Microbial community divergence and environmental responses across multi-phase landfill environments.

Serotype-specific and temperature-dependent biofilm formation in Salmonella: Limited impact of antimicrobial resistance or source

Biofilm formation is a critical virulence mechanism in pathogens such as Klebsiella pneumoniae, a Gram-negative, encapsulated bacterium that has emerged as a zoonotic threat capable of infecting both humans and animals. Its biofilm-forming ability is closely associated with catheter-related and urinary tract infections. Given its potential to cross species barriers and cause significant public health concern, elucidating the environmental cues and conserved molecular pathways driving biofilm formation is essential for developing cross-species prevention strategies. Here we found that K. pneumoniae exhibited significantly greater biofilm-forming efficiency in urine than in nutrient-rich medium under comparable biomass conditions. Transposon-insertion sequencing (Tn-seq) identified 19 fitness genes essential for optimal growth in urine, most involved in the de novo biosynthesis of amino acids, particularly arginine, methionine, and isoleucine. Urine represents an amino acid-starved (AAS) environment for K. pneumoniae, modulating c-di-GMP signaling to promote biofilm formation. Eight diguanylate cyclase (DGC, c-di-GMP synthesis) genes, four phosphodiesterase (PDE, c-di-GMP degradation) genes, and four DGC+PDE genes were significantly regulated in response to urine. Furthermore, transcriptomic analysis comparing K. pneumoniae grown in urine with that grown in M9 medium revealed significant activation of genes associated with exopolysaccharide (EPS) biosynthesis, including those encoding lipopolysaccharides (LPS), capsules, peptidoglycan, and enterobacterial common antigen (ECA). Notably, K. pneumoniae increases EPS biosynthesis under the iron-limited conditions in urine, further promoting biofilm development. In conclusion, AAS-mediated c-di-GMP signaling and iron limitation are key drivers of biofilm formation by K. pneumoniae in urine, providing mechanistic insights that may guide strategies to disrupt biofilm formation.

Mechanistic insights into LuxS/AI-2 quorum sensing-regulated biofilm formation and its impact on the texture and flavor of kefir.

Biofilm synergy by Agrobacterium deltaense and Bacillus velezensis in co-cultures indicates bacterial interspecific cooperation.

Characterization of antimicrobial resistance and biofilm formation in Escherichia coli isolated from wild boars.

Staphylococcus aureus is the most common pathogen responsible for postoperative infections associated with cardiac implantable electronic devices (CIEDs), primarily due to its biofilm-forming capability on implant substrates. Protective envelopes, which sustain the local elution of antibiotics, significantly reduce the risk of CIED infection and biofilm formation. However, they are not equipped to counteract emerging bacterial resistance to antibiotics. Antimicrobial peptides (AMPs) can effectively erase contaminating bacteria, without eliciting resistance. Here, we explored the antimicrobial efficacy of biosynthesized cellulose (BC), a natural biopolymer used in protective envelopes, in combination with two synthetic AMPs: SET-M33D and Mastoparan X (MPX). The BC/AMPs combination inhibited bacterial attachment and subsequent biofilm formation significantly better than native BC or AMP coated titanium substrates, as revealed by full factorial design (FFD) experiments. The outcomes of FFD were used to develop a regression model that estimates the interaction between influential parameters and their impacts on response value. Furthermore, SEM imaging confirmed the superior antibiofilm activity of BC/SET-M33D compared to BC/MPX. We demonstrated that the protective function against S. aureus ATCC29213 may be linked to the downregulation of the biofilm associated gene icaA. The results reported demonstrate the feasibility of exploiting BC as AMP carrier for inhibiting biofilm formation in conditions relevant to deployment of CIEDs. While further in vivo evaluation is needed, this approach may offer a promising path to address antimicrobial resistance in the management of post-operative infections associated with CIED implant.

Biofilm formation and intra-pulsotype variability of Listeria monocytogenes at temperatures relevant to food processing environments.

Insights into the role of the two-component system pfeS/pfeR in Vibrio harveyi adaptation to host fish blood.

