increased resistance to several antimicrobials. These phenotypes, therefore, appear to be related to the loss of the acyl chain. Moreover, we determined the virulence of the mutants in the Galleria mellonella infection model and observed reduced virulence of the lpxL1 mutant but not of the lgmB mutant.

Cationic Microbubbles for Non-Selective Binding of Cavitation Nuclei to Bacterial Biofilms

The presence of multi-drug resistant biofilms in chronic, persistent infections is a major barrier to successful clinical outcomes of therapy. The production of an extracellular matrix is a characteristic of the biofilm phenotype, intrinsically linked to antimicrobial tolerance. The heterogeneity of the extracellular matrix makes it highly dynamic, with substantial differences in composition between biofilms, even in the same species. This variability poses a major challenge in targeting drug delivery systems to biofilms, as there are few elements both suitably conserved and widely expressed across multiple species. However, the presence of extracellular DNA within the extracellular matrix is ubiquitous across species, which alongside bacterial cell components, gives the biofilm its net negative charge. This research aims to develop a means of targeting biofilms to enhance drug delivery by developing a cationic gas-filled microbubble that non-selectively targets the negatively charged biofilm. Cationic and uncharged microbubbles loaded with different gases were formulated and tested to determine their stability, ability to bind to negatively charged artificial substrates, binding strength, and, subsequently, their ability to adhere to biofilms. It was shown that compared to their uncharged counterparts, cationic microbubbles facilitated a significant increase in the number of microbubbles that could both bind and sustain their interaction with biofilms. This work is the first to demonstrate the utility of charged microbubbles for the non-selective targeting of bacterial biofilms, which could be used to significantly enhance stimuli-mediated drug delivery to the bacterial biofilm.

Response of microbial communities to nutrient removal in coastal sediment by using ecological concrete

Ecological concrete (eco-concrete) is a kind of environment-friendly material with porous characteristics. In this study, the eco-concrete was used to remove the total nitrogen (TN), total phosphorus (TP), and total organic carbon (TOC) in marine coastal sediment. The bacterial communities in sediment and on eco-concrete surface were also investigated by using high-throughput sequencing and quantitative PCR of 16S rRNA gene. We found that the mean removal efficiencies of TN, TP, and TOC in treatment group were 8.3%, 8.4%, and 12.3% after 28 days. The bacterial community composition in the treatment group was significantly different from that in the control group on day 28. In addition, the bacterial community composition on eco-concrete surface was slightly different from that in sediment, and the copy numbers of 16S rRNA gene were higher on eco-concrete surface than in sediment. The types of eco-concrete aggregates (gravel, pebble, and zeolite) also had effects on the bacterial community composition and 16S rRNA gene copy numbers. Furthermore, we found the abundant genus Sulfurovum increased significantly on eco-concrete surface in the treatment group after 28 days. Bacteria belonging to this genus were found having denitrification ability and were commonly detected in bioreactors for nitrate removal. Overall, our study expands the application scopes of eco-concrete and suggests that the bacterial communities in eco-concrete can potentially enhance the removal efficiency of nutrients in coastal sediment.

Interactions between Macrophages and Biofilm during Staphylococcus aureus-Associated Implant Infection: Difficulties and Solutions

Staphylococcus aureus (S. aureus) biofilm is the major cause of failure of implant infection treatment that results in heavy social and economic burden on individuals, families, and communities. Planktonic S. aureus attaches to medical implant surfaces where it proliferates and is wrapped by extracellular polymeric substances, forming a solid and complex biofilm. This provides a stable environment for bacterial growth, infection maintenance, and diffusion and protects the bacteria from antimicrobial agents and the immune system of the host. Macrophages are an important component of the innate immune system and resist pathogen invasion and infection through phagocytosis, antigen presentation, and cytokine secretion. The persistence, spread, or clearance of infection is determined by interplay between macrophages and S. aureus in the implant infection microenvironment. In this review, we discuss the interactions between S. aureus biofilm and macrophages, including the effects of biofilm-related bacteria on the macrophage immune response, roles of myeloid-derived suppressor cells during biofilm infection, regulation of immune cell metabolic patterns by the biofilm environment, and immune evasion strategies adopted by the biofilm against macrophages. Finally, we summarize the current methods that support macrophage-mediated removal of biofilms and emphasize the importance of considering multi-dimensions and factors related to implant-associated infection such as immunity, metabolism, the host, and the pathogen when developing new treatments.

