| The use of antibiotics is a common phenomenon in my country’s aquaculture industry.At present,the research on the use of antibiotics in traditional aquaculture models is relatively complete.However,for the emerging farming mode of biofloc technology(BFT),there are few reports on the impact of antibiotic use on it.Bioflocs are mainly bacterial clusters formed by the flocculation of a large number of microorganisms,feed fecal residues,organic debris and some polymers in the water body through complex interactions.The use of antibiotics undoubtedly increases the stress response of the microbial community and exerts strong selective pressure on the microbial community,resulting in an impact on the structure and composition of the microbial community.So for this kind of microbial content and closed breeding mode,when antibiotics need to be used in the breeding process,the research on the impact of these antibiotics on biological flocs is particularly critical.The effects of different types and doses of antibiotics on the water quality treatment of the bioflocculation aquaculture system,the situation of drug residues in the system,and the accumulation of antibiotic resistance genes after drug use are all issues that need to be improved and supplemented by research.In this study,the antibiotic resistance genes contained in the bioflocs in the farm were detected by metagenomics,and the effects of different types of antibiotics on the ammonia nitrogen conversion capacity of the bioflocs during the expansion stage and the effect of neomycin sulfate on the bioflocs were studied.The effect of ammonia nitrogen conversion ability,heterotrophic bacteria number and accumulation of antibiotic resistance genes in the colony.1.Effects of resistance gene types in bioflocs and four commonly used antibiotics on inoculation culture of bioflocsIn this experiment,the types of resistance genes in bioflocs were investigated through metagenomics,and the effects of four commonly used antibiotics(enrofloxacin,doxycycline hydrochloride,neomycin sulfate and sulfamonomethoxine)on bioflocs were studied.Expansion effects.A total of 80 different types of antibiotic resistance genes,46 single antibiotic resistance genes and 34 multi-antibiotic resistance genes were detected in the flocs.Actinobacteria,Bacteroidetes and Proteobacteria accounted for 33%,27% and 26% of the bacterial community,respectively.Flavobacterium,Pseudomonas,Owenweeksia,Auromonas and Rheinheimer are the dominant genera.In this experiment,four different types of antibiotics,namely enrofloxacin,doxycycline hydrochloride,neomycin sulfate and sulfamethoxazole,were selected.The experimental groups were divided into 5 groups.Group added 1.6g doxycycline hydrochloride,group C added 0.964 g sulfamethoxazole,group D added 0.4g neomycin sulfate,group E did not add any antibiotics(the concentration of antibiotics in each group was 10 mg/L).In terms of ammonia nitrogen conversion,groups A and D have great changes,and the ammonia nitrogen concentration has increased significantly after the addition of antibiotics.Due to the addition of antibiotics,the flora in the biofloc is inactivated,releasing a large amount of ammonia nitrogen and after a long period of time.reduced to low levels.The four antibiotics had little effect on nitrite in the water,but had a certain effect on the accumulation of nitrate.At the end of the expansion experiment,the antibiotics had inhibitory effects on the accumulation of nitrate in each group,especially in groups A and D.After the expansion experiment,the number of heterotrophic bacterial communities in the five experimental groups and the initial water samples was quite different.The number of heterotrophic bacterial communities in the five experimental groups was group C > group A > group D > group B > group E.2.Effects of different concentrations of neomycin sulfate on ammonia nitrogen conversion rate and resistance genes of biological flocsIn this experiment,the effect of neomycin sulfate on the effect of neomycin sulfate on the treatment of ammonia nitrogen and antibiotic resistance genes in biological flocs was investigated.The gene content was tested.In terms of the rate of ammonia nitrogen conversion,the first continuous monitoring showed that the ammonia nitrogen removal rates of the four groups were 3.88±0.02 mg TAN/g