Search Results (88)

Water systems are highly vulnerable to biofilm formation, which can compromise water quality, operational efficiency, and public health. Factors such as surface material properties and gravitational orientation of the surface play critical roles in the early stages of microbial attachment and biofilm development. This study examines the impact of gravity and surface composition on the initial adhesion of Pseudomonas fluorescens AR11—a model organism for biofilm research. Focusing on stainless steel (SS) and polycarbonate (PC), two materials commonly used in water and wastewater infrastructure, bacterial adhesion was evaluated at surface inclinations of 0°, 45°, 90°, and 180° to assess gravitational impact. After three hours of contact, fluorescence microscopy and image analysis were used to quantify surface coverage and cluster size distribution. The results showed that both material type and orientation significantly affected early biofilm formation. PC surfaces consistently exhibited higher bacterial adhesion at all angles, with modest variations, suggesting that material properties are a dominant factor in initial colonization. In contrast, SS showed angle-dependent variation, indicating a combined effect of gravitational convection and surface characteristics. These insights contribute to a deeper understanding of biofilm dynamics under realistic environmental conditions, including those encountered in space systems, and support the development of targeted strategies for biofilm control in water systems and spaceflight-related infrastructure. Full article

Background: Dental enamel demineralization is a critical early event in the development of dental caries. To address this, bioactive compounds have been explored for their potential to mitigate enamel demineralization and promote remineralization. Previous studies have demonstrated that varnishes containing natural compounds such as trans,trans-farnesol (tt-farnesol), quercetin, and theobromine exhibit antimicrobial activity, suggesting potential in caries prevention. Thus, this laboratory study assessed the ability of these varnishes to prevent enamel caries lesion formation by using a chemical model to determine whether these natural compounds interfered with de- and remineralization processes in the absence of a cariogenic biofilm. Methods: Sixty bovine enamel specimens, each measuring 5 × 5 × 2 mm, were selected according to their initial surface hardness (SHI), measured by Knoop hardness in three indentations spaced 100 µm apart. The specimens were allocated to the following groups in a random manner (n = 15): an experimental varnish without compounds (NC/negative control); experimental varnishes containing the combination of tt-farnesol, quercetin, and theobromine at concentrations of 1.5% (E1) and 4.5% (E2); and Duraphat™ (NaF 5%/gold standard—D). After applying the varnishes, they remained in artificial saliva for 6 h. The specimens were then subjected to 8 pH cycles, including 4 h of demineralization and 20 h of remineralization. Surface hardness was measured again to calculate the percentage of surface hardness loss (%SHL), and three specimens from each group were examined using scanning electron microscopy. Comparisons were made using ANOVA (p < 0.05). Results: The D group (5% NaF) demonstrated a significantly lower %SHL (75.5% ± 7.88) than the other groups (p < 0.05). E1 (86.3% ± 5.33) was statistically similar to NC (81.8% ± 4) but lower than E2. E2 showed the highest %SHL (91.6% ± 3.64) compared to the other groups. Surface demineralization was evident in all specimens post pH cycling. Conclusion: The bioactive varnishes containing tt-farnesol, quercetin, and theobromine at concentrations of 1.5% and 4.5% did not exhibit a protective effect against mineral loss in dental enamel in the absence of a cariogenic biofilm. Full article

Furfural is a relevant industrial product, but its presence in water and soil generates contamination and health risks. Moving bed biofilm reactors (MBBRs) are an increasingly used alternative to eliminate contaminants with the advantage of occupying small spaces, despite their high dependence on support and the microorganisms involved in the process. This work proposes furfural elimination through a laboratory-scale MBBR using Bacillus licheniformis GTQ1, Microbacterium sp. GISTAQ2, and Brevundimonas sp. GISTAQ1 isolated from an industrial effluent and agroforestry waste (rice husks, pine sawdust, and quebracho chips) as supports. The biofilm development was tested with both axenic and mixed cultures, confirming high coverage by Scanning Electron Microscope (SEM) images, especially in triple-mixed cultures. Biodegradation tests were carried out in the MBBR with 15 g rice husks or quebracho chips as supports and a 4000 mg L⁻¹ initial furfural concentration for 72 h. The mixed culture achieved almost a 100% furfural removal in three days with a rate of 3.97% per hour with rice husks and 2.61% per hour with quebracho chips. This laboratory-scale MBBR development is a promising first step ready for a scale-up for its implementation in industries to significantly reduce the environmental impact of the discharge of this type of effluent. Full article

