Search Results (217)

This work introduces an original sequential bio-inspired strategy combining lytic phage pretreatment with TiO₂–thyme essential oil (TEO) photocatalysis, achieving near-complete inhibition of both biofilm initiation and maturation. By simultaneously targeting planktonic cells, mature biofilms, and extracellular DNA (eDNA), this approach addresses key mechanisms involved in biofilm persistence. Pseudomonas aeruginosa ATCC 4114 was selected as the biological model due to its relevance in water distribution systems and its strong biofilm-forming ability. Experimental results showed that phage pretreatment alone inhibited biofilm formation by planktonic cells by up to 99.6% (inactivation rate constant k = 0.034 min⁻¹) and weakened bacterial attachment in mature biofilms by 89.06% (k = 0.011 min⁻¹). To further enhance photocatalytic efficacy, titanium dioxide (TiO₂) was combined with TEO at 0.05% (v/v) as a bio-inspired photosensitizer. UV–Vis spectroscopy confirmed TiO₂-TEO interactions that extended light absorption into the visible region (400–700 nm), thereby enhancing photocatalytic efficiency. This combination was designed to suppress residual biofilm development and disrupt extracellular DNA (eDNA), a critical component of biofilm structure and stability. The integrated approach involving phage pretreatment followed by TiO₂–TEO (0.05%) photocatalysis achieved 99.99% inhibition of both biofilm initiation and maturation phases, with significantly increased kinetic parameters (A = 2.62 for planktonic cells and A = 3.65 for sessile cells; k = 0.076 min⁻¹ and 0.063 min⁻¹, respectively; p < 0.01). This study provides novel insights into water disinfection strategies using photocatalytic treatment, emphasizing the importance of monitoring post-treatment bacterial virulence factor expression. Full article

Candida albicans, a commensal and opportunistic fungal pathogen, is a major clinical concern due to its ability to cause infections ranging from mild mucosal conditions to life-threatening systemic diseases, particularly in immunocompromised patients. Its capacity to form biofilms on medical devices further complicates treatment by enhancing antifungal resistance and immune evasion. In the search for novel therapeutic strategies, the lysine-enriched amphibian-derived temporin B analog, TB_KKG6K, has emerged as a promising antifungal agent. This study demonstrates that TB_KKG6K exhibits potent fungicidal activity against planktonic C. albicans cells, with a low potential to induce adaptation or resistance. TB_KKG6K has no adverse impact on the anti-Candida efficacy of standard antifungal drugs when applied in combination, interacting additively with amphotericin B and caspofungin in a fungicidal mode of action. Additionally, TB_KKG6K effectively reduces biofilm maturation on silicone elastomers, a material commonly used in medical devices, further highlighting its therapeutic potential. These data together with our previous documentation of minimal cytotoxicity and irritation potential in human cells makes TB_KKG6K a strong candidate for combating both planktonic and biofilm-associated C. albicans infections. These findings underscore the dual efficacy of TB_KKG6K and its potential to address the challenges posed by C. albicans in clinical settings. Full article

Managing bacterial infections and the spread of microbial resistance is one of the most critical and complex tasks of modern healthcare infrastructures. Antiseptics and disinfectants such as biocides play a significant role in controlling microbial resistance by reducing the microbial load on surfaces, skin, and environments, thereby limiting the opportunity for pathogens to proliferate and develop resistance. Herein, we tested the different interactions of quaternary ammonium compound (QAC)-based biocide compositions in pursuit of a better antimicrobial performance. An extensive microbiological analysis was conducted for 12 selected compositions of various combinations of mono-QACs, bis-QACs, and alcohols on 17 strains of bacteria of the ESKAPEE group and fungi, including 11 clinical highly resistant varieties, highlighting synergistic or additive dynamics. The evaluation showed noticeable improvements in activity, with up to 16-fold MBC and 32-fold MBEC reductions for alcohol-based compositions of lead QAC. Moreover, synergistic interactions were detected and confirmed via an optimized checkerboard assay for pyridinium QAC combinations against planktonic Gram-positive S. aureus with a fractional inhibitory concentration index (FICI) and fractional bactericidal concentration index (FBCI) of 0.39–0.5 and Gram-negative A. baumannii biofilms. The studied biocides demonstrated the long-term preservation of antimicrobial efficiency without resistance development during a 40-day period and do not induce QAC-associated cross-resistance for four commercially available antibiotics with similar mechanisms of action. Full article

