Release and Constancy of an Antibiotic Resistance Gene in Seawater under Grazing Stress by Ciliates and Heterotrophic Nanoflagellates

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    • Bien Thi Lan Thanh
    • Center for Marine Environmental Studies, Ehime University|The United Graduate School of Agricultural Sciences, Ehime University|Department of Biotechnology, Nong Lam University
    • Thao Ngo Vy
    • Center for Marine Environmental Studies, Ehime University|Faculty of Environment and Resources, Nong Lam University


<p>Extracellular DNA (exDNA) is released from bacterial cells through various processes. The antibiotic resistance genes (ARGs) coded on exDNA may be horizontally transferred among bacterial communities by natural transformation. We quantitated the released/leaked tetracycline resistance gene, <i>tet</i>(M) over time under grazing stress by ciliates and heterotrophic nanoflagellates (HNFs), and found that extracellular <i>tet</i>(M) (ex-tetM) increased with bacterial grazing. Separate microcosms containing <i>tet</i>(M)-possessing bacteria with ciliates or HNFs were prepared. The copy number of ex-tetM in seawater in the ciliate microcosm rapidly increased until 3 d after the incubation, whereas that in the HNF microcosm showed a slower increase until 20 d. The copy number of ex-tetM was stable in both cases throughout the incubation period, suggesting that extracellular ARGs are preserved in the environment, even in the presence of grazers. Additionally, ARGs in bacterial cells were constant in the presence of grazers. These results suggest that ARGs are not rapidly extinguished in a marine environment under grazing stress.</p>


  • Microbes and Environments

    Microbes and Environments 32(2), 174-179, 2017

    Japanese Society of Microbial Ecology · The Japanese Society of Soil Microbiology


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