Objectives: The synergistic effect of shock wave-enhanced emission photoacoustic streaming (SWEEPS) and antimicrobial photodynamic therapy (aPDT) in mandibular molar root canal disinfection remains underexplored, particularly against dual-species biofilms that better simulate clinical conditions. This study evaluates their combined antimicrobial efficacy against Enterococcus faecalis and Candida albicans biofilms and assesses potential tooth discoloration caused by riboflavin and nano-curcumin. Materials and Methods: The mesiobuccal canals of 57 extracted mandibular molars were inoculated with E. faecalis and C. albicans biofilms. The antimicrobial effects were assessed using riboflavin or nano-curcumin with a 450 nm diode laser (BDL), SWEEPS, or their combinations, compared to 5.25% NaOCl (positive control) and saline (negative control). Biofilm reduction was quantified by colony-forming units (CFUs/mL), and discoloration was evaluated using the ΔE metric in the CIE L*a*b* color space. Results: Both microorganisms showed a significant decrease in colony numbers in all experimental groups compared to the negative control (p < 0.001), except for E. faecalis, where no significant difference was observed between the riboflavin/nano-curcumin groups and the negative control. Combining riboflavin or nano-curcumin with SWEEPS or BDL significantly enhanced antimicrobial efficacy compared to individual treatments (p < 0.001). The combined photodynamic therapy and SWEEPS groups showed the lowest colony counts. The ΔE values were, on average, 1.81 for riboflavin and 1.09 for nano-curcumin. Conclusions: The combination of SWEEPS and aPDT effectively reduces E. faecalis and C. albicans biofilms in molars, supporting its potential as an adjunct in endodontic disinfection. Minimal discoloration further highlights its clinical applicability. Full article

In this study, we explore the use of C. kluyveri in synthetic biofilms for the production of 1-butyrate and 1-hexanoate, investigating the impact of inoculation temperature during biofilm formation and the presence of yeast extract. Therefore, a novel synthetic biofilm reactor has been designed and constructed. Prior to investigating synthetic biofilms in this reactor, we carried out preliminary batch experiments in anaerobic flasks containing an inoculated agar hydrogel fixed at the bottom and overlaid medium. For the operation of the novel synthetic biofilm reactor, specific volumes of inoculated agar hydrogel were dispensed into a cylindrical mold with a diameter of 102 mm, forming the synthetic biofilm with a height of 4 mm, which was then transferred into the biofilm reaction chamber onto the support grid. The biofilm support grid separates the gas phase (CO₂, N₂) above the synthetic biofilm from the aqueous phase (medium) below. Our results show that C. kluyveri remains metabolically active at biofilm preparation temperatures of up to 45 °C, with extended lag phases observed at 70 °C. The synthetic biofilm demonstrated efficient chain elongation in batch processes, converting ethanol and acetate into 1-butyrate and 1-hexanoate, with final concentrations of 2.7 g L⁻¹ and 10.1 g L⁻¹, respectively, with yeast extract in the circulating liquid medium of the synthetic biofilm reactor setup. The maximum estimated space-time yields for 1-butyrate and 1-hexanoate, referenced to the biofilm volume, were 1.331 g L⁻¹ h⁻¹ and 4.947 g L⁻¹ h⁻¹, respectively. Experiments without yeast extract lead to final concentrations of 2.0 g L⁻¹ 1-butyrate, and 7.3 g L⁻¹ 1-hexanoate and maximum estimated space-time yields, referenced to the biofilm volume, were 0.332 g L⁻¹ h⁻¹ and 1.123 g L⁻¹ h⁻¹, respectively. The use of synthetic biofilms, even without yeast extract, eliminates the need for significant cell growth during chain elongation. However, product concentrations were lower without yeast extract. Full article

Non-invasive phototherapy includes modalities such as photodynamic therapy (PDT) and photothermal therapy (PTT). When combined with tumor immunotherapy, these therapeutic approaches have demonstrated significant efficacy in treating advanced malignancies, thus attracting considerable attention from the scientific community. However, the progress of these therapies is hindered by inherent limitations and potential adverse effects. Recent findings indicate that certain therapeutic strategies, including phototherapy, can induce immunogenic cell death (ICD), thereby opening new avenues for the integration of phototherapy with tumor immunotherapy. Currently, the development of biofilm nanomaterial-encapsulated drug delivery systems has reached a mature stage. Immune cell membrane-encapsulated nano-photosensitizers hold great promise, as they can enhance the tumor immune microenvironment. Based on bioengineering technology, immune cell membranes can be designed according to the tumor immune microenvironment, thereby enhancing the targeting and immune properties of nano-photosensitizers. Additionally, the space provided by the immune cell membrane allows for the co-encapsulation of immunotherapeutic agents and chemotherapy drugs, achieving a synergistic therapeutic effect. At the same time, the timing of photodynamic therapy (PDT) can be precisely controlled to regulate the action timing of both immunotherapeutic and chemotherapy drugs. This article summarizes and analyzes current research based on the aforementioned advancements. Full article