Functionalization of 3D Printed Scaffolds Using Polydopamine and Silver Nanoparticles for Bone-Interfacing Applications

The prevention of bacterial colonization and the stimulation of osseointegration are two major requirements for bone-interfacing materials to reduce the incidence of complications and promote the restoration of the patient's health. The present investigation developed an effective, two-step functionalization of 3D printed scaffolds intended for bone-interfacing applications using a simple polydopamine (PDA) dip-coating method followed by the formation of silver nanoparticles (AgNPs) after a second coating step in silver nitrate. 3D printed polymeric substrates coated with a ∼20 nm PDA layer and 70 nm diameter AgNPs proved effective in hindering Staphylococcus aureus biofilm formation, with a 3000-8000-fold reduction in the number of bacterial colonies formed. The implementation of porous geometries significantly accelerated osteoblast-like cell growth. Microscopy characterization further elucidated homogeneity, features, and penetration of the coating inside the scaffold. A proof-of-concept coating on titanium substrates attests to the transferability of the method to other materials, broadening the range of applications both in and outside the medical sector. The antibacterial efficiency of the coating is likely to lead to a decrease in the number of bacterial infections developed after surgery in the presence of these coatings on prosthetics, thus translating to a reduction in revision surgeries and improved health outcomes.

Biofilm Formation and Control of Foodborne Pathogenic Bacteria

Biofilms are microbial aggregation membranes that are formed when microorganisms attach to the surfaces of living or nonliving things. Importantly, biofilm properties provide microorganisms with protection against environmental pressures and enhance their resistance to antimicrobial agents, contributing to microbial persistence and toxicity. Thus, bacterial biofilm formation is part of the bacterial survival mechanism. However, if foodborne pathogens form biofilms, the risk of foodborne disease infections can be greatly exacerbated, which can cause major public health risks and lead to adverse economic consequences. Therefore, research on biofilms and their removal strategies are very important in the food industry. Food waste due to spoilage within the food industry remains a global challenge to environmental sustainability and the security of food supplies. This review describes bacterial biofilm formation, elaborates on the problem associated with biofilms in the food industry, enumerates several kinds of common foodborne pathogens in biofilms, summarizes the current strategies used to eliminate or control harmful bacterial biofilm formation, introduces the current and emerging control strategies, and emphasizes future development prospects with respect to bacterial biofilms.

Microalgae colonization and trace element accumulation on the plastisphere of marine plastic debris in Monastir Bay (Eastern Tunisia)

In this study, we examined the toxicity potential of the epiplastic microalgal community that developed on low-density polyethylene (LD-PE) plastic debris found in two distinct regions of the Monastir Bay (Tunisia): the coast exposed to anthropogenic discharges and the open sea in front of the Kuriat Islands. Concentrations of potentially toxic elements (PTEs) accumulated in sediments and plastisphere were compared in order to determine their toxicity potential to biological life. The collected plastispheres were predominantly composed of cyanobacteria, chlorophytes, and diatoms. Diatoms display a relatively high diversity (25 species). At all stations, potentially harmful microalgae (PHM) were more abundant in the plastisphere than in seawater and the coastal zone seems to harbour increased number of potentially harmful cyanobacteria within the plastisphere. At the offshore station S1, the PHM community was dominated by the potentially harmful diatoms belonging to the genus Pseudo-nitzschia. Phormidium sp. was the main potentially harmful cyanobacterium identified in the plastisphere of S1. PTEs concentration in the plastisphere was higher than in sediment and ranking with very high contamination factors at all sites according to the sequence Pb > Cu > Cd > Ni > Zn. The highest accumulation of PTEs in the plastisphere was recorded near harbors and industrial zones with important human interference. This work shows that plastisphere can be a threat to vulnerable species not only because it can contain PHM but also because it can accumulate PTEs.