Understanding the probiotic potential of a healthy human vaginal flora, Lactobacillus gasseri K9: genomic and in vitro aspects

Various studies demonstrated that biofilm formation occurs in granular activated carbon (GAC) filters for (waste-)water treatment. However, little is known about how transient adsorptive interactions between organic solutes and the GAC within the filter bed influence biofilm development on the macroscale. This study proposes a numerical approach to simulate biofilm development in a GAC filter bed. For this purpose, a model approach for simulations at the single grain scale was extended to additionally account for spatial gradients along the filter bed length. The model was successfully tested with operational data from pilot-scale GAC filters. The subsequently simulated scenarios aimed at conceptually identifying key interactions between the GAC and biofilm formation, including spatial gradients in its composition. The simulation results showed that both heterotrophic and autotrophic microorganisms grew in GAC filters under typical operating conditions. The heterotrophs grew closer to the filter influent, consistent with the system's plug-flow-like behavior. Adsorption of organic solutes onto the GAC resulted in a stricter longitudinal separation of the two general types of microorganisms in the filter bed compared to a non-adsorbing reference filter bed by decreasing the downstream concentrations of organic substrate. Considering explicit backwash events further consolidated this separation for the GAC case. Together with the periodic adsorptive retention and release of organic solutes in the upper filter bed section, depending on the current biological activity, backwash events created even more favorable conditions for autotrophic growth in intermediate regions of the filter bed. Overall, the simulation results showed that autotrophic activity was locally enhanced by adsorptive effects of the GAC and that its extent was directly influenced by the simulated backwash regime. Considering the link between autotrophic activity and co-metabolic biotransformation of organic micropollutants discussed in literature, the results further highlight the potential biological contributions to the overall removal of certain micropollutants in GAC filters, but also the necessity to adequately represent longitudinal gradients and biofilm thickness control mechanisms in mathematical models.

Environmental Fitness and Human Pathogenicity Characteristics of Extended-Spectrum Cephalosporin-Resistant Escherichia coli Isolated from Danish Poultry Production.

Quorum sensing (QS) is a microbial population-density communication mechanism that coordinates gene expression, affecting virulence, biofilm formation, and food spoilage activities. Its disruption, termed quorum quenching (QQ), emerged as a promising strategy for mitigating microbial pathogenicity and enhancing food preservation. This review summarizes the main bacterial QS systems and addresses QQ mechanisms, with an emphasis on autoinducers degradation and competitive receptor antagonism, focusing on natural compounds with antivirulence potential. Special attention is given to applications in food science, where QS influences spoilage, safety, and the performance of starter cultures in fermentations. Evidence shows that phenolic compounds play a central role as natural QS inhibitors, attenuating bacterial communication without imposing selective pressure for resistance. Practical examples include reducing spoilage in food products, as well as controlling biofilm formation. We discuss challenges and future directions, emphasizing technological barriers and the valorization of agro-industrial byproducts as sustainable sources of bioactive compounds. • QS drives spoilage, virulence, and biofilm formation in food systems • Quorum quenching offers antivirulence control without selecting resistance • Phenolic compounds are key natural inhibitors of bacterial QS networks • QS-targeted strategies improve food safety and shelf-life • Encapsulation enables practical use of natural QS inhibitors in foods

