Bacterivorous Ciliate <i>Tetrahymena pyriformis</i> Facilitates <i>vanA</i> Antibiotic Resistance Gene Transfer in <i>Enterococcus faecalis</i>
<b>Background:</b> Wastewater treatment plants (WWTPs) are hotspots for the emergence and spread of antibiotic resistance genes (ARGs). In activated sludge treatment systems, bacterivorous protozoa play a crucial role in biological processes, yet their impact on the horizontal gene trans...
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| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
MDPI AG
2025-04-01
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| Series: | Antibiotics |
| Subjects: | |
| Online Access: | https://www.mdpi.com/2079-6382/14/5/448 |
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| Summary: | <b>Background:</b> Wastewater treatment plants (WWTPs) are hotspots for the emergence and spread of antibiotic resistance genes (ARGs). In activated sludge treatment systems, bacterivorous protozoa play a crucial role in biological processes, yet their impact on the horizontal gene transfer in Gram-positive enteric bacteria remains largely unexplored. This study investigated whether the ciliate <i>Tetrahymena pyriformis</i> facilitates the transfer of antibiotic resistance genes between <i>Enterococcus faecalis</i> strains. <b>Methods</b>: Conjugation assays were conducted under laboratory conditions using a <i>vanA</i>-carrying donor and a rifampicin-resistant recipient at an initial bacterial concentration of 10<sup>9</sup> CFU/mL and ciliate density of 10<sup>5</sup> N/mL. <b>Results</b>: Transconjugant numbers peaked at 2 h when experiments started with recipient bacteria harvested in the exponential growth phase, and at 24 h when bacteria were in the stationary phase. In both cases, <i>vanA</i> gene transfer frequency was highest at 24 h (10<sup>−4</sup>–10<sup>−5</sup> CFU/mL), and the presence of energy sources increased gene transfer frequency by one order of magnitude. <b>Conclusions</b>: These findings suggest that ciliate grazing may contribute to <i>vanA</i> gene transfer in WWTP effluents, potentially facilitating its dissemination among permissive bacteria. Given the ecological and public health risks associated with <i>vanA</i> gene persistence in wastewater systems, understanding protozoan-mediated gene transfer is crucial for mitigating the spread of antibiotic resistance in aquatic environments. |
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| ISSN: | 2079-6382 |