Search

Fermentation products of Lysobacter antibioticus 13-6 have antagonistic activity against devastating phytopathogenic bacerium Xanthomonas oryzae pv. oryzicola. The production of Lysobacter antibioticus 13-6 secondary metabolites was increased by optimizing the fermentation medium; using a single-factor screening test, Plackett–Burman Design, and Box-Behnken Design. The medium's final formulation for active secondary metabolites high-yield included peptone 5 g/L, glucose 4.73 g/L, MgSO4·7H2O 2.33 g/L, and K2HPO4 2.21 g/L. We compared phenazine-1-carboxylic acid (PCA) contents of L. antibioticus 13-6 in the initial and optimized mediums through HPLC. It was found PCA contents of the optimized medium are two folds more than in the initial medium. We also detected the relative expression of five phenazine genes of L. antibioticus 13-6 via RT-qPCR, and it was found that genes: phzB, C, S, and NO1 have more significant expression compared with the initial medium, while gene phzD has found just significant. Further, we revealed that the optimal fermentation conditions for secondary metabolites were: fermentation time 60 hours, shaking speed 160 rpm, inoculum size 3%, and the initial pH = 7.0. In the end, it was determined that the antimicrobial activity and quality of L. antibioticus 13-6 secondary metabolites were increased by about 41.75% and 2-times, respectively, after the optimization of the fermentation medium. [ABSTRACT FROM AUTHOR]

SCN10A /Na V 1.8 may be associated with a lower risk of ventricular fibrillation in the setting of acute myocardial infarction (AMI), but if and by which mechanism Na V 1.8 impacts on ventricular electrophysiology is still a matter of debate. The purpose of this study was to elucidate the contribution of Na V 1.8 in ganglionated plexi (GP) to ventricular arrhythmias in the AMI model. Twenty beagles were randomized to either the A-803467 group ( n = 10) or the control group ( n = 10). Na V 1.8 blocker (A-803467, 1 μmol/0.5 mL per GP) or DMSO (0.5 mL per GP) was injected into four major GPs. Ventricular effective refractory period, APD 90 , ventricular fibrillation threshold, and the incidence of ventricular arrhythmias were measured 1 h after left anterior descending coronary artery occlusion. A-803467 significantly shortened ventricular effective refractory period, APD 90 , and ventricular fibrillation threshold compared to control. In the A-803467 group, the incidence of ventricular arrhythmias was significantly higher compared to control. A-803467 suppressed the slowing of heart rate response to high-frequency electrical stimulation of the anterior right GP, suggesting that A-803467 could inhibit GP activity. SCN10A /Na V 1.8 was readily detected in GPs, but was not validated in ventricles by quantitative RT-PCR, western blot and immunohistochemistry. While SCN10A /Na V 1.8 is detectible in canine GPs but not in ventricles, blockade of Na V 1.8 in GP increases the incidence of ventricular arrhythmias in AMI hearts. Our study shows for the first time an influence of SCN10A /Na V 1.8 on the regulation of ventricular arrhythmogenesis via modulating GP activity in the AMI model., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Qi, Dai, Song, Shen, Li, Wei, Zhang, Nie, Lin, Cai and Ge.)