Fate Of Antibiotics And Antibiotic Resistance Genes During The Resource Utilization Of Manure

Veterinary antibiotics(VAs)are widely used for growth enhancement,production,and in the prevention and treatment of infectious diseases in the livestock and poultry industry.Their emergence into the agroenvironment began during the resource utilization of farmyard and poultry manure.However,these bioactive organic pollutants are not easily degradable in the natural environment and can be uptaken by plants,eventually ending up in the human food chain.Despite the danger,these antibiotics pose,unfortunately,it is an issue that still remains underreported and current work for animal manure processing is not up to the required standards and hence is not supposed to reflect the actual performance in antibiotic resistant genes(ARGs)control.It is worth noting that the rebounding of ARGs and the succession of the bacterial community during conventional aerobic composting are serious threats.Considering the probable risk,this study was designed to monitor how thermophilic aerobic composting affects the ARGs,as well as the bacterial diversity during the composting of cow manure.In this study,several sets of experiments were performed and three levels of sulfamethoxazole(SMX)(Control,25 mg/kg,50 mg/kg,and 100 mg/kg)were used a typical antibiotic from the sulfonamides class.During the investigation of antibiotics degradation,we found that the SMX degradation was enhanced during thermophilic aerobic composting and followed concentration-dependent order(control > SMX25 > SMX50 > SMX100)and was no longer detected after 20 days of thermophilic aerobic composting.Thermophilic temperature or heat significantly stimulated the rebounding of certain genes and after 35 days of the composting procedure,the abundance of detected genes(sul2,sul A,dfr A7,and dfr A1)significantly decreased(p < 0.05)in control and spiked-antibiotic treatments,except for sul1.It was also found that the addition of three concentrations of SMX elicited a sharp effect on bacterial diversity,and microbial structure in SMX25 led to significant differences in others(p < 0.05).The network analysis revealed more rigorous interactions among ARGs and abundant genera,suggesting that a host of ARGs potentially increased at low concentrations of sulfamethoxazole.Especially,genera g?norank?f??Beggiatoaceae,Ruminiclostridium,Caldicoprobacter,g?norank?o?MBA03,Hydrogenispora,and Ruminiclostridium?1 were major potential hosts for sul1.The second batch of the experiment was based on stage-specific temperature-controlled aerobic composting.The results of four different treatments demonstrated that temperature,water content,C/N ratio,EC,and p H showed no significant(p > 0.05)difference.ARGs significantly decreased in the initial 10 days of the thermophilic phase,but the abundance of sul1 and sul2 increased greatly after 30 days.Moreover,ARGs were closely related with each other during the late stages of composting.Third section explored the effect of SMX on the enzymatic activities of cellulase,protease,urease,and arylsulfatase.Compost samples were taken at three different intervals for analysis(day 0,day 25,and day 45).The findings revealed that at the start of the composting process,a strongly negative effect on enzymatic behavior was observed,and this response was significantly dependent on SMX concentrations(p < 0.05).The inhibition was consistent across all treatments.According to the results,the negative impact of SMX on community structure can result in selection pressure.Furthermore,all of the treatments had drastically improved enzymatic activity by the end of the composting process(day 45).This effect was presumably caused by the deterioration of SMX and a substantial stress reduction.In the last section experiment was performed to compare the influence of inorganic and organic fertilizers on soil physicochemical properties and microbial community structure.The treatment plan comprises of Control and four different fertilizers;(1)Manure,(2)Organic fertilizer,(3)Inorganic fertilizer,and(4)Double organic fertilizer.Two vegetables(Tomato and Cucumber)were selected as a test crop.Soil samples were taken at two different depths(0-20 cm and 20-40cm)and plant samples were collected to calculate yield output.The findings revealed that the soil treated with manure and organic fertilizer increased the yield of vegetables.It was also found that after fertilization and then harvesting of vegetables the abundance of dominant bacterial phyla was reversed.Our findings provided evidence that the stage-specific temperature-based standard composting was still insufficient to control antibiotic resistance.However,it can be concluded that the rebounding of ARGs could be intermitted partially,and more efficient control of antibiotic resistance could be achieved in thermophilic composting compared to conventional methods.A significant effect of composting properties,especially temperature on bacterial community,had a positive effect on ARGs abundances.