Biofouling最新文献

Polymicrobial biofilms of Staphylococcus aureus and Pseudomonas aeruginosa pose serious clinical challenges due to their persistence, metabolic adaptability, and antibiotic tolerance. The present study investigated the ability of these two bacteria to co-exist and form mixed-species biofilms and evaluated the antibiofilm potential of piperine, a plant-derived alkaloid from Piper nigrum. Co-existence of S. aureus and P. aeruginosa was confirmed by enumeration of colony-forming units, growth kinetics, cross-streaking, metabolic fingerprinting, Gini coefficient analysis, and antibiotic susceptibility. Sub-minimum inhibitory concentrations of piperine significantly inhibited mixed-species biofilm formation, as demonstrated by biochemical, microbiological and microscopic analysis. Piperine treatment led to noticeable reductions in biofilm biomass, exopolysaccharide content, total protein content, metabolic activity and extracellular DNA. Mechanistic investigations revealed that piperine impaired biofilm-forming determinants by reducing cellular co-aggregation and cell surface hydrophobicity, inducing intracellular reactive oxygen species (ROS) accumulation, and increasing membrane permeability. Significantly, piperine effectively disrupted pre-established mixed-species biofilms, and its antibiofilm efficacy was further validated in a catheter model, highlighting its relevance against device-associated infections. Collectively, these findings demonstrate that piperine inhibits and disintegrates S. aureus-P. aeruginosa biofilms through diverse mechanisms, positioning it as a promising phytochemical for managing biofilm-associated infections.

The development of offshore renewable energy (ORE) is accelerating to reach global decarbonisation objectives, but it faces technical and ecological challenges, including biofouling. This review synthesises current knowledge on biofouling colonising ORE structures, focusing on: 1) its technical impacts (increased hydrodynamic drag, corrosion, decreased component lifespan), and 2) its environmental impacts (modification of habitat, reef effect, non-native species dispersal). Special focus is given to floating systems, such as floating wind turbines, where biofouling significantly influences mooring lines and dynamic cables. Despite increasing interest in the field, many uncertainties remain, notably the lack of in situ offshore data, limited understanding of biofouling-structure interactions, and absence of standardised measurement protocols. The review discusses main knowledge gaps in offshore fouling dynamics and proposes future research perspectives to improve maintenance strategies and environmental management. Understanding these processes is essential for the long-term sustainability of ORE technologies and their integration into marine ecosystems.

The exploration of multispecies biofilms has provided significant insight into how bacteria interact in natural environments. However, crucial information is still lacking when the assumption that all the bacteria approach the substrate simultaneously during multispecies biofilm formation is challenged. The objective of this study was to analyse the multispecies biofilm formed by industrially relevant bacteria, including Pseudomonas fluorescens and Listeria monocytogenes, focusing on sequential colonisation under turbulent flow and static conditions. Under flow conditions, the attachment of Listeria on preformed Pseudomonas biofilm was significantly higher (p < 0.001) and reached its highest cell concentration (8.9 log CFU cm^-2) earlier (by 24 h) compared to control (sterile stainless-steel surfaces) and co-inoculated (with P. fluorescens) conditions. The conditioning of stainless-steel surfaces with freeze-dried and rehydrated exopolysaccharides (0-27.5 µg ml^-1) extracted from P. fluorescens did not affect L. monocytogenes attachment, indicating the importance of biofilm architecture. The cell concentration of P. fluorescens was not affected by either the flow rate or the colonisation order in a multispecies biofilm. Overall, the sequence of colonisation affects biofilm formation in multispecies biofilms under turbulent flow and is an important variable in studies of the community lifestyle of multispecies biofilms.