Larval Therapy and Larval Excretions/Secretions: A Potential Treatment for Biofilm in Chronic Wounds? A Systematic Review

Chronic wounds present a global healthcare challenge and are increasing in prevalence, with bacterial biofilms being the primary roadblock to healing in most cases. A systematic review of the to-date knowledge on larval therapy's interaction with chronic-wound biofilm is presented here. The findings detail how larval therapy-the controlled application of necrophagous blowfly larvae-acts on biofilms produced by chronic-wound-relevant bacteria through their principle pharmacological mode of action: the secretion and excretion of biologically active substances into the wound bed. A total of 12 inclusion-criteria-meeting publications were identified following the application of a PRISMA-guided methodology for a systematic review. The findings of these publications were qualitatively analyzed to provide a summary of the prevailing understanding of larval therapy's effects on bacterial biofilm. A further review assessed the quality of the existing evidence to identify knowledge gaps and suggest ways these may be bridged. In summary, larval therapy has a seemingly unarguable ability to inhibit and degrade bacterial biofilms associated with impaired wound healing. However, further research is needed to clarify and standardize the methodological approach in this area of investigation. Such research may lead to the clinical application of larval therapy or derivative treatments for the management of chronic-wound biofilms and improve patient healing outcomes at a time when alternative therapies are desperately needed.

Nature-Inspired Surface Structures Design for Antimicrobial Applications

Surface contamination by microorganisms such as viruses and bacteria may simultaneously aggravate the biofouling of surfaces and infection of wounds and promote cross-species transmission and the rapid evolution of microbes in emerging diseases. In addition, natural surface structures with unique anti-biofouling properties may be used as guide templates for the development of functional antimicrobial surfaces. Further, these structure-related antimicrobial surfaces can be categorized into microbicidal and anti-biofouling surfaces. This review introduces the recent advances in the development of microbicidal and anti-biofouling surfaces inspired by natural structures and discusses the related antimicrobial mechanisms, surface topography design, material application, manufacturing techniques, and antimicrobial efficiencies.

Effect of hydrodynamics on the transformation of nitrogen in river water by regulating the mass transfer performance of dissolved oxygen in biofilm

Biofilms drive crucial ecosystem processes in rivers. This study provided the basis for overall quantitative calculations about the contribution of biofilms to the nitrogen cycle. At the early stage of biofilm formation, dissolved oxygen (DO) could penetrate the biofilms. As the biofilm grew and the thickness increased, then the mass transfer of DO was restricted. The microaerobic layer firstly appeared in biofilm under the turbulent flow conditions, with the appearance of the microaerobic and anaerobic layer, the nitrification and denitrification reaction could proceed smoothly in biofilm. And the removal efficiency of total nitrogen (TN) increased as the biofilm matured. Under the turbulent flow conditions, mature biofilms had the smallest thickness, but the highest proportion the anaerobic layer to the biofilm thickness, the highest density, and the highest nitrogen removal efficiency. However, the nitrogen removal efficiency of biofilm was the lowest under laminar flow conditions. The difference of layered structure of biofilm and the DO flux in biofilm explained the difference of nitrogen migration and transformation in river water under different hydrodynamic conditions. This study would help control the growth of biofilm and improve the nitrogen removal capacity of biofilm by regulating hydrodynamic conditions.

Porous Pellicle Formation of a Filamentous Bacterium, Leptothrix

The bacterium Leptothrix cholodnii generates filaments encased in a sheath comprised of woven nanofibrils. In static liquid culture, L. cholodnii moves toward the air-liquid interface, where it forms porous pellicles. Observations of aggregation at the interface reveal that clusters consisting of only a few bacteria primarily grow by netting free cells. These growing clusters hierarchically enlarge through the random docking of other small clusters. We find that the bacteria swim using their polar flagellum toward the interface, where their sheath assists them in intertwining with others and thereby promotes the formation of small clusters. In contrast, sheathless hydrophobic mutant cells get stuck to the interface. We find that the nanofibril sheath is vital for robust pellicle formation as it lowers cell surface hydrophobicity by 60%, thereby reducing their adsorption and enabling cells to move toward and stick together at the air-liquid interface. IMPORTANCE Efficient and sustainable management of water resources is becoming a fundamental issue for supporting growing populations and for developing economic activity. Fundamental to this management is the treatment of wastewater. Microorganisms are the active component of activated sludge that is employed in the biodegradation process of many wastewater treatment facilities. However, uncontrolled growth of filamentous bacteria such as Sphaerotilus often results in filamentous bulking, lowering the efficiency of water treatment systems. To prevent this undesirable condition, strategies based on a fundamental understanding of the ecology of filamentous bacteria are required. Although the filamentous bacterium Leptothrix cholodnii, which is closely related to Sphaerotilus, is a minor inhabitant of activated sludge, its complete genome sequence is known, making gene manipulation relatively easy. Moreover, L. cholodnii generates porous pellicles under static conditions, which may be a characteristic of filamentous bulking. We show that both swimming motility and nanofibril-mediated air-liquid interface attachment are required for porous pellicle formation. These insights are critical for a better understanding of the characteristics of filamentous bulking and might improve strategies to control activated sludge.

