Fe2+ Alleviated the Toxicity of ZnO Nanoparticles to Pseudomonas tolaasii Y-11 by Changing Nanoparticles Behavior in Solution

Acid-tolerant Pseudomonas citronellolis YN-21 exhibits a high heterotrophic nitrification capacity independent of the amo and hao genes

Heterotrophic nitrifying bacteria are found to be promising candidates for implementation in wastewater treatment systems due to their tolerance to extreme environments. A novel acid-resistant bacterium, Pseudomonas citronellolis YN-21, was isolated and reported to have exceptional heterotrophic nitrification capabilities in acidic condition. At pH 5, the highest NH4+ removal rate of 7.84 mg/L/h was displayed by YN-21, which was significantly higher than the NH4+ removal rates of other strains in neutral and alkaline environments. Remarkably, a distinct accumulation of NH2OH and NO3- was observed during NH4+ removal by strain YN-21, while traditional amo and hao genes were not detected in the genome, suggesting the possible presence of alternative nitrifying genes. Moreover, excellent nitrogen removal performance was displayed by YN-21 even under high concentrations of metal ion stress. Consequently, a broad application prospect in the treatment of leather wastewater and mine tailwater is offered by YN-21.

Biosynthesis of silver nanoparticles using Pseudomonas canadensis, and its antivirulence effects against Pseudomonas tolaasii, mushroom brown blotch agent

This study reports the biosynthesis of silver nanoparticles (AgNPs) using a Pseudomonas canadensis Ma1 strain isolated from wild-growing mushrooms. Freshly prepared cells of P. canadensis Ma1 incubated at 26-28 °C with a silver nitrate solution changed to a yellowish brown color, indicating the formation of AgNPs, which was confirmed by UV-Vis spectroscopy, scanning electron microscopy (SEM), and X-ray diffraction. SEM analysis showed spherical nanoparticles with a distributed size mainly between 21 and 52 nm, and the XRD pattern revealed the crystalline nature of AgNPs. Also, it provides an evaluation of the antimicrobial activity of the biosynthesized AgNPs against Pseudomonas tolaasii Pt18, the causal agent of mushroom brown blotch disease. AgNPs were found to be bioactive at 7.8 μg/ml showing a minimum inhibitory concentration (MIC) effect against P. tolaasii Pt18 strain. AgNPs at the MIC level significantly reduced virulence traits of P. tolaasii Pt18 such as detoxification of tolaasin, various motility behavior, chemotaxis, and biofilm formation which is important for pathogenicity. Scanning electron microscopy (SEM) revealed that bacterial cells treated with AgNPs showed a significant structural abnormality. Results showed that AgNPs reduced brown blotch symptoms in vivo. This research demonstrates the first helpful use of biosynthesized AgNPs as a bactericidal agent against P. tolaasii.