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K-State Today

March 9, 2017

Division of Biology Seminar March 10

By Division of Biology


Eva Top, professor and director in the biological sciences department from the University of Idaho, will present "Compensatory mutations improve general permissiveness to antibiotic resistance plasmids" as part of the Division of Biology Seminar Series at 4 p.m. Friday, March 10, in 221 Ackert Hall.

The lecture will cover horizontal gene transfer mediated by broad-host-range plasmids, which are an important mechanism of antibiotic resistance spread. While not all bacteria maintain plasmids equally well, plasmid persistence can improve over time, but general evolutionary mechanisms have not yet emerged. Top's goal was to identify these mechanisms, and to assess if adaptation to one plasmid affects the permissiveness to others. Top's lab experimentally evolved Pseudomonas sp. H2 containing multi-drug resistance plasmid RP4, determined plasmid persistence and cost using a joint experimental-modeling approach, resequenced evolved clones, and reconstructed key mutations. Plasmid persistence improved in fewer than 600 generations because the fitness cost turned into a benefit. Improved retention of naive plasmids indicated that the host evolved toward increased plasmid permissiveness. Key chromosomal mutations affected two accessory helicases and the RNA polymerase -subunit. Top and other findings suggest that poor persistence of an antibiotic resistance plasmid can be caused by a high cost of helicase-plasmid interactions that can be rapidly ameliorated by compensatory mutations. These mutations may threaten the efficacy of traditional antibiotic treatments even more than single drug resistance mutations, as adaptation of a pathogen to one plasmid can result in improved retention of other plasmid-encoded antibiotic resistance.

If you would like to visit with Top, please contact Tom Platt at tgplatt@k-state.edu

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