Biological Effects Of Nano-ZnO And Nano-Ag On Aerobic Denitrifying Bacteria

Since the 21st century,nanoparticles have been widely used in the chemical industry,electronics industry,medical and health industry,aerospace,water treatment and military.Along with the widespread production and use of nanoparticles in life,it will inevitably lead to the entry into the water environment due to human or non-human factors during production,transportation,use and disposal.Most of the engineered nanoparticles enter the water through the sewage collection pipe network and are processed centrally in the sewage treatment plant.This has brought tremendous pressure to the sewage treatment system.Many scholars have been working on the effects of nanoparticles on wastewater treatment systems.However,the studies about the influence of nanoparticles on the function of water treatment bacteria and the adaptability mechanism of water treatment bacteria to the stress of nanoparticles are urgently needed.In this paper,the typical nanoparticle AgNPs and ZnONPs were used to study the effect of nanoparticles on the physiological and biochemical functions of aerobic denitrifying bacteria,the mechanism of bacterial toxicity and the response mechanism of bacteria to the nanoparticle environment,by using the aerobic denitrifying bacteria Enterobacter cloacae strain HNR as the representative bacteria.Studies on the effect of nanoparticles on the physiological and biochemical functions have found that:the growth cycle of bacteria was delayed;the N03-N reducing ability and NO2--N reducing ability of bacteria were inhibited;the exercise capacity decreased with the increase of nanoparticle concentrationStudies on the mechanism of toxicity of nanoparticles have found that the toxicity mechanism of metal nanoparticles mainly includes:generating metal ions,reacting metal ions with bacteria,inhibiting the bacterial activity;stimulating bacterial intracellular ROS,inhibiting certain enzyme activities of bacteria;inhibiting the key enzymes of bacteria Activity,affecting the growth of bacteriaStudies on bacterial extracellular polymers(EPS)have found that under the stimulation of nanoparticles,the ability of bacteria to form a membrane was greatly increased;the amount of EPS secretion was increased,and extracellular protein synthesis was increasedThe expression of oxidative stress-related enzymes such as iron carrier protein,glutathione peroxidase,glutathione S transferase,chloride catalase,pyruvate dehydrogenase and the like were significantly up-regulated.In this paper,the effect of nanoparticles on the physiological and biochemical functions of HNR,the toxic effects of nanoparticles on HNR,and the adaptation mechanism of bacteria were analyzed.It was of great significance to explore the influence of NPs on sewage treatment system,and provided a scientific basis for reducing the influence of nanoparticles on nitrogen-depleting microorganisms.