Chronic infections pose significant clinical challenges due to their persistent nature, heightened resistance to conventional therapies, and association with biofilm formation. Neutrophil extracellular traps (NETs), released through a unique form of cell death known as NETosis, serve as an innate immune defense mechanism by trapping and neutralizing pathogens. However, accumulating evidence reveals a complex and paradoxical relationship between NETs and microbial biofilms. While NETs can immobilize and kill planktonic microbes, the extracellular DNA and associated proteins often contribute to biofilm stability, immune evasion, and chronic infection persistence. This review explores the bidirectional interactions between NETosis and biofilm formation, with a focus on their synergistic roles in the pathogenesis of chronic infections such as cystic fibrosis lung disease, diabetic foot ulcers, periodontitis, and implant-associated infections. We outline the molecular mechanisms governing NETosis, the structural and functional dynamics of biofilms, and how these processes intersect to form recalcitrant infection niches. Emerging therapeutic strategies aimed at disrupting this pathogenic interplay including DNase-based treatments, PAD4 inhibitors, and combination therapies are critically evaluated. By illuminating the pathogenic synergy between NETs and biofilms, this review underscores the need for integrated immunomodulatory and anti-biofilm interventions to effectively manage chronic infectious diseases and improve patient outcomes. Full article

Background: Rapidly growing mycobacteria (RGM) are microorganisms with variable pathogenicity, which can cause different clinical forms of mycobacterioses. They can form structured communities at the liquid-air interface and adhere to animate and inanimate solid surfaces, characterizing one of their most powerful mechanisms of resistance and survival, named biofilms. Objectives: Here, a novel series of sulfamethoxazole (SMTZ) Schiff bases were obtained by the condensation of the primary amine from SMTZ core with six different aldehydes to evaluate their antimicrobial and antibiofilm activities, as well as physicochemical and in silico characteristics. Methods: The compounds L1–L6 included: pyridoxal hydrochloride (L1), salicylaldehyde (L2), 3-methoxysalicylaldehyde (L3), 2-hydroxy-1-naphthaldehyde (L4), 3-allylsalicylaldehyde (L5), and 4-(diethylamino)salicylaldehyde (L6). MIC determination was performed against standard strains and seven clinical isolates. Time-kill assays, biofilm inhibition assays, atomic force microscopy, and peripheral blood mononuclear cell cytotoxicity assays were carried out. Density functional theory (DFT) calculations using quantum descriptors, Mulliken charges, Fukui functions, non-covalent interactions (NCI), and reduced density gradient (RDG), along with molecular docking calculations to DHS, LasR, and PqsR, supported the experimental trend. Results: The compounds L1–L6 showed a significant capacity to inhibit the growth of RGM, with MIC values in the range of 0.61 to 1.22 μg mL⁻¹, which are significantly lower than those observed for the parent compound SMTZ, demonstrating superior antimicrobial potency. To deepen antimicrobial activity assays, L1 was chosen for further evaluations and showed a significant ability to inhibit the growth of RGM in both planktonic and biofilm forms. In addition, atomic force microscopy views great changes in topography, electrical force, and nanomechanical properties of microorganisms. The cytotoxic assays with the peripheral blood mononuclear cell model suggest that the new compound may be considered as an antimicrobial alternative, as well as a safe substance showing selectivity indexes in the range of efficacy. Conclusions: Density functional theory (DFT) calculations were performed to obtain quantum descriptors, Mulliken charges, Fukui functions, non-covalent interactions (NCI), and reduced density gradient (RDG), which, with molecular docking calculations to DHS, LasR, and PqsR, supported the experimental trend. Full article

