Influnence Of Erythromycin On Microbial Community Structure And Resisitance Genes In Sediment

In recent years, along with the abuse of antibiotics, the residues in environmental media, has caused wide public concern. The research about the influence on the biological by residual antibiotics in environment, the pollution of resistance genes(Antibiotic Resistance Genes,ARGs) in environmental medium and the influence on biological effects under ARGs increase gradully. Although only trace levels of residual antibiotics in the environment, not enough to kill microorganisms, but long-term exposure of microbes in the environment will be affected, such as the emergence of resistant bacteria. This research on the sediment microbial community structure and the change of resistance genes study under the long-term continuous input of low-concentration erythromycin has got the following conclusions:(1) The constant input of low-concentration erythromycin for a long time has no obvious effect on microbial community diversity, but has a certain extent affect on the microbial community composition. In terms of community composition, sediment microbial community composition involved archaea, bacteria 60 classes and a number of unknown microorganisms. Due to the change of the erythromycin concentration by the constant input and adsorption or biodegradation behavior in the sediment, kinds of microbial abundance changes: a small number of microorganisms present inhibition after the first promoting, most microorganisms showed inhibition at first and then some degree of mitigation, some of the sensitive strain of erythromycin was obviously inhibit at the start of dosing until almost was completely destroyed at the end.(2) The erythromycin resistant bacteria community structure is various in the sediment polluted by long-term low concentration of erythromycin. The results show that there are three erythromycin resistant strains isolated from the sediment, based on its morphological characteristics and 16 S r DNA sequence, were identified as Lysinibacillus sp., Solibacillus silvestris, and Bacillus cereus; further study on the construction of 16 S r DNA clone library, found erythromycin resistant bacterial communities in the sediment can be divided into three groups, namely Uncultured bacterium, Bacilli and C lostridia. Uncultured bacterium holds the largest proportion in the whole library, and the dominant group of the culturable resistant bacteria in the library is Bacil i.(3) The constant input of low-concentration erythromycin for a long time has some extent effect on the exit of ARGs. With the passage of time and erythromycin in the sediment accumulation, species of resistant target almost stable, but the proportion of each type of ARGs in the community will change with low concentrations of erythromycin constant input: the proportion of MLSB and polymyxin resistance genes will rise, the proportion of other kinds of ARGs declines on different degree. For each ARGs: sulfonamides type of ARGs sul1 and sul2 will be to stimulate the gene expression under low-concentration of erythromycin stress, after period of time to adapt to, the expression of genes quantity showed a trend of decline; The expression of beta-lactam type of ARGs won’t affect under the stress of long-time low-concentration of erythromycin; The expression of tetracycline type of ARGs is significantly inhibited along with the continuous input of erythmycin.(4) The constant input of low-concentration erythromycin for a long time makes some originally sensitivity strains to erythromycin have showed certain resistance, which is including pathogens and beneficial bacteria. Under the induction of low-concentration of antibiotics for a long time, on the one hand, pathogenic bacteria acquire resistance and even multiple drug resistance, increasing the difficulty to disease prevention; O n the other hand, some beneficial bacteria in the environment obtain the certain resistance, mak ing it can better play its effect in the environment. In the case of antibiotics pollution problem more and more serious recently, resistant beneficial bacteria applied research, may be an effective solution to solve the problem of antibiotics.