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

Abstract

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, tet(M) over time under grazing stress by ciliates and heterotrophic nanoflagellates (HNFs), and found that extracellular tet(M) (ex-tetM) increased with bacterial grazing. Separate microcosms containing tet(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.

1419 - Low antibiotic concentrations and resistance in microbial communities

“…This effect of predation has been independently hypothesized by another research group 166 and, subsequent to our study, a similar outcome was reported by Bien and colleagues for a different conjugative ARG plasmid under grazing by taxonomically and physiologically diverse protozoa. 199 Higher metabolic activity of bacteria under predation has also been demonstrated in the laboratory, supporting the mechanistic hypothesis. 200 Furthermore, the conjugation-promoting effect of ciliates has been shown to be strong enough to reverse near-loss of the plasmid following exposure to the conjugative plasmid dependent bacteriophage PRD1.…”

“…An alternative mechanism by which predation can facilitate HGT of ARGs is through the release of DNA from consumed cells to the environment, where it can be acquired by bacteria through natural transformation. 199,201 We also tested for the effect of protozoan predation, structured environment and low kanamycin concentration (approx. 6 % of mean MIC value of strains) on the transfer of the RP4 plasmid from one donor strain in a 62-strain artificial bacterial community over 40 days (IV).…”

Temporal variation of eukaryotic community structures in UASB reactor treating domestic sewage as revealed by 18S rRNA gene sequencing

“…Furthermore, most fungi are difficult to identify by microscopic observation. Recently, instead of by microscopic observation, molecular biological techniques such as clone libraries 9 , quantitative real-time PCR 10 , fluorescence in situ hybridization 11 , and high-throughput sequencing techniques 12 have been applied to analyze a greater diversity of eukaryotes in wastewater treatment systems and other enrivonments (e.g. lake and marine).…”

Tetracycline Resistance Gene Profiles in Red Seabream (Pagrus major) Intestine and Rearing Water After Oxytetracycline Administration

“…tet (M) and tet (S), which are ribosomal protection protein (RPP) genes, appear to have diverged from the elongation factor-encoding genes in the distant past ( Kobayashi et al, 2007 ), and tet (M) is known to be the most widely detected tet ( Roberts et al, 2012 ). Plasmid-borne RPP genes are expected to have become widely distributed in the environmental communities due to their greater stability ( Bien et al, 2015 , 2017 ). Fish samples showed distinct tet profiles that changed with time.…”