Fluorescent labelling negatively affects the physiology of Lactococcus lactis

Protective Effect of Chinese Bayberry (Myrica rubra Sieb. et Zucc.) Pomace Wine on Oxidative Stress of Hydrogen Peroxide by Regulating Keap1/Nrf2 Pathway in HepG2 Cells

Chinese bayberry (Myrica rubra Sieb. et Zucc.) pomace wine (CPW) is fruity and rich in bioactive compounds, with high nutritional value and antioxidant activities. This study aims to investigate the protective effect of CPW on the oxidative damage induced by hydrogen peroxide in human hepatocellular carcinoma (HepG2) cells and CPW's possible underlying mechanism. The fluorescence assay results revealed that CPW pre-treatment inhibited intracellular reactive oxygen species (ROS) accumulation in H₂O₂-induced HepG2 cells and cell membrane injury. Meanwhile, CPW remarkably enhanced the activity of antioxidant enzymes including superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GR), and the content of glutathione (GSH). Moreover, CPW pretreatment significantly regulated the expression of Kelch-like ECH-associated protein 1 (Keap1)/nuclear factor erythroid 2-related factor 2 (Nrf2) pathway-associated genes (Keap1, Nrf2, NADPH quinone oxidoreductase I (NQO1), and heme oxygenase-1 (HO-1)) and its downstream antioxidant genes (SOD, CAT, GSH, and the glutamate-cysteine ligase catalytic (GCLC) subunit) in HepG2 cells. These data demonstrated that CPW prevented H₂O₂-induced oxidative stress by regulating the Keap1/Nrf2 signaling pathway.

Reevaluating multicolor flow cytometry to assess microbial viability

Flow cytometry is a rapid and quantitative method to determine bacterial viability. Although different stains can be used to establish viability, staining protocols are inconsistent and lack a general optimization approach. Very few "true" multicolor protocols, where dyes are combined in one sample, have been developed for microbiological applications. In this mini-review, the discrepancy between protocols for cell-permeant nucleic acid and functional stains are discussed as well as their use as viability dyes. Furthermore, optimization of staining protocols for a specific setup are described. Original data using the red-excitable SYTO dyes SYTO 59 to 64 and SYTO 17, combined with functional stains, for double and triple staining applications is also included. As each dye and dye combination behaves differently within a certain combination of medium matrix, microorganism, and instrument, protocols need to be tuned to obtain reproducible results. Therefore, single, double, and triple stains are reviewed, including the different parameters that influence staining such as stain kinetics, optimal stain concentration, and the effect of the chelator EDTA as membrane permeabilizer. In the last section, we highlight the need to investigate the stability of multicolor assays to ensure correct results as multiwell autoloaders are now commonly used.