Reservoirs are hotspots for the coupling of nutrients and heavy metals, and they substantially modify the compositions and spatiotemporal distributions of microorganisms in fluvial systems. However, relatively few studies have been performed that investigate the microbial mechanisms driving interactions among heavy metals and nutrients in reservoirs. The Goupitan Reservoir, a seasonal stratified reservoir located within the Wujiang River catchment, was chosen as the research subject. The temporal and spatial variations in heavy metals and nutrients, and the metagenomic composition of the reservoir water were analyzed in January, April, July, and October 2019. The results revealed that As, Ni, Co, and Mn were derived primarily from mine wastewater, whereas Zn, Pb, Cd, and Cr were related to domestic and agricultural wastewater discharge. The study area was dominated by Proteobacteria, Actinobacteria, Cyanobacteria, and Bacteroidetes, with the proportion of dominant phyla reaching 90%. Decreases in the dissolved oxygen (DO) concentration and pH in the bottom water during July and October were conducive to increases in the abundance of the anaerobic bacterial groups Planctomycetes and Acidobacteria. The functional genes norBC and nosZ associated with denitrification (DNF), the key gene nrfAH involved in the dissimilatory nitrate reduction to ammonium (DNRA) process, the functional genes aprAB and dsrAB responsible for sulfate reduction/sulfide oxidation, as well as the thiosulfate oxidation complex enzyme system SOX, all exhibit high abundance in hypoxic water bodies and peak in the redoxcline, highlighting the significance of related nitrogen (N) and sulfur (S) metabolic processes. In addition, the concentrations of heavy metals significantly affected the spatial differentiation of the planktonic bacterial community structure, with Mn, Co, Fe, Ni, As, and Cu making relatively high individual contributions (p < 0.01). This study is important for elucidating the sources and microbiological mechanisms influencing heavy metals and nutrients in seasonally stratified subtropical reservoirs. Full article

Background: Gram-positive bacteria, once considered incapable of producing extracellular vesicles (EVs) due to their thick peptidoglycan layer, are now known to secrete EVs that transport virulence factors and modulate host immunity. These EVs contribute to bacterial pathogenicity by facilitating biofilm formation, immune evasion, and inflammation. Granulicatella adiacens, an oral commensal associated with infective endocarditis, represents a clinically relevant model to study EV-mediated virulence. Objectives: This study’s aim was to investigate whether the proteomic composition and immunomodulatory activity of G. adiacens EVs differ between biofilm and planktonic lifestyles, thereby contributing to distinct pathogenic behaviours. Methods: EVs isolated from G. adiacens CCUG 27809 cultures were characterized using nano LC-ESI-MS/MS, followed by comprehensive bioinformatic and cytokine assays. Results: Quantitative proteomic profiling identified 1017 proteins, revealing distinct signatures between biofilm- and planktonic-derived EVs. Principal component analysis showed clear segregation between the two states, with biofilm EVs enriched in proteins linked to stress adaptation, adhesion, and structural integrity, while planktonic EVs exhibited growth- and metabolism-related proteins. A total of 114 virulence-associated proteins were identified, including several novel candidates. Functionally, EVs from both conditions significantly induced pro-inflammatory cytokines IL-8 and IL-1β in a dose-dependent manner (p < 0.05), whereas IL-17 remained unchanged. Conclusions: G. adiacens EVs exhibit lifestyle-dependent proteomic and immunomodulatory differences, underscoring their role in host–pathogen interactions and endocardial infection. These findings provide a foundation for future mechanistic and in vivo studies exploring EV-mediated virulence and potential therapeutic modulation. Full article

In freshwater ecosystems, cross-trophic interactions among biological communities underpin ecosystem stability and functionality. In arid and semi-arid rivers, however, hydrological fluctuations, invasive species, and other perturbations exacerbate the complexity of biological processes. To systematically assess the community structure of fish, eukaryotic plankton, and prokaryotic microorganism in the Irtysh River basin, this study employed environmental DNA (eDNA) metabarcoding for monitoring. High-throughput sequencing of taxa within the study area was conducted via eDNA metabarcoding, coupled with random forest and linear mixed models to dissect the effects of community structure. The eDNA approach effectively unraveled spatial patterns of biodiversity and identified taxon-specific diversity hotspots: invasive fish exerted a facilitative effect on algae and suppressed the richness of protozoa, fungi, and heterotrophic microorganisms, yet had minimal impact on the dominant structure of autotrophic microorganisms. These findings provide a scientific basis for basin-scale ecological management, emphasizing the necessity of balancing habitat preservation and invasive-species control to safeguard ecosystem functionality. Full article

