| In recent years,antibiotic resistance genes?ARGs?and their harm have attracted widespread attention.The research results of environmental area showed the pollution level of ARGs was heavy in environmental mediums.The ocean is the final emission site for human pollutants.It receives a large number of pollutants including ARGs every day.The long-distance transport capability of the ocean can promote the spread of ARGs.However,there are only a few studies reporting the pollution level of ARGs in ocean.This study investigated the pollution level of antibiotic resistance genes?ARGs?in coastal area,and distinguished the main pollution sources of ARGs in coastal area.Moreover,this study investigated the influence of terrestrial ARGs to corresponding ARGs in coastal area,analyzed the reasons causing that variation.The main content and conclusions of this study are:?1?Sample sites belonged to different areas of coastal area were set in this study,and the common ARGs and The pollution levels of antibiotics and drug resistance genes varied widely among different types of areas.The concentration of antibiotics and ARGs in marine aquaculture and sewage rivers estuary were high,while the concentration of antibiotics and drug resistance genes in the background and tourist areas were low.The abundance and detection rate of sulfonamide-ARGswere found the highest in all investigated ARGs(the average abundance of sul1 and sul2 was 2.38×10-3/16S copies and 1.7×10-3/16S copies,respectively).Besides sulfonamide-ARGs,both the abundance of ermB(average abundance was 6.63×10-4/16S copies)and tetM(average abundance was 3.07×10-4/16S copies)were high,too.The correlation of int1and ARGs was analyzed in this study,and the results showed int1 had strong relationship with both sul1andsul2,which indicated that int1 might promote the diffusion of ARGs in marine environment.?2?Seawater/freshwater mixed microcosms were established to simulate various regions of coastal areas,and the abundance of ARGs and community structures variation were determined in certain time.The results showed the variation pattern of ARGs were different each other,while the abundance were stable finally.The effect of salinity on terrestrial ARGs was analyzed in this study,and the results showed salinity had little affection to terrestrial ARGs in most cases.However,the abundance of tetM was obviously elevated in high salinity microcosms comparing that in low salinity microcosms.Bacterial community structures in mixed microcosms were analyzed in this study,and the results showed the bacterial community structures in different microcosms showed huge difference.The abundance of dominant bacteria in seawater and freshwater microcosm decreased dramatically.It is need to mention that some marine indigenous bacteria seemed could be neglected in seawater due to the content of these bacteria is low.However,the content of these bacteria increased in mixed microcosms as some microelements in freshwater could accelerated the growth of these bacteria.Moreover,the content of some host of ARGs could also increase,and may lead to the increase of human health risk in coastal area.?3?Freshwater bacteria-seawater bacteria Conjugation transfer systems were established to assess the transfer possibility of ARGs between freshwater bacteria and seawater bacteria,and the influence of salinity to the transfer frequency were evaluated.The results showed ARGs could transfer between fresh bacteria and seawater bacteria.Moreover,salinity could not obviously affect the efficiency of the transfer,which indicated that the ARGs risk caused by coastal sewage discharge might larger than expected.The growth curves of both freshwater and seawater in different salinity condition were investigated in this study,and the result showed salinity could influence the growth status of both the bacteria.The conclusions of this study could help to understand the pollution status of ARGs and clarify the diffusion of ARGs in the environment,and provide technical assistance for the control of ARGs pollution. |
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