The Biofilm Onboard Radiation Exposure Assessment Lab In Space (BOREALIS) mission is a 6U CubeSat initiative funded by the Italian Space Agency under the ALCOR program, executed through a collaboration among the School of Aerospace Engineering of Sapienza University of Rome, Interdepartmental Centre for Industrial Aerospace Research (CIRI Aerospace) of the University of Bologna and Kayser Italia Srl. BOREALIS is equipped with a lab-on-chip payload for studying the effects of microgravity and ionising radiation on microbial biofilms, which are crucial for understanding and preventing persistent infections in space environments. The satellite will operate across multiple orbits, moving from low to medium Earth orbit, to distinctly analyse the impacts of radiation separate from microgravity. The required orbital transfer not only tests the autonomy of its on-board systems in challenging conditions but also places BOREALIS among the first and few CubeSats to have ever attempted such a complex manoeuvre. This study explores the systematic application of Model-Based Systems Engineering to satellite design, from conceptualisation to trade-offs, using a tradespace analysis approach supported by Monte Carlo simulations to optimise mission configurations against performance and cost. Additionally, the adaptability of Model-Based Systems Engineering tools and the reusability of such an approach for other satellite projects are discussed, illustrating the BOREALIS mission as a case study for small mission design considering constraints and requirements. Full article

The accumulation of biofilms can potentially be very costly in terms of damage to mechanical systems and health impact on the human body. Space travel, especially long-term space travel, compounds the complications that arise from the accumulation of biofilms because of the lack of access to resources. This study investigates the ability of polyampholyte copolymer thin films to reduce bacteria adhesion in microgravity. Copolymer systems of [2-(acryloyloxy)ethyl] trimethylammonium chloride (TMA) and 2-carboxyethyl acrylate (CAA) and TMA and 3-sulfopropyl methacrylate potassium salt (SA) have previously shown resistance to bacteria adhesion under gravity-impacted conditions. However, their performance under microgravity conditions has never been evaluated. A self-contained payload was designed around multiple constraints to evaluate the ability of the TMA/CAA and TMA/SA thin film coatings to reduce the adhesion and biofilm formation of Staphylococcus epidermidis on aluminum test coupons in microgravity in an experiment conducted onboard the International Space Station (ISS). An Earth-based, gravity-impacted study was completed in parallel with the ISS experiment. The samples were then analyzed on the macroscale using photography and the microscale using confocal microscopy imaging to determine biofilm formation and bacteria attachment, respectively. The percentage of each sample covered by bacteria and/or biofilm was characterized and compared amongst the coating types and gravity exposure conditions. The TMA/SA coatings showed the lowest levels of bacteria adhesion and biofilm formation overall. The TMA/CAA coatings showed the largest reduction in bacteria adhesion and biofilm formation when comparing adhesion between the microgravity- and gravity-impacted samples. Therefore, both the copolymers demonstrate promise for bacteria-resistant coatings in microgravity. Full article

We derive a one-dimensional macroscopic model for biofilm formation in a porous medium reactor to investigate the role of longitudinal diffusion of substrate and suspended bacteria on reactor performance. By comparing an existing base model—one without longitudinal diffusion, which was the point of departure for our work, to the new model—we noticed significant changes in system dynamics. Our results suggest that neglecting it can lead to underestimation of quenching length and biofilm accumulation downstream, even in the advection-dominated regime. The effects of attachment and detachment of suspended bacteria on biofilm formation and substrate degradation were also examined. In the one-dimensional model, it was found that attachment has a stronger influence on substrate depletion, which becomes more pronounced as diffusion in the pore space increases. Full article

