Objectives:Understanding how phenotypic traits vary has been a longstanding goal of evolutionary biologists. When examining antibiotic-resistance in bacteria, it is generally understood that the minimum inhibitory concentration (MIC) has minimal variation specific to each bacterial strain-antibiotic combination. However, there is a less studied resistance trait, the mutant prevention concentration (MPC), which measures the MIC of the most resistant sub-population. Whether and how MPC varies has been poorly understood. Here, we ask a simple, yet important question: How much does the MPC vary, within a single strain-antibiotic association? Using a Staphylococcus species and five antibiotics from five different antibiotic classes—ciprofloxacin, doxycycline, gentamicin, nitrofurantoin, and oxacillin—we examined the frequency of resistance for a wide range of concentrations per antibiotic, and measured the repeatability of the MPC, the lowest amount of antibiotic that would ensure no surviving cells in a 1010 population of bacteria.Results: We found a wide variation within the MPC and distributions that were rarely normal. When antibiotic resistance evolved, the distribution of the MPC changed, with all distributions becoming wider and some multi-modal.Conclusion: Unlike the MIC, there is high variability in the MPC for a given bacterial strain-antibiotic combination.

In bacteria, evolution of resistance to one antibiotic is frequently associated with increased resistance (cross‐resistance) or increased susceptibility (collateral sensitivity) to other antibiotics. Cross‐resistance and collateral sensitivity are typically evaluated at the minimum inhibitory concentration (MIC). However, these susceptibility changes are not well characterized with respect to the mutant prevention concentration (MPC), the antibiotic concentration that prevents a single‐step mutation from occurring. We measured the MIC and the MPC for Staphylococcus epidermidis and 14 single‐drug resistant strains against seven antibiotics. We found that the MIC and the MPC were positively correlated but that this correlation weakened if cross‐resistance did not evolve. If any type of resistance did evolve, the range of concentrations between the MIC and the MPC tended to shift right and widen. Similar patterns of cross‐resistance and collateral sensitivity were observed at the MIC and MPC levels, though more symmetry was observed at the MIC level. Whole‐genome sequencing revealed mutations in both known‐target and nontarget genes. Moving forward, examining both the MIC and the MPC may lead to better predictions of evolutionary trajectories in antibiotic‐resistant bacteria.

Ecological and evolutionary processes govern the fitness, propagation, and interactions of organisms through space and time, and viruses are no exception. While COVID-19 research has primarily emphasized virological, clinical, and epidemiological perspectives, crucial aspects of the pandemic are fundamentally ecological or evolutionary. Here, we highlight five conceptual domains of ecology and evolution – invasion, consumer-resource interactions, spatial ecology, diversity, and adaptation – that illuminate (sometimes unexpectedly) the emergence and spread of SARS-CoV-2. We describe the applications of these concepts across levels of biological organization and spatial scales, including within individual hosts, host populations, and multi-species communities. Together, these perspectives illustrate the integrative power of ecological and evolutionary ideas and highlight the benefits of interdisciplinary thinking for understanding emerging viruses.

This study looked for the presence of environmental antibiotic resistance genes and their capacity to disseminate through conjugation. Water and soil samples were collected from pristine zones of the Ecuadorian