Genetic and compositional analysis of biofilm formed by Staphylococcus aureus isolated from food contact surfaces

INTRODUCTION

Staphylococcus aureus is an important pathogen that can form biofilms on food contact surfaces (FCS) in the dairy industry, posing a serious food safety, and quality concern. Biofilm is a complex system, influenced by nutritional-related factors that regulate the synthesis of the components of the biofilm matrix. This study determines the prevalence of biofilm-associated genes and evaluates the development under different growth conditions and compositions of biofilms produced by S. aureus.

METHODS

Biofilms were developed in TSB, TSBG, TSBNaCl, and TSBGNaCl on stainless-steel (SS), with enumeration at 24 and 192 h visualized by epifluorescence and scanning electron microscopy (SEM). The composition of biofilms was determined using enzymatic and chemical treatments and confocal laser scanning microscopy (CLSM).

RESULTS AND DISCUSSION

A total of 84 S. aureus (SA1-SA84) strains were collected from 293 dairy industry FCS (FCS-stainless steel [n = 183] and FCS-polypropylene [n = 110]) for this study. The isolates harbored the genes sigB (66%), sar (53%), agrD (52%), clfB/clfA (38%), fnbA/fnbB (20%), and bap (9.5%). 99. In particular, the biofilm formed by bap-positive S. aureus onto SS showed a high cell density in all culture media at 192 h in comparison with the biofilms formed at 24 h (p < 0.05). Epifluorescence microscopy and SEM revealed the metabolically active cells and the different stages of biofilm formation. CLSM analysis detected extracellular polymeric of S. aureus biofilms on SS, such as eDNA, proteins, and polysaccharides. Finally, the level of detachment on being treated with DNase I (44.7%) and NaIO 4(42.4%) was greater in the biofilms developed in TSB compared to culture medium supplemented with NaCl at 24 h; however, there was no significant difference when the culture medium was supplemented with glucose. In addition, after treatment with proteinase K, there was a lower level of biomass detachment (17.7%) of the biofilm developed in TSBNaCl (p < 0.05 at 24 h) compared to that in TSB, TSBG, and TSBGNaCl (33.6, 36.9, and 37.8%, respectively). These results represent a deep insight into the composition of S. aureus biofilms present in the dairy industry, which promotes the development of more efficient composition-specific disinfection strategies.

In vitro testing and efficacy of poly-lactic acid coating incorporating antibiotic loaded coralline bioceramic on Ti6Al4V implant against Staphylococcus aureus

Biofilm formation on an implant surface is most commonly caused by the human pathogenic bacteria Staphylococcus aureus, which can lead to implant related infections and failure. It is a major problem for both implantable orthopedic and maxillofacial devices. The current antibiotic treatments are typically delivered orally or in an injectable form. They are not highly effective in preventing or removing biofilms, and they increase the risk of antibiotic resistance of bacteria and have a dose-dependent negative biological effect on human cells. Our aim was to improve current treatments via a localized and controlled antibiotic delivery-based implant coating system to deliver the antibiotic, gentamicin (Gm). The coating contains coral skeleton derived hydroxyapatite powders (HAp) that act as antibiotic carrier particles and have a biodegradable poly-lactic acid (PLA) thin film matrix. The system is designed to prevent implant related infections while avoiding the deleterious effects of high concentration antibiotics in implants on local cells including primary human adipose derived stem cells (ADSCs). Testing undertaken in this study measured the rate of S. aureus biofilm formation and determined the growth rate and proliferation of ADSCs. After 24 h, S. aureus biofilm formation and the percentage of live cells found on the surfaces of all 5%-30% (w/w) PLA-Gm-(HAp-Gm) coated Ti6Al4V implants was lower than the control samples. Furthermore, Ti6Al4V implants coated with up to 10% (w/w) PLA-Gm-(HAp-Gm) did not have noticeable Gm related adverse effect on ADSCs, as assessed by morphological and surface attachment analyses. These results support the use and application of the antibacterial PLA-Gm-(HAp-Gm) thin film coating design for implants, as an antibiotic release control mechanism to prevent implant-related infections.