Background: Oral infections such as dental caries and candidiasis are mediated by resilient biofilms, which are increasingly tolerant to conventional antimicrobials. This study investigated the antimicrobial and antibiofilm effects of Salvia officinalis and Nigella sativa CO₂ extracts against Streptococcus mutans and Candida albicans, with emphasis on synergistic interactions. Methods: Extracts were analyzed using gas chromatography–mass spectrometry analysis (GC–MS) and evaluated through planktonic MIC/MBC assays, time–kill kinetics, and biofilm models (MBIC/MBEC, biomass, metabolic activity). A novel three-dimensional checkerboard (3D-CB) and fractional inhibitory concentration index (FICI) approach was applied to optimize extract ratios, concentrations, and exposure times. Results: S. officinalis extract showed greater activity against S. mutans (MIC 256 mg/L; MBC 512 mg/L), while N. sativa was more effective against C. albicans (MIC 256 mg/L; MFC 512 mg/L). Both extracts reduced biofilm biomass and metabolic activity by over 70% at higher doses. Synergy was confirmed at ratios of 70:30 (S. officinalis: N. sativa) for S. mutans (FICI 0.38) and 40:60 for C. albicans (FICI 0.42). The achieved synergistic effect further decreased MBEC values fourfold and prolonged post-antibiotic effects. Conclusions: Synergistic S. officinalis–N. sativa formulations enhanced antimicrobial activity against oral pathogens in both planktonic and biofilm states, supporting their potential as next-generation dental antimicrobials. Full article

Enterohemorrhagic Escherichia coli (EHEC) forms persistent biofilms on meat processing surfaces, posing a significant cross-contamination risk. This study assessed the antagonistic capacity of lactic acid bacteria (LAB) against EHEC under meat-processing-like conditions. Three LAB strains were tested in planktonic co-culture with EHEC at 12 °C, all displaying bactericidal activity. In biofilm assays on stainless steel, LAB reduced EHEC biofilms without affecting their own viability. LAB cell-free supernatants further inhibited EHEC biofilms by 2.6–3.5 log CFU/cm², highlighting the role of secreted antagonistic compounds. Among the tested strains, Pediococcus pentosaceus CRL 2145 showed the strongest effect and was selected for deeper analysis. Fluorescence microscopy confirmed EHEC cell death within mixed biofilms. Proteomic profiling of CRL 2145 under mixed-biofilm conditions revealed 162 differentially expressed proteins, with 156 upregulated. These proteins were mainly associated with metabolism, transcription, translation, and stress response pathways, suggesting a multifactorial inhibitory mechanism involving metabolic dominance, physical competition, and secretion of antagonistic molecules. Overall, this study deepens our understanding of the molecular and physiological aspects of LAB–EHEC interaction. P. pentosaceus CRL 2145 emerges as a promising biocontrol agent that could be applied, alone or with its supernatants, to meat processing surfaces to improve food safety. Proteomic data: ProteomeXchange PXD067300. Full article

Uropathogenic Escherichia coli (UPEC) is a primary cause of urinary tract infections (UTIs), with recurrent cases often linked to its ability to form biofilms. This study investigated the effects of various antibiotics on UPEC biofilm formation and the subsequent interaction of these biofilms/their supernatants with human neutrophils. We determined the minimum inhibitory concentrations (MIC), minimum bactericidal concentrations (MBC), and biofilm eradication concentrations (MBEC) for ampicillin, gentamicin, chloramphenicol, ciprofloxacin, and levofloxacin. Our results showed an increase in MBEC compared to MBC for all tested antibiotics, confirming the enhanced antibiotic resistance of bacteria in biofilm. We found that sub-MICs of ciprofloxacin, which moderately inhibited planktonic growth, actually stimulated an increase in biofilm biomass. This antibiotic-induced biofilm growth was accompanied by changes in bacterial morphology, including the formation of elongated, filamentous cells, an adaptive stress response. Biofilm-embedded bacteria, but not their supernatants, significantly reduced neutrophil viability, primarily by inducing neutrophil necrosis. The presence of ciprofloxacin during biofilm formation did not fundamentally alter interactions with neutrophils. These findings highlight the importance of studying effects of antibiotic pressure on biofilm formation, underscoring the challenges in antibiotic treatment of UTIs. Full article

Different sampling techniques were evaluated to assess potential differences in species richness and the abundances of phytoplankton across several lowland aquatic environments. Five sampling methods were used, including a bucket, narrow- and wide-mouth bottles, a 10 µm plankton net, and a vertical Van Dorn bottle. These sampling methods were applied in subtropical streams, shallow lakes, and rivers. The results were compared using a two-way ANOVA to evaluate differences in total density by considering the morphological group and major phytoplankton phyla. Similarity analyses (SIMPER) and a permutational multivariate analysis of variance (PERMANOVA) were performed to compare the relative abundances of the species. The results showed, in general (except with Cyanophyta, Chrysophyta, and colonies—coenobia), significant differences in the effect of the sampling method but without interaction with the kind of environment. Particularly, the plankton net always reported lower density estimations, with the bucket having the highest values and the wide–narrow bottle methods having similar values. SIMPER and PERMANOVA indicated differences, especially with the plankton net and the other methods, particularly the bucket. These findings suggest that the sampling method can influence species counts and registration in subtropical water ecosystems, highlighting the need for standardized procedures across countries to obtain comparable and reliable results. Full article