Listeria monocytogenes (L. monocytogenes) is a pathogenic bacterium that poses a significant threat in food safety due to its ability to form resilient biofilms, contributing to cross-contamination risks in food processing environments. This study examines the role of the hly gene on biofilm formation and antibiotic resistance in L. monocytogenes. By generating a hly deletion mutant (Lm-Δhly), we investigated how the absence of this gene affects bacterial behavior and biofilm development. Our results revealed that hly deletion did not impact bacterial growth but significantly impaired biofilm formation. The Lm-Δhly strain exhibited a reduced biofilm biomass and a looser biofilm structure compared to the wild-type (WT) strain. Microscopic analysis, including SEM and CLSM, confirmed that biofilm architecture was compromised, with more viable cells in the WT biofilms and a substantial decrease in extracellular polymeric substances (EPS) in the mutant strain. Furthermore, the Lm-Δhly strain displayed reduced motility, auto-aggregation, and surface hydrophobicity, indicating a reduced ability to adhere and disseminate. Gene expression analysis revealed downregulation of key virulence factors such as prfA, sigB, and quorum sensing (QS) genes in the Lm-Δhly strain, suggesting that hly plays a role in their regulation. Antibiotic susceptibility testing revealed that the Lm-Δhly strain was more sensitive to ribosome-targeting antibiotics, including tetracycline and roxithromycin, correlating with impaired biofilm development under antibiotic stress. These findings emphasize the importance of hly in biofilm development, antibiotic resistance, and virulence regulation in L. monocytogenes. Targeting hly or its associated pathways may be a promising strategy to combat persistent L. monocytogenes contamination in food-related environments. Further investigation into hly' interactions with broader regulatory networks is needed to fully elucidate its role in L. monocytogenes pathogenesis.

Antibacterial and antibiofilm effects of boron-based nanomaterials: An innovative strategy against H. pylori.

The ability of bacterial pathogens to colonise indwelling medical devices, particularly urinary catheters, and to establish drug-resistant biofilms accounts for approximately 60 % of all nosocomial infections, underscoring the urgent need for effective strategies to mitigate biofilm development on catheter surfaces. In this study, we developed a multilayer nano-composite coating for urinary catheters, assembled via sequential deposition of bioadhesive catechol-functionalised chitosan (catCS), hyaluronic acid (HA), and antimicrobial aminated lignin nanoparticles (N-LigNPs). Sono-enzymatically phenolated, aminated, and formulated lignin nanoparticles (NPs) served as both structural and functional components within the coatings, whose assembly was monitored in real time using a quartz crystal microbalance with dissipation. Atomic force microscopy was employed to characterise the coating topography, complemented by surface zeta potential measurements and lubricity analysis. Cross-linking of N-LigNPs with catCS, catalysed by the oxidative enzyme laccase, increased the mechanical integrity of the coating beyond that afforded by electrostatic interactions alone. This translated into durable antimicrobial and antibiofilm performance of the functionalised catheters over 7 days in a hydrodynamic model simulating a catheterised human bladder, reducing S. aureus and Escherichia coli biofilm formation by more than 60 %, while exhibiting no cytotoxic effects on mammalian cells. Moreover, the clinical, histological, and microbiological data obtained from in vivo studies in a rabbit model demonstrated that the coating was biocompatible and effectively prevented catheter-associated urinary tract infections during a 10-day indwelling period. STATEMENT OF SIGNIFICANCE: Catheter-associated urinary tract infections (CAUTIs) remain a major clinical challenge due to biofilm formation and rising antimicrobial resistance. This study presents a bio-based, multilayer nanocomposite coating for urinary catheters that combines catechol-functionalised chitosan, hyaluronic acid, and aminated lignin nanoparticles, stabilised through laccase-mediated cross-linking. Unlike conventional electrostatic coatings, this enzymatically reinforced system exhibits enhanced mechanical durability, sustained antimicrobial and antibiofilm activity under physiologically relevant hydrodynamic conditions, and biocompatibility. Importantly, its efficacy is demonstrated both in vitro and in vivo. This work highlights a sustainable, antibiotic-sparing strategy with strong translational potential for preventing CAUTIs and could be extended to other biofilm-prone medical devices.

Transposon mutant library reveals the complex regulatory network of biofilm formation in Vibrio parahaemolyticus.

Characterization of biocorrosion by sulfate-reducing bacteria in extra-alveolar mini-implants installed in ex vivo human mandibles and exposed to the oral consortium of Desulfovibrio fairfieldensis: Microbiological, morphological, and mass loss analysis.

Dry surface biofilm of Salmonella and Cronobacter sakazakii: a real concern for the low moisture food industry.

Small RNA-mediated regulation of stress tolerance in Deinococcus radiodurans.