This study examines the effects of ascorbic, acetic, citric, and lactic acids on resistant S. aureus, assessing planktonic growth using minimal inhibitory (MIC) and bactericidal concentrations, and evaluating mature biofilms for viability, biomass, enzyme activity, membrane integrity and stress. We found the lowest antimicrobial potential for acetic acid, followed by ascorbic acid, citric acid and lactic acid. Treatment of mature biofilms showed a reduction of up to 3 log CFU mL^-1 for lactic acid, while other organic acids were less effective. Lactic acid was also the most effective in reducing biofilm biomass by up to 33%, indicating potential for combination with other antibacterial compounds. The crystal violet staining confirmed a reduction in biomass regarding the non-treated samples. Iodonitrotetrazolium chloride assay showed a decrease in metabolic activity, with the highest formazan reduction (88%) observed with acetic acid. Live/dead staining indicated increased cell death at higher concentrations (9 MIC), with lactic acid causing the most severe membrane damage. In addition, intracellular stress increased with acid concentration. These findings reveal not only differential biofilm-targeting effects among common organic acids but also highlight the translational potential of lactic and acetic acids as cost-effective strategies to control resistant S. aureus in clinical and industrial settings, providing a foundation for future therapeutic and preventive applications.

Burkholderia pseudomallei, the causative agent of melioidosis, presents high antimicrobial resistance, largely due to its biofilm-forming ability. Here, innovative lecithin/chitosan microparticles loaded with lemongrass (LEO) and geranium (GEO) essential oils (LEOLCN and GEOLCN) were developed and characterized as a novel strategy to combat B. pseudomallei. Microparticles were characterized and evaluated for their effects on planktonic growth and biofilm inhibition, as well as for potential synergistic interactions with antibiotics. Microparticles exhibited a spherical morphology, high encapsulation efficiency, and sustained release profiles, with up to 45% of EO released at pH 2.0 and 32% at pH 7.4 after 50 h. LEOLCN demonstrated MICs ranging from 64 to 128 µg ml^-1 for most strains, although some resistant isolates exhibited MICs of up to 2,048 µg ml^-1. At a concentration of 512 µg ml^-1, both LEOLCN and GEOLCN reduced biofilm biomass and metabolic activity by more than 50%. LEOLCN exhibited synergistic effects with conventional antibiotics, reducing ceftazidime MICs by 2- to 9-fold, suggesting its potential to enhance antibiotic therapy against resistant strains. Scanning electron microscopy confirmed biofilm disruption. Overall, the dual antimicrobial and antibiofilm action of these compounds introduces a promising and innovative in vitro platform to address the persistent challenge of B. pseudomallei infections and biofilm-associated resistance.

Copper-nickel 90/10 alloys are widely used in marine environments due to their resistance to corrosion and biofouling. However, the influence of macrofouling on localised corrosion remains poorly understood. This study examines the effect of simulated macrofouling-induced crevices on CuNi 90/10 corrosion using laser-cut plastic shims to replicate hard fouling geometries. Samples with crevice gaps of 50, 130 and 1,000 µm were exposed for 180 days at two Australian marine sites: temperate (Melbourne) and tropical (Cairns). Crevice corrosion was most severe in Melbourne, with the 130 µm gap showing the deepest attack. In Cairns, samples showed lower crevice corrosion despite heavier external fouling, suggesting that fouling composition and protective calcareous deposits may mitigate attack. Crevice interiors lacked Desulfobacterota and exhibited less diverse communities with greater inter-replicate variability at both sites than outside surfaces. These results highlight the combined influence of environment, crevice geometry, corrosion product films, and biofouling composition on crevice corrosion of CuNi 90/10.

