Study On Toxicity And Mechanism Of Environmental Antibiotics Inhibited Soil Urease

Antibiotics is a world-wide health threat to human beings due to their increasing content in soil distribution systems.Since entering the soil environment,antibiotics could destroy the stable state of the original soil environment,affect the biological activity of soil urease,break the balance of soil urease in the circulation of soil carbon,nitrogen as well as phosphorus,and then pose a serious threat to soil function and human health.At present,the toxicity of antibiotics to soil has been widely discussed,however,the problem of antibiotic toxicity to soil urease activity is still lack of systematic research,and the molecular toxicity mechanism of antibiotics on soil urease has not been elucidated,which restricts the essential evaluation of the contamination mechanism of antibiotics on soil urease.Therefore,research on the biotoxicity difference and toxicity mechanism of antibiotics has become an urgent environment problem to be solved.In the present work,the fluorescence quenching types and structure characteristics of antibiotics and soil urease conjugates were analyzed by molecular toxicity experiment,fluorescence spectroscopy and molecular docking simulation.The theoretical data were compared with the of toxicity test.The toxicity mechanism of toxin to soil urease was further analyzed by using the molecular dock simulation.The specific work is as follows:?1?Study on toxicity and mechanism of environmental antibiotics inhibited soil urease.In this study,the effects of six kinds of antibiotics on soil urease activity were studied by molecular toxicity experiment.Except for ciprofloxacin,there was no significant effect on soil urease activity,quinolone antibiotics?norfloxacin,ofloxacin and enrofloxacin?and?-lactam antibiotics?penicillin,amoxicillin and cefalexin?inhibited soil urease activity.Tetracycline antibiotics?tetracycline,oxytetracycline and doxycycline?promoted the soil urease activity.In addition to azithromycin,it promoted soil urease activity,macrolide antibiotics?erythromycin,clarithromycin and erythromycin?,aminoglycoside antibiotics?kanamycin,tobramycin and gentamicin?and sulfonamides antibiotics?sulfadiazine,sulfamethazine and sulfathiazole?effect on soil urease activity performance were not obvious.?2?Study on toxicity and mechanism of environmental antibiotics inhibited soil urease.In this study,the quenching types of the interaction between six antibiotics and soil urease were inferred by using fluorescence spectroscopy and molecular toxicity data.Four quinolone antibiotics?ciprofloxacin,norfloxacin,ofloxacin,enoxacin?and three?-lactam antibiotics?penicillin,cefalexin,amoxicillin?showed static quenches in the catalytic activity center of soil urease.Three tetracycline antibiotics?tetracycline,oxytetracycline and doxycycline?showed static quenches in the non-catalytic activity center of soil urease.Three macrolide antibiotics?azithromycin,erythromycin,clarithromycinanderythromycin?,three aminoglycoside antibiotics?kanamycin,tobramycin and gentamicin?and three sulfonamides antibiotics?sulfadiazine,sulfamethazine and sulfathiazole?showed static quenches or dynamic quenches in the non-catalytic activity center of soil urease.?3?Study on toxicity and mechanism of environmental antibiotics inhibited soil urease.In this study,antibiotics-urease was obtained by the MOE molecular docking.According to the cognition of urease on the interaction site of antibiotics,the activity of antibiotics inhibitory urease can vary with the energy,binding area,hydrogen bond,ionic bonds and so on.The results of MOE molecular dock simulation results showed as follow:?1?Quinolone antibiotics combined with catalytic activity center of soil urease thus inhibited soil urease activity.The total binding area of ligand and the whole energy of quinolone antibiotics on soil were urease positively related with toxicant toxicity.Hydrogen bond such as O²⁵?Lys₄₄₃,C⁶?Glu₃₆₉ and the ionic bond such as N⁴-Asp₇₉,O²⁵-Lys₄₄₃43 were positively related with the toxins'toxicity.Hydrogen bond such as O²³?Lys₄₄₃,N⁴?Asp₁₀₃ and ionic bond such as N⁴-Glu₅₀₃₃ were negatively related with the toxins'toxicity.The hydrogen bond and ionic bond formed by ciprofloxacin and soil urease have little correlation with the toxins'toxicity.Besides,the two Ni²⁺ionic in the catalytic activity centers had no significant effect on the binding process.?2??-lactam antibiotics combined with catalytic activity center of soil urease and inhibited soil urease activity.The total binding area of ligand and the whole energy of?-lactam antibiotics on soil urease were positively related with toxicant toxicity.Hydrogen bond such as O⁶³?Lys₄₄₃,O⁸?Asn₄₆ and the ionic bond such as O¹³-Arg₉₄,O¹³-Arg₅₂2 were positively related with the toxins'toxicity.Hydrogen bond such as S⁴?Gly₃₆₈,O¹⁸?Asp₇₉ and the ionic bond such as O⁶²-Lys₁₂₄,O⁶³-Arg₅₁₈ were negatively related with the toxins'toxicity.Besides the two Ni²⁺ionic in the catalytic activity centers had no significant effect on the binding process.?3?Tetracycline antibiotics combined with non-catalytic activity center of soil urease and Indirectly promoted soil urease activity.The total binding area of ligand and the whole energy of tetracycline antibiotics on soil urease were positively related with toxicant toxicity.Hydrogen bond such as O³?Phe₅₆₇,N²¹?Phe₅₆₇ and the ionic bond such as N⁴-Glu₃₁₁,N⁴-Phe₅₆₇67 were positively related with the toxins'toxicity.Hydrogen bond such as C⁴?Glu₃₁₁,O¹?Arg₃₇₃ and the ionic bond of N⁴-Asp₇₉9 were negatively related with the toxins'toxicity.?4?Compounds formed by combining aminoglycosides,macrocyclic amides and sulfonamides in the non-catalytically active center of soil urease have no significant effect on soil urease activity?azithromycin is an exception?.The interaction effect between aminoglycosides antibiotics,sulfonamide antibiotics,macrolide antibiotics and soil urease on the total binding area,whole energy,hydrogen bond,ionic bond were no related with the toxins'toxicity.Besides,regarding azithromycin,the hydrogen bond of O^4B?Asp₃₂₉,O¹³?Asp₃₉₄,C^8A?Glu₅,O^2A?Glu₅ and the ionic bond of N¹-Glu₄₅,N¹-Asp₂₅₈ have a certain correlation with toxins'toxicity.