TSS·h,2.22±0.03 mg TAN/g TSS·h,2.17±0.04 mg TAN/h,respectively.g TSS·h and 1.72±0.02 mg TAN/g TSS·h,ammonia nitrogen removal rate group A > group B > group C > group D.The second continuous monitoring showed that the ammonia nitrogen removal rates of the four groups were 2.99±0.08 mg TAN/g TSS·h,2.98±0.03 mg TAN/g TSS·h,2.97±0.08 mg TAN/g TSS·h,and 5.10 ±0.03 mg TAN/g TSS·h,ammonia nitrogen removal rate D group>A group>B group>C group.It can be found that as the concentration of neomycin sulfate increases during the first dosing,the effect on the conversion rate of ammonia nitrogen is greater.However,after the flocs developed resistance,the added concentration of neomycin sulfate had no negative effect on the conversion rate of ammonia nitrogen,and even a high concentration of neomycin sulfate could promote the conversion of ammonia nitrogen in biological flocs.Antibiotic testing of water bodies found that both tests failed to detect the presence of neomycin sulfate in water bodies.The detection of antibiotic resistance genes found that neomycin sulfate had a greater effect on the four genes aph(3’)-Ia,aph(3’)-IIa,aac(6’)-Ib,aac(3)-II.The ability to select and enrich,and the gene copy number increased exponentially with increasing neomycin sulfate concentration.However,group B added with a lower concentration of neomycin sulfate showed opposite results to groups C and D,and the copy numbers of the six antibiotic resistance genes were the lowest.After the experiment,the number of heterotrophic bacterial colonies in the four experimental groups was detected,and it was found that the number of bacterial colonies in group B was significantly increased compared with the other three groups,from 8.10×106 CFU/ml in the initial water sample to 35× 106 CFU/ml,while the remaining three groups only rose to the range of 20.00×106 CFU/ml to 21.00×106 CFU/ml.3.The effect of long-term use of high concentration of neomycin sulfate on biological flocsThis experiment explored the effect of long-term use of high concentration of neomycin sulfate on biological flocs and the effect of ozone on the removal of antibiotic resistance genes.Group A did not add antibiotics,the initial neomycin sulfate concentration in group B was 2.00 mg/L,the initial neomycin sulfate concentration in group C was 4.00 mg/L,and the initial neomycin sulfate concentration in group D was 6.00 mg/L.The continuous monitoring results of the first dosing showed that the ammonia nitrogen removal rates of the four groups were 1.99±0.02 mg TAN/g TSS·h,0.74±0.03 mg TAN/g TSS·h,and 0.69±0.02 mg TAN/g TSS·h,respectively.and 0.58±0.03 mg TAN/g TSS·h,the high concentration of neomycin sulfate had a great influence on the ammonia nitrogen conversion rate of biological flocs.The results of the first continuous monitoring without drug addition showed that even under long-term incubation with high concentrations of antibiotics,the removal rates of ammonia nitrogen in the four groups were 1.77±0.07 mg TAN/g TSS·h,1.75±0.08 mg TAN/g,respectively.TSS·h,2.36±0.02 mg TAN/g TSS·h and 2.26±0.07 mg TAN/g TSS·h,ammonia nitrogen removal rate group C > group D > group A > group B.And there was a phenomenon that the ammonia nitrogen conversion rate of groups C and D added with high concentration of neomycin sulfate was significantly improved compared with the ammonia nitrogen conversion rate of group A.The results of continuous monitoring of the second dosing showed that the ammonia nitrogen removal rates of the four groups were 1.76±0.02 mg TAN/g TSS·h,1.47±0.02 mg TAN/g TSS·h,and 2.03±0.03 mg TAN/g TSS·h,respectively.h and 1.80±0.02 mg TAN/g TSS·h,ammonia nitrogen removal rate in group C > group D > group A > group B.The ammonia nitrogen turnover rate in group D decreased,from 2.26 ± 0.07 mg TAN/g TSS h to 1.80 ± 0.02 mg TAN/g TSS h,indicating that the addition of high concentrations of neomycin sulfate was resistant to the The biological flocs still have some influence.After the experiment,the number of heterotrophic bacterial colonies in the four experimental groups was detected,and it was found that the number of bacterial colonies in groups B,C and D was significantly higher than that in group A,which may be due to the long-term high concentration of antibiotics.The role of cluster selection and enrichment. |
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