CO2 enhances the formation, nutrient scavenging and drug resistance properties of C. albicans biofilms

C. albicans is the predominant human fungal pathogen and frequently colonises medical devices, such as voice prostheses, as a biofilm. It is a dimorphic yeast that can switch between yeast and hyphal forms in response to environmental cues, a property that is essential during biofilm establishment and maturation. One such cue is the elevation of CO2 levels, as observed in exhaled breath for example. However, despite the clear medical relevance, the effect of CO2 on C. albicans biofilm growth has not been investigated to date. Here we show that physiologically relevant CO2 elevation enhances each stage of the C. albicans biofilm-forming process: from attachment through maturation to dispersion. The effects of CO2 are mediated via the Ras/cAMP/PKA signalling pathway and the central biofilm regulators Efg1, Brg1, Bcr1 and Ndt80. Biofilms grown under elevated CO2 conditions also exhibit increased azole resistance, increased Sef1-dependent iron scavenging and enhanced glucose uptake to support their rapid growth. These findings suggest that C. albicans has evolved to utilise the CO2 signal to promote biofilm formation within the host. We investigate the possibility of targeting CO2-activated processes and propose 2-deoxyglucose as a drug that may be repurposed to prevent C. albicans biofilm formation on medical airway management implants. We thus characterise the mechanisms by which CO2 promotes C. albicans biofilm formation and suggest new approaches for future preventative strategies.

Restless motion

Atoms in solids are in constant random motion. Their kinetic energy is heat. Heat associated with local regions may fluctuate. The size of the fluctuations increases with decreasing size of the region. Such fluctuations enable thermally activated processes to occur. At equilibrium interstitials and vacancies undergo random walks in solids, which gives rise to diffusion in crystals and reptation in polymers. The activation energy is the free energy barrier these defects have to overcome to jump between sites. Diffusion is biased by driving forces resulting from gradients of chemical potential. The mobility relates the drift velocity of defects to the driving force on them. The Einstein relation relates the mobility to the diffusivity. It is an example of the fluctuation-dissipation theorem. Atomic motion enables diffusion and limits mobility. Thermal expansion is also a consequence of atomic motion, resulting from a fundamental asymmetry in all interatomic forces.

Studying the Thermally Activated Processes Operating during Deformation of hcp and bcc Mg–Li Metal-Matrix Composites

Stress-relaxation tests were performed during plastic deformation at room temperature of three magnesium Mg–Li alloys reinforced with 10 vol% of short Saffil fibers. For comparison, the composite with the Mg matrix was studied. The time dependencies of the stress decrease were analyzed with the aim to determine the activation volume and the main types of thermally activated processes occurring during plastic flow. The Mg4Li matrix alloy exhibited the hcp structure, while the composite with the Mg12Li matrix alloy had the bcc structure. The third alloy, Mg8Li, combined both phases, hcp and bcc. The stress acting in the matrix was divided into two components: the internal stress and the effective stress. Activation volume and stress-sensitivity parameters were determined as a function of effective stress and strain. While the values of the activation volume depending on the effective stress lay on one “master” curve, the strain dependence was different for all materials. The main thermally activated process in the hcp structure was the dislocation motion in the noncompact planes, while in the bcc structure, massive recovery processes connected with an increase in dislocations were identified.

Механизмы термостимулированной люминесценции в УФ-облученных нанотрубках диоксида циркония

A nanotubular layer of zirconium dioxide was synthesized with anodic oxidation. Curves of spectrally resolved thermostimulated luminescence were studied in the 390-550 nm range after 300 nm UV irradiation. Energetic and kinetic parameters of thermostimulated luminescence curves were estimated. The mechanism of thermally-activated processes involving intrinsic lattice defects is proposed.

Thermally activated processes in an organic long-persistent luminescence system

Organic long-persistent luminescence (OLPL) was achieved through photo-induced charge separation, charge accumulation, and emission from charge recombination. The presence of thermal activation processes in the OLPL system was confirmed.

Strengthening and Thermally Activated Processes in an AX61/Saffil Metal Matrix Composite

AX61 magnesium alloy was reinforced with short Saffil fibres using squeeze cast technology. Samples were cut from the casting in two directions: parallel and perpendicular to the fibre plane. Samples were deformed in compression at various temperatures from room temperature to 300 °C. Various strengthening mechanisms such as load transfer, increased dislocation density, Orowan and Hall–Petch strengthening were analysed. During deformation, the stress relaxation tests were subsequently performed. The relaxation curves were evaluated with respect to Li and Feltham equations with the aim to find stress components in matrix and parameters of the thermally activated process(es).

CO2 enhances the ability of Candida albicans to form biofilms, overcome nutritional immunity and resist antifungal treatment

C. albicans is the predominant fungal pathogen of humans and frequently colonises medical devices, such as voice prosthesis, as a biofilm. It is a dimorphic yeast that can switch between yeast and hyphal forms in response to environmental cues, a property that is essential during biofilm establishment and maturation. One such cue is the elevation of CO2 levels, as observed in exhaled breath.. However, despite the clear medical relevance, the effects of CO2 on C. albicans biofilm growth has not been investigated to date. Here, we show that physiologically relevant CO2 elevation enhances each stage of the C. albicans biofilm forming process;from attachment through to maturation and dispersion.. The effects of CO2 are mediated via the Ras/cAMP/PKA signalling pathway and the central biofilm regulators Efg1, Brg1, Bcr1 and Ndt80. Biofilms grown under elevated CO2 conditions also exhibit increased azole resistance, tolerance to nutritional immunity and enhanced glucose uptake to support their rapid growth. These findings suggest that C. albicans has evolved to utilise the CO2 signal to promote biofilm formation within the host. We investigate the possibility of targeting CO2 activated processes and propose 2-Deoxyglucose as a drug that may be repurposed to prevent C. albicans biofilm formation on medical airway management implants. We thus characterise the mechanisms by which CO2 promotes C. albicans biofilm formation and suggest new approaches for future preventative strategies.