Biology subjects

de Souza-Guerreiro, T. C.

Publications and source records attributed to de Souza-Guerreiro, T. C..

3 recordsLinked to original sources

bioRxiv2026

A Dipolar Photoswitch Modulates Bacterial Membrane Potential and Reveals Context-dependent Bioelectrical Circuitry

Dynamic bioelectric signalling in bacteria regulates physiology and collective behaviours, yet tools to perturb microbial membrane voltage with high spatiotemporal control remain limited. Here we introduce MTP2, a non-genetic, membrane-targeting azobenzene photoswitch that enables optical modulation of bacterial membrane potential by tuning interfacial electrostatics in Bacillus subtilis. MTP2 associates strongly with the cell envelope and shifts the resting potential to more negative values in the dark, while 470-nm illumination evokes a robust, reversible depolarization at the single-cell level. Although MTP2 photoisomerization is ultrafast (picoseconds), the voltage waveforms unfold over seconds to minutes, indicating that the response is set by homeostatic ion transport rather than by MTP2 photochemistry. Genetic and pharmacological perturbations show that K+ conductance, Cl--sensitive pathways, and active transport reshape the amplitude, kinetics and even polarity of the optical response, revealing a context-dependent interplay between a passive molecular perturbation and endogenous bioelectric circuitry. As a functional proof of concept, kanamycin efficacy co-varies with the optically tuned voltage state. Together, these results establish MTP2 as a reversible chemical optostimulator for probing and controlling microbial electrophysiology.

microbiology↗

bioRxiv2023

Bioelectrical antimicrobial susceptivity testing (BeAST) with the budding yeast S. cerevisiae

Membrane potential is a useful marker for antimicrobial susceptibility testing (AST) due to the fundamental characteristic of vital cells. However, the difficulties associated with measuring the membrane potential in microbes restrict its broad application. In this study, we present Bioelectrical AST (BeAST) using the model fungus Saccharomyces cerevisiae. Using fluorescent indicators (DiBAC4(3), ThT and TMRM), we measured plasma and mitochondrial membrane-potential dynamics upon electric stimulation. We find that a 2.5-second electric stimulation induces hyperpolarisation of plasma membrane lasting 20 minutes in vital S. cerevisiae, but depolarisation in inhibited cells. The numerical simulation of FitzHugh-Nagumo model successfully recapitulates vitality-dependent dynamics. The model also suggests that the magnitude of plasma-membrane potential dynamics (PMD) correlates with the degree of inhibition. To test this prediction and to examine if BeAST can be used for assessing novel anti-fungal compounds, we treat cells with biogenic silver nanoparticles (bioAgNPs) synthesised using orange fruit flavonoids and Fusarium oxysporum. Comparing BeAST with optical density assay with various stressors, we show that PMD correlates with the severityof growth inhibitions. These results suggest that BeAST holds promise for screening anti-fungal compounds, offering a valuable approach to tackling antimicrobial resistance.

microbiology↗

bioRxiv2022

Membrane Targeted Azobenzene Drives Optical Modulation of Bacterial Membrane Potential

Recent studies have shown that bacterial membrane potential is dynamic and plays signalling roles. Yet, little is still known about the mechanisms of bacterial membrane potential regulation -owing in part to a scarcity of appropriate research tools. Optical modulation of bacterial membrane potential could fill this gap and provide a new approach to studying and controlling bacterial physiology and electrical signalling. Here, we show that a membrane-targeted azobenzene (Ziapin2) can be used to photo-modulate the membrane potential in cells of the Gram-positive bacterium Bacillus subtilis. We found that upon exposure to blue-green light ({lambda} = 470 nm), isomerization of Ziapin2 in the bacteria membrane induces hyperpolarisation of the potential. In order to investigate the origin of this phenomenon we examined ion-channel-deletion strains and ion channel blockers. We found that in presence of the chloride channel blocker idanyloxyacetic acid-94 (IAA-94) or in absence of KtrAB potassium transporter, the hyperpolarisation response is attenuated. These results reveal that the Ziapin2 isomerization can induce ion channel opening in the bacterial membrane, and suggest that Ziapin2 can be used for studying and controlling bacterial electrical signalling. This new optical tool can contribute to better understand microbial phenomena, such as biofilm electric signalling and antimicrobial resistance.

biophysics↗