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Bacterial biofilms represent a prominent biological barrier against physical and chemical attacks. Disturbing the anaerobic microenvironment within biofilms by co-delivery of oxygen appears as a promising strategy to enhance the activity of an antibiotic. Here, we report the effect of oxygen-producing calcium peroxide nanoparticles (CaO 2 NP) in combination with tobramycin sulfate (Tob). On Pseudomonas aeruginosa PAO1 biofilms in vitro, the additive effect of CaO 2 NP towards Tob activity enhanced biofilm eradication by 2 log compared to Tob alone. For natural biofilms grown in the oral cavity of human volunteers in situ, treatment by CaO 2 NP alone slightly increased the fraction of dead bacteria from 44% in various controls, including Tob alone, to 57%. However, the combination of CaO 2 NP with Tob further increased the fraction of dead bacteria to 69%. These data confirm the intrinsic antimicrobial and antibiotic-potentiating effect of CaO 2 NP also in a clinically relevant setting., (© 2024. The Author(s).)

Biofilm formation by Shewanella oneidensis has been extensively studied under oxic conditions; however, relatively little is known about biofilm formation under anoxic conditions and how biofilm architecture and composition can positively influence current generation in bioelectrochemical systems. In this study, we utilized a recently developed microfluidic biofilm analysis setup with automated 3D imaging to investigate the effects of extracellular electron acceptors and synthetic modifications to the extracellular polymeric matrix on biofilm formation. Our results with the wild type strain demonstrate robust biofilm formation even under anoxic conditions when fumarate is used as the electron acceptor. However, this pattern shifts when a graphite electrode is employed as the electron acceptor, resulting in biofilm formation falling below the detection limit of the optical coherence tomography imaging system. To manipulate biofilm formation, we aimed to express BpfG with a single amino acid substitution in the catalytic center (C116S) and to overexpress bpfA. Our analyses indicate that, under oxic conditions, overarching mechanisms predominantly influence biofilm development, rather than the specific mutations we investigated. Under anoxic conditions, the bpfG mutation led to a quantitative increase in biofilm formation, but both strains exhibited significant qualitative changes in biofilm architecture compared to the controls. When an anode was used as the sole electron acceptor, both the bpfA and bpfG mutations positively impacted mean current density, yielding a 1.8-fold increase for each mutation., (© 2024. The Author(s).)

The creation of free-standing lipid membranes has been so far of remarkable interest to investigate processes occurring in the cell membrane since its unsupported part enables studies in which it is important to maintain cell-like physicochemical properties of the lipid bilayer, that nonetheless depend on its molecular composition. In this study, we prepare pore-spanning membranes that mimic the composition of plasma membranes and perform force spectroscopy indentation measurements to unravel mechanistic insights depending on lipid composition. We show that this approach is highly effective for studying the mechanical properties of such membranes. Furthermore, we identify a direct influence of cholesterol and sphingomyelin on the elasticity of the bilayer and adhesion between the two leaflets. Eventually, we explore the possibilities of imaging in the unsupported membrane regions. For this purpose, we investigate the adsorption and movement of a peripheral protein, the fibroblast growth factor 2, on the complex membrane., Competing Interests: The authors declare no competing financial interest., (This journal is © The Royal Society of Chemistry.)

FGF2 is a cell survival factor involved in tumor-induced angiogenesis that is secreted through an unconventional secretory pathway based upon direct protein translocation across the plasma membrane. Here, we demonstrate that both PI(4,5)P2-dependent FGF2 recruitment at the inner plasma membrane leaflet and FGF2 membrane translocation into the extracellular space are positively modulated by cholesterol in living cells. We further revealed cholesterol to enhance FGF2 binding to PI(4,5)P2-containing lipid bilayers. Based on extensive atomistic molecular dynamics (MD) simulations and membrane tension experiments, we proposed cholesterol to modulate FGF2 binding to PI(4,5)P2 by (i) increasing head group visibility of PI(4,5)P2 on the membrane surface, (ii) increasing avidity by cholesterol-induced clustering of PI(4,5)P2 molecules triggering FGF2 oligomerization, and (iii) increasing membrane tension facilitating the formation of lipidic membrane pores. Our findings have general implications for phosphoinositide-dependent protein recruitment to membranes and explain the highly selective targeting of FGF2 toward the plasma membrane, the subcellular site of FGF2 membrane translocation during unconventional secretion of FGF2., (© 2022 Lolicato et al.)

The salivary pellicle is a thin acellular film formed on orally exposed surfaces by adsorption of macromolecules from the oral fluids and serves as a protective layer in the maintenance of oral health. Pellicle thickness measurements are a central tool helping to understand how exogenous manipulations may influence pellicle formation. This is of particular importance for the investigation of new preventive and therapeutic approaches. In the present study we determined the kinetics of the in situ pellicle thickness formation at different intraoral sites and investigated how pellicle formation occurs in different individuals. To address the kinetic aspect, the thickness of the in situ pellicle was determined after formation periods of 3 min, 30 min and 120 min. The thickness of the pellicle was either measured on silicon wafers by ellipsometry or on bovine enamel by transmission electron microscopy. We found a physiologically important rapid pellicle formation phase within the first minutes and a slow pellicle formation phase between 30 min and 120 min. Furthermore, our results identify significant inter-individual differences both for the pellicle thickness and for the formation kinetics, indicating the consideration of individual-specific differences of the pellicle layer as an important aspect for future studies., (Copyright © 2018 Elsevier B.V. All rights reserved.)

The adhesive and mechanical properties of a modular fusion protein consisting of two different types of binding units linked together via a flexible resilin-like-polypeptide domain are quantified. The adhesive domains have been constructed from fungal cellulose-binding modules (CBMs) and an amphiphilic hydrophobin HFBI. This study is carried out by single-molecule force spectroscopy, which enables stretching of single molecules. The fusion proteins are designed to self-assemble on the cellulose surface, leading into the submonolayer of proteins having the HFBI pointing away from the surface. A hydrophobic atomic force microscopy (AFM) tip can be employed for contacting and lifting the single fusion protein from the HFBI-functionalized terminus by the hydrophobic interaction between the tip surface and the hydrophobic patch of the HFBI. The work of rupture, contour length at rupture and the adhesion forces of the amphiphilic end domains are evaluated under aqueous environment at different pHs., Competing Interests: The authors declare no competing financial interest.

Adhesion is a key issue for researchers of various fields, it is therefore of uppermost importance to understand the parameters that are involved. Commonly, only surface parameters are employed to determine the adhesive forces between materials. Yet, van der Waals forces act not only between atoms in the vicinity of the surface, but also between atoms in the bulk material. In this review, we describe the principles of van der Waals interactions and outline experimental and theoretical studies investigating the influence of the subsurface material on adhesion. In addition, we present a collection of data indicating that silicon wafers with native oxide layers are a good model substrate to study van der Waals interactions with coated materials., (Copyright © 2012 Elsevier B.V. All rights reserved.)