Design strategies for adhesive hydrogels with natural antibacterial agents as wound dressings: Status and trends

The wound healing process is usually susceptible to different bacterial infections due to the complex physiological environment, which significantly impairs wound healing. The topical application of antibiotics is not desirable for wound healing because the excessive use of antibiotics might cause bacteria to develop resistance and even the production of super bacteria, posing significant harm to human well-being. Wound dressings based on adhesive, biocompatible, and multi-functional hydrogels with natural antibacterial agents have been widely recognized as effective wound treatments. Hydrogels, which are three-dimensional (3D) polymer networks cross-linked through physical interactions or covalent bonds, are promising for topical antibacterial applications because of their excellent adhesion, antibacterial properties, and biocompatibility. To further improve the healing performance of hydrogels, various modification methods have been developed with superior biocompatibility, antibacterial activity, mechanical properties, and wound repair capabilities. This review summarizes hundreds of typical studies on various ingredients, preparation methods, antibacterial mechanisms, and internal antibacterial factors to understand adhesive hydrogels with natural antibacterial agents for wound dressings. Additionally, we provide prospects for adhesive and antibacterial hydrogels in biomedical applications and clinical research.

Evaluating the adhesive potential of the newly isolated bacterial strains in research exploitation of plant microbial interaction

Bacterial adhesion potential constitutes the transition of bacteria from the planktonic to the static phase by promoting biofilm formation, which plays a significant role in plant-microbial interaction in the agriculture industry. In present study, the adhesion potential of five soil-borne bacterial strains belonging to different genera was studied. All bacterial strains were capable of forming colonies and biofilms of different levels of firmness on polystyrene. Significant variation was observed in hydrophobicity and motility assays. Among the five bacterial strains (SH-6, SH-8, SH-9, SH-10, and SH-19), SH-19 had a strong hydrophobic force, while SH-10 showed the most hydrophilic property. SH-6 showed great variability in motility; SH-8 had a swimming diffusion diameter of 70 mm, which was three times higher than that of SH-19. In the motility assay, SH-9 and SH-10 showed diffusion diameters of approximately 22 mm and 55 mm, respectively. Furthermore, among the five strains, four are predominately electron donors and one is electron acceptors. Overall, positive correlation was observed among Lewis acid base properties, hydrophobicity, and biofilm forming ability. However, no correlation of motility with bacterial adhesion could be found in present experimental work. Scanning electron microscopy images confirmed the adhesion potential and biofilm ability within extra polymeric substances. Research on the role of adhesion in biofilm formation of bacteria isolated from plants is potentially conducive for developing strategies such as plant-microbial interaction to mitigate the abiotic stress.

A universal coating strategy for inhibiting the growth of bacteria on materials surfaces

The development of a versatile antibacterial coating, irrespective of material characteristics, is greatly attractive but still a challenge. In this work, mussel-inspired dopamine-modified sodium alginate (SA-DA) was successfully synthesized as the adhesion layer, and antibacterial coatings on three types of substrates, namely cotton fabric, aluminum sheet, and polyurethane membrane, were constructed through the layer-by-layer (LbL) deposition of polyhexamethylene guanidine and sodium alginate. Among the coated materials, the coated cotton fabric was systematically characterized, and the results showed that it still exhibited ideal hydrophilicity, and its liquid absorption capacity increased with an increase in the coating layers. The growth of Escherichia coli and Staphylococcus aureus was notably inhibited on the coated cotton fabric, and 10 coating bilayers achieved 100% inhibition of bacterial growth within 10 min. Furthermore, an ideal antibacterial ability maintained after 10 cycles of antibacterial trials or 50 washing or soaping cycles. In vitro evaluation of the hemostatic effect indicated that the coated cotton fabric could promote blood clotting by concentrating the components of blood and activating the platelets, and no significant hemolysis and cytotoxicity were observed in the coated cotton fabric. Moreover, the coated aluminum and polyurethane film also displayed an obvious antibacterial effect, which proved that the constructed coating could successfully adhere to the metal and polymer surfaces. Therefore, this work provided a proper way for the progress of a current antibacterial coating tactics for different substrate surfaces.