| With the rapid development of industry and the improvement of human living standards,various antibiotics have been used and gradually accumulated in the environment,which has led to the emergence of strains carrying antibiotic resistance genes(ARGs).The antibiotics that were effective against them have lost their effectiveness.Antibiotic resistance poses a great threat to human health and ecological environment.The source,transfer and control of antibiotic resistance genes have become the focus of attention.As the two most common antibiotics,tetracycline and ampicillin are widely used in aquaculture and medical treatment,and are generally left in surface water and soil.The final residual antibiotics lead to the devolopment of antibiotic-resistant bacteria.As a kind of clay mineral with wide source,low price,environmental friendliness and stable physical and chemical properties,kaolinite has broad research prospects in microbial friendliness.This article mainly studies the following aspects:1?To understand the impact of low concentration antibiotics on the development of antibiotic resistance,this study examined the expression of ARGs(antibiotic resistance genes)in Escherichia coli(E.coli)after exposure to sub-MIC(minimum inhibitory concentrations)antibiotics for 20 days.In addition,the differential protein profile of the cells before and after exposure to tetracycline was analyzed by iTRAQ(isobaric tags for relative and absolute quantification).The results showed that E.coli developed resistance after 20 days of treatment with 1/2 MIC tetracycline,indicating that low concentrations of tetracycline in the environment would stimulate E.coli to develop antibiotic resistance.The tetracycline resistance genes tetA,tetE and tetZ,?-lactam resistance genes blaTEM and blaFOX,multidrug resistance genes acrA,marA and marR were detected.The protein results indicate that E.coli has a specific energy-saving survival mode under tetracycline stress,and responds to environmental stress by inducing a cell defense and repair system,and exhibits strict regulation of ion transport.The results provide a reference for further analysis of the resistance mechanism of antibiotic stress in the environment.2?This study examined the expression of ARGs in Escherichia coli(E.coli)after exposure to sub-MIC(minimum inhibitory concentration)antibiotics for 15 days in the presence and absence of kaolinite.The results of the real-time polymerase chain reaction(PCR)showed that the expression levels o f the eight target genes of E.coli adhering to kaolinite were relatively decreased,and the MIC results also indicated that the final resistance was lower than that of the strains without kaolinite.A close relationship between E.coli and kaolinite was also revealed,as well as a unique interfacial interaction.In addition,the differential protein expression was further analysed to detect proteins and genes associated with ARGs mutations,and then the underlying mechanisms of cell growth and metabolism were identified under low dose ampicillin stress to elucidate the role of kaolinite in the process.Molecular mechanisms analysis determined that when cells adhering to kaolinite were stressed,transport of ampicillin to the periplasmic space was reduced,a nd the redox metabolism of bacteria was promoted to combat the harsh environment.Moreover,cells synthesised related peptides or proteins under the action of ribosomal proteins to prevent toxic damage.Therefore,this work not only provides new insights into the cellular response to antibiotic stress,but also provides a topic for more research on methods to delay the emergence of ARGs. |
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