During the last decade green synthesized cerium oxide nanoparticles (CeO 2 NPs) attracted remarkable interest in various fields of science and technology. This review, explores the vast array of biological resources such as plants, microbes, and other biological products being used in synthesis of CeO 2 NPs. It also discusses their biosynthetic mechanism, current understandings, and trends in the green synthesis of CeO 2 NPs. Novel therapies based on green synthesized CeO 2 NPs are illustrated, in particular their antimicrobial potential along with attempts of their mechanistic elucidation. Overall, the main objective of this review is to provide a rational insight of the major accomplishments of CeO 2 NPs as novel therapeutics agents for a wide range of microbial pathogens and combating other diseases.

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Hospital wastewater is a major contributor of disease-causing microbes and the emergence of antibiotic resistant bacteria. In this study, thiolated iron-doped nanoceria was synthesised and tested for killing of microbes from hospital effluent. These particles were designed to inhibit the efflux pumps of the bacteria found in hospital effluent with further ability to activate in visible light via iron doping thus generating tunable amount of reactive oxygen species (ROS). The quantum yield of the ROS generated by the nanoceria was 0.67 while the ROS types produced were singlet oxygen (36%), hydroxyl radical (31%) and hydroxyl ions (32%), respectively. The particles were initially synthesised through green route using Foeniculum vulgare seeds extract and were annealed at 200°C and further coated with thiolated chitosan to enhance the solubility and efflux pump inhibition. X-ray diffraction confirmed the polycrystalline nature of nanoparticles and uniform spherical shape with 30 nm size, confirmed by scanning electron microscope. The nanoparticles exhibited 100% bactericidal activity at 100 µg/mL against all the isolated bacteria. The enhanced bactericidal effect of iron-doped nanoceria could be attributed to efflux inhibition via thiolated chitosan as well as the production of ROS upon illumination in visible light, causing oxidative stress against microbes found in hospital effluent.

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The survival of microbes in various severe condition leads to developments in the medical, agricultural, and bioenergy sectors. In this study we isolate, identify and characterize salt tolerant bacteria from saline areas. Sample was taken from hyper saline areas of KP. Four bacterial isolates were isolated from sample and different techniques were applied. All the bacterial isolates were able to grow on agar media in the presence of salt this shows the strict halotolerant nature of isolates. Serial dilution was performed to check the salt concentration at which minimum and maximum growth occurs. The growth of isolates was inversely proportional to salt concentration in media as the concentration of salt in media was increases the growth of isolates were decreases and vice versa. Only one isolate was able to show resistance to 2.5M salt in media and 3 isolates were able to show resistance to 2M salt in media. Gram staining was performed to check that the isolates are gram positive or gram negative; all of the isolates were gram positive. For molecular analysis genomic DNA was extracted and checks the result on gel.