Periodontal patients may face orthodontic problems because of bone support loss, such as maxillary incisor proclination, spacing, rotation, extrusion, pathologic tooth migration (PTM) or traumatic occlusion. Orthodontic treatment is therefore an element within the comprehensive treatment of periodontitis after the periodontal condition has stabilized. The presence of fixed appliances (FAs) promotes the accumulation of bacterial biofilm and impedes hygiene procedures. The increasing popularity of clear aligner (CA) treatment is due to the convenience of use, less discomfort, better esthetics, easier hygiene, lower failure rate, and shorter, less frequent visits. Therefore, the question arises whether treatment with aligners is a good solution for periodontal patients. To answer this question, the PubMed/Medline, Cochrane Library and EMBASE databases were searched using the following keywords: periodontitis, orthodontic treatment, clear aligners, multibracket orthodontic appliances, fixed appliance, root resorption, gingival recession and pathologic tooth migration. The search strategy identified 18 relevant studies. A total of 1090 participants took part in the analyzed studies. The available literature was analyzed in terms of the occurrence of root apex resorption, the possibility of treating pathologic tooth migration, the occurrence of gingival recession, periodontal health status and occlusal stability in patients treated with CAs and FAs. Despite statistically significant differences in terms of Plaque Index (PI), probing depth (PD), apical root resorption and gingival recession favor the use of CAs. However, these values are mostly of no clinical significance. It is possible to treat PTM with CAs, but it is limited by the high degree of tooth mobility and incisor inclination. Obtaining perfect occlusion is comparably difficult in both CA and FA treatment. When planning orthodontic treatment in patients with reduced periodontium, the use of both CAs and FAs should be considered. The choice of method would ultimately depend on the patient’s dental condition. Full article

Plant food production generates a lot of by-products (BPs). These BPs are majorly discarded into the environment, polluting it, or into landfills where they just decompose, providing no benefit and taking up storage space, causing financial costs. These plant BPs are biodegradable, but reusing them may provide a better outcome and profit. The vast majority of plant-based food BPs are polysaccharide polymers like gums, lignin, cellulose, and their derivatives. It is possible to utilize plant food production waste, like banana peels, leaves, pseudostems, and inflorescences, to produce bioethanol, single-cell protein, cellulase, citric acid, lactic acid, amylase, cosmetics, fodder additives, fertilizers, biodegradable fibers, sanitary pads, bio-films, pulp and paper, natural fiber-based composites, bio-sorbents, bio-plastic, and bio-electricity in the agro-industry, pharmaceutical, bio-medical, and bio-engineering fields. Moreover, the use of banana BPs seems to be a way of dealing with many issues in underdeveloped countries, providing a clean and ecological solution. The suggested idea might not only reduce the use of plastic but also mitigate waste pollution. Full article

Background: Periodontitis preceded by gingivitis is the most common form of periodontal disease and occurs due to the interaction of microorganisms present in the complex bacterial aggregates of dental plaque biofilm and their metabolism products with periodontal tissues. Histamine is a heterocyclic biogenic amine acting via four types of receptors. Histamine H₃ receptors act as presynaptic auto/heteroreceptors to regulate the release of histamine and other neurotransmitters. Aim: Since the nervous system is able to regulate the progression of the inflammatory process and bone metabolism, the aim of this study was to investigate the effects of DL76, which acts as an antagonist/inverse agonist of H₃ receptors, on the course of experimental periodontitis. Materials and methods: This study was conducted in 24 mature male Wistar rats weighing 245–360 g, aged 6–8 weeks. A silk ligature was placed on the second maxillary molar of the right maxilla under general anesthesia. From the day of ligating, DL76 and 0.9% NaCl solutions were administered subcutaneously for 28 days in the experimental and control groups, respectively. After the experiment, histopathological, immunohistochemical and radiological examinations were performed. Results: Ligation led to the development of the inflammatory process with lymphocytic infiltration, increased epithelial RANKL and OPG expression as well as bone resorption. DL76 evoked a reduction in (1) lymphocytic infiltration, (2) RANKL and OPG expression as well as (3) bone resorption since the medians of the mesial and distal interdental spaces in the molars with induced periodontitis were 3.56-fold and 10-fold lower compared to the corresponding values in saline-treated animals with periodontitis. Conclusion: DL76 is able to inhibit the progression of experimental periodontitis in rats, as demonstrated by a reduction in the inflammatory cell infiltration, a decrease in the RANKL/RANK OPG pathway expression and a reduction in the alveolar bone resorption. Full article