High doses of the antibiotic azithromycin in freshwater environments can impact planktonic organisms at both the individual and community levels, influencing interactions at the base of the food web. This study investigated the effects of azithromycin on the natural rotifer community feeding on phytoplankton from a eutrophic water body and its potential impacts on rotifer fitness (impaired mastax movement: slow, irregular or reduced frequency), grazing and mortality following acute exposure. The natural plankton community was exposed to three azithromycin concentrations based on the EC₅₀ value (EC₅₀, 1/2 EC₅₀ and 1/3 EC₅₀) and assessed at different exposure times (24, 48 and 72 h) in the microcosm experiments. The results showed that all azithromycin concentrations reduced the fitness of the rotifers, as indicated by impaired mastax movement and/or slow, irregular or reduced movement frequency. Impairment of mastax movement altered rotifer grazing and the abundance of phytoplankton. The rotifers in the control group suppressed abundant phytoplankton growth, suggesting that azithromycin impairs interspecific interactions between plankton species. Rotifer mortality occurred at 48 h after azithromycin exposure in all treated samples. These findings show that the effects of azithromycin can be observed at different trophic levels, affecting both phytoplankton and zooplankton through altered biotic interactions and suppressed grazing. Full article

Pseudomonas aeruginosa, a member of the “ESKAPE” group of bacterial pathogens, exhibits biofilm-forming capacity, a key factor contributing to its resistance to conventional antibiotics and posing significant challenges in clinical treatment. To develop more effective therapeutics against such infections, identifying potential drug targets through bioinformatics analysis is essential. Consequently, we utilized data from the GEO database to investigate differentially expressed genes between planktonic and biofilm groups, and identified drug targets through the construction of a protein–protein interaction (PPI) network and the cytoHubba algorithm. Inhibitors targeting this protein were identified through molecular docking screening of the FDA-approved drug library, and their anti-biofilm activity was validated in vitro. Through bioinformatics analysis, we identified GacS as the drug target in this study for treating biofilm-related infections. Virtual screening revealed that oxidized glutathione (GSSG) and arformoterol tartrate (ARF) are both capable of tightly binding to GacS and demonstrating good stability. In vitro experiments further confirmed that both GSSG and ARF demonstrated anti-biofilm activity, particularly when combined with azithromycin (AZM) or clarithromycin (CAM), significantly enhancing the biofilm inhibition effects of these antibiotics. This combination therapy offers a new and innovative strategy to combat biofilm-associated infections, showcasing the potential of GacS inhibitors in clinical applications. In conclusion, GSSG and ARF may serve as effective GacS inhibitors, and their combination with AZM or CAM could provide a novel approach for treating biofilm-related infections, paving the way for more effective treatment options. Full article

Predation plays a key organizational role in structuring plankton communities. However, predator diversity can lead to emergent effects in which the outcomes of predator–prey interactions are modified. The response of the plankton community to three different predator regimes at natural densities was investigated over a 10-day mesocosm experiment in a temperate, temporarily open/closed estuary in South Africa. The regimes included: (1) predation by the mysid, Mesopodopsis wooldridgei; (2) predation by larval Rhabdosargus holubi and (3) a combination of the two predators. M. wooldridgei are primarily copepod feeders, and juvenile R. holubi consume a broader diet including zooplankton, algae and invertebrate fauna. In the absence of predators, zooplankton grazing contributed to a significant decline in the phytoplankton size structure and total chlorophyll-a (Chl-a) concentration. The presence of the predators contributed to a decline in the total zooplankton abundances and biomass which dampened the grazing impact of the zooplankton on the total Chl-a, consistent with the expectations of a trophic cascade. There were no significant differences in the size structure of the phytoplankton community, total Chl-a concentration and the total zooplankton abundances and biomass between the different predator treatments, suggesting that the increase in predator diversity did not contribute to increased prey risk. These findings highlight both the direct and indirect ecological impacts of predators on plankton dynamics. Full article