Multidrug-resistant pathogenic bacteria, particularly Pseudomonas aeruginosa (P. aeruginosa), pose a significant threat to human health. Despite the huge persistence of antibiotics, there remains a lack of effective natural compounds capable of simultaneously disrupting quorum sensing (QS), biofilm formation, and virulence in this pathogen. This study aimed to investigate the inhibitory potential of myricetin against P. aeruginosa focusing on its ability to interfere with QS-regulated virulence traits. Antibacterial, antibiofilm, anti-QS, and virulence factor activities were evaluated using crystal violet biofilm formation and QS-regulated virulence factor inhibition assays (e.g. pyocyanin, rhamnolipid, protease, and exopolysaccharides). The minimum inhibitory concentration (MIC) required to inhibit visible bacterial growth was 0.97 mg/mL. Additionally, the minimum biofilm inhibitory concentration of 50 (MBIC₅₀) was recorded at the MIC value. Myricetin showed a significant inhibitory effect against biofilm formation by suppressing bacterial hydrophobicity, aggregation, and swarming motility. Furthermore, myricetin significantly reduced the production of pyocyanin, rhamnolipid, protease, and exopolysaccharides. The myricetin effectively impeded QS mechanisms as evidenced by a significant reduction in the production of acyl homoserine lactone and violacein pigment, both qualitatively and quantitatively. Gene expression analysis exhibited a significant downregulation of LasI/R and RhlI/R genes, further enhancing the myricetin role in QS inhibition. Collectively, these findings demonstrate that myricetin effectively interferes with QS-mediated virulence mechanisms in P. aeruginosa, supporting its potential as a promising lead compound for developing anti-virulence strategies.

Polymicrobial biofilms are frequently associated with chronic infections and are highly tolerant to antibiotic treatment. Given that β-lactam antibiotics are the most prescribed antibiotics worldwide, we investigated β-lactam resistance in dual-species biofilms formed by Pseudomonas aeruginosa PAO1 and methicillin-sensitive Staphylococcus aureus (MSSA). Compared to monocultures, MSSA exhibited reduced susceptibility to cephalexin, ampicillin, and cefazolin, while P. aeruginosa showed reduced susceptibility to cefazolin and nafcillin within dual-species biofilms. Using a set of P. aeruginosa mutants, we demonstrate that the PAO1 AmpC β-lactamase, the exopolysaccharides Psl and Pel, and the quorum sensing regulators LasR and RhlR each play significant roles in protecting MSSA from β-lactam treatment. Interestingly, co-cultures of MSSA with the ΔpslA pelF mutant strain increased the survival of ΔpslA pelF under β-lactam exposure. Overall, these findings advance our understanding of how interdependent bacterial interactions compensate for the loss of matrix components and thereby contribute to antimicrobial tolerance in polymicrobial biofilms.

Ship hull grooming, a form of proactive in-water cleaning, has been extensively researched in a warm, productive, subtropical Atlantic location using US Navy-approved commercial coatings. Less is known about how grooming performs on toughened fouling control coatings or the grooming frequencies required in locations with lower seawater temperatures and lower fouling intensities. The purpose of this study was to explore differences in proactive in-water cleaning schedules due to changes in location and coating types. This study compared the time-based frequency of in-water grooming of two commercial and two experimental fouling control coatings in Port Canaveral, Florida, and Monterey, California. The results demonstrated that a higher grooming frequency was required to maintain surfaces free of fouling at the warm-water Port Canaveral, FL site compared to the cooler-water site in Monterey, CA. They also showed that the type of fouling control coating will influence the grooming frequency.

Marine biofouling has been negatively affecting human sailing since ancient times. Traditional antifouling coatings, such as tributyl tin-based coatings, were banned globally in 2008 due to their inherent toxicity and severe threat to the marine environment. Developing environmentally friendly, long-term marine antifouling coatings remains a huge challenge for the maritime industry. Capsaicin is one of the natural product antifoulants (NPAs). Capsaicin is favored by researchers due to its good antifouling effect and low toxicity. This review provides insights into four methods of application of capsaicin in the field of antifouling: incorporation into coatings, encapsulation via microcapsules, synthesis and exploration of capsaicin derivatives and incorporation into membranes to enhance the antifouling properties of materials. This paper compares the experimental data of various applied methods in the hope of enlightening interested researchers.