Bacterial growth and behavior have been studied in microgravity in the past, but little focus has been directed to cell size despite its impact on a myriad of processes, including biofilm formation, which is impactful regarding crew health. To interrogate this characteristic, supernatant aliquots of P. aeruginosa cultured on different materials and media on board the International Space Station (ISS) as part of the Space Biofilms Project were analyzed. For that experiment, P. aeruginosa was grown in microgravity—with matching Earth controls—in modified artificial urine medium (mAUMg-high Pi) or LB Lennox supplemented with KNO₃, and its formation of biofilms on six different materials was assessed. After one, two, and three days of incubation, the ISS crew terminated subsets of the experiment by fixation in paraformaldehyde, and aliquots of the supernatant were used for the planktonic cell size study presented here. The measurements were obtained post-flight through the use of phase contrast microscopy under oil immersion, a Moticam 10+ digital camera, and the FIJI image analysis program. Statistical comparisons were conducted to identify which treatments caused significant differences in cell dimensions using the Kruskal–Wallis and Dunn tests. There were statistically significant differences as a function of material present in the culture in both LBK and mAUMg-high Pi. Along with this, the data were also grouped by gravitational condition, media, and days of incubation. Comparison of planktonic cells cultured in microgravity showed reduced cell length (from 4% to 10% depending on the material) and diameter (from 1% to 10% depending on the material) with respect to their matching Earth controls, with the caveat that the cultures may have been at different points in their growth curve at a given time. In conclusion, smaller cells were observed on the cultures grown in microgravity, and cell size changed as a function of incubation time and the material upon which the culture grew. We describe these changes here and possible implications for human space travel in terms of crew health and potential applications. Full article

Since they are difficult and sometimes impossible to treat, infections sustained by multidrug-resistant (MDR) pathogens, emerging especially in nosocomial environments, are an increasing global public health concern, translating into high mortality and healthcare costs. In addition to having acquired intrinsic abilities to resist available antibiotic treatments, MDR bacteria can transmit genetic material encoding for resistance to non-mutated bacteria, thus strongly decreasing the number of available effective antibiotics. Moreover, several pathogens develop resistance by forming biofilms (BFs), a safe and antibiotic-resistant home for microorganisms. BFs are made of well-organized bacterial communities, encased and protected in a self-produced extracellular polymeric matrix, which impedes antibiotics’ ability to reach bacteria, thus causing them to lose efficacy. By adhering to living or abiotic surfaces in healthcare settings, especially in intensive care units where immunocompromised older patients with several comorbidities are hospitalized BFs cause the onset of difficult-to-eradicate infections. In this context, recent studies have demonstrated that quaternary ammonium compounds (QACs), acting as membrane disruptors and initially with a low tendency to develop resistance, have demonstrated anti-BF potentialities. However, a paucity of innovation in this space has driven the emergence of QAC resistance. More recently, quaternary phosphonium salts (QPSs), including tri-phenyl alkyl phosphonium derivatives, achievable by easy one-step reactions and well known as intermediates of the Wittig reaction, have shown promising anti-BF effects in vitro. Here, after an overview of pathogen resistance, BFs, and QACs, we have reviewed the QPSs developed and assayed to this end, so far. Finally, the synthetic strategies used to prepare QPSs have also been provided and discussed to spur the synthesis of novel compounds of this class. We think that the extension of the knowledge about these materials by this review could be a successful approach to finding effective weapons for treating chronic infections and device-associated diseases sustained by BF-producing MDR bacteria. Full article

Bacteria have existed on Earth for billions of years, exhibiting ubiquity and involvement in various biological activities. To ensure survival, bacteria usually release and secrete effector proteins to acquire nutrients and compete with other microorganisms for living space during long-term evolution. Consequently, bacteria have developed a range of secretion systems, which are complex macromolecular transport machines responsible for transporting proteins across the bacterial cell membranes. Among them, one particular secretion system that stands out from the rest is the type V secretion system (T5SS), known as the “autotransporter”. Bacterial activities mediated by T5SS include adherence to host cells or the extracellular matrix, invasion of host cells, immune evasion and serum resistance, contact-dependent growth inhibition, cytotoxicity, intracellular flow, protease activity, autoaggregation, and biofilm formation. In a bacterial body, it is not enough to rely on T5SS alone; in most cases, T5SS cooperates with other secretion systems to carry out bacterial life activities, but regardless of how good the relationship is, there is friction between the secretion systems. T5SS and T1SS/T2SS/T3SS/T6SS all play a synergistic role in the pathogenic processes of bacteria, such as nutrient acquisition, pathogenicity enhancement, and immune modulation, but T5SS indirectly inhibits the function of T4SS. This could be considered a love–hate relationship between secretion systems. This paper uses the systematic literature review methodology to review 117 journal articles published within the period from 1995 to 2024, which are all available from the PubMed, Web of Science, and Scopus databases and aim to elucidate the link between T5SS and other secretion systems, providing clues for future prevention and control of bacterial diseases. Full article