Membrane Depolarization and Apoptosis-Like Cell Death in an Alkaline Environment in the Rice Pathogen Burkholderia glumae

Visible light-activated dye-sensitized TiO2 antibacterial film: A novel strategy for enhancing food safety and quality

Antibacterial packaging holds promise in addressing food spoilage by inactivating bacteria, but current antimicrobial packaging solutions face challenges like depletion of antibacterials and concerns of antibiotic abuse. In response to these limitations of existing packaging materials, we developed a novel antibacterial packaging film by incorporating titanium dioxide (TiO2)- tetra(4-carboxyphenyl) porphyrin (TcPP) conjugates into cellulose nanofibrils (CNF) films. Unlike conventional antimicrobial packaging, this film harnesses visible light energy to excite electrons from TcPP to TiO2, generating reactive oxygen species (ROS) that inactivate bacteria without relying on antibiotics. Results demonstrated that the film reduced 4.5, 4.6, 4.1, and 4.7-log Escherichia coli, Pseudomonas fluorescens, Leuconostoc lactis, and Listeria innocua, respectively, in phosphate-buffered saline within 72 h under 6000 lux light (3.13 mW/cm2). The antimicrobial efficacy decreased as the light intensity decreased. Notably, it retains significant antimicrobial properties even under an extremely low light intensity of 600 lux (0.60 mW/cm2). The analysis also revealed that singlet oxygen and hydrogen peroxide are the major generated ROS from the film under light exposure. When applied to cucumbers, the film reduced E. coli by 3.5 logs after 48-hour light exposure. The designed photocatalytic antibacterial film represents a major advancement in sustainable food preservation, reducing food waste by extending the shelf life of fresh produce.

Flow cytometry: Aspects and application in plant and biological science

Flow cytometry is a potent method that enables the quick and concurrent investigation of several characteristics of single cells in solution. Photodiodes or photomultiplier tubes are employed to detect the dispersed and fluorescent light signals that are produced by the laser beam as it passes through the cells. Photodetectors transform the light signals produced by the laser into electrical impulses. A computer then analyses these electrical impulses to identify and measure the various cell populations depending on their fluorescence or light scattering characteristics. Based on their fluorescence or light scattering properties, cell populations can be examined and/or isolated. This review covers the basic principle, components, working and specific biological applications of flow cytometry, including studies on plant, cell and molecular biology and methods employed for data processing and interpretation as well as the potential future relevance of this methodology in light of retrospective analysis and recent advancements in flow cytometry.

A membrane protein of the rice pathogen Burkholderia glumae required for oxalic acid secretion and quorum sensing

Bacterial panicle blight is caused by Burkholderia glumae and results in damage to rice crops worldwide. Virulence of B. glumae requires quorum sensing (QS)-dependent synthesis and export of toxoflavin, responsible for much of the damage to rice. The DedA family is a conserved membrane protein family found in all bacterial species. B. glumae possesses a member of the DedA family, named DbcA, which we previously showed is required for toxoflavin secretion and virulence in a rice model of infection. B. glumae secretes oxalic acid as a "common good" in a QS-dependent manner to combat toxic alkalinization of the growth medium during the stationary phase. Here, we show that B. glumae ΔdbcA fails to secrete oxalic acid, leading to alkaline toxicity and sensitivity to divalent cations, suggesting a role for DbcA in oxalic acid secretion. B. glumae ΔdbcA accumulated less acyl-homoserine lactone (AHL) QS signalling molecules as the bacteria entered the stationary phase, probably due to nonenzymatic inactivation of AHL at alkaline pH. Transcription of toxoflavin and oxalic acid operons was down-regulated in ΔdbcA. Alteration of the proton motive force with sodium bicarbonate also reduced oxalic acid secretion and expression of QS-dependent genes. Overall, the data show that DbcA is required for oxalic acid secretion in a proton motive force-dependent manner, which is critical for QS of B. glumae. Moreover, this study supports the idea that sodium bicarbonate may serve as a chemical for treatment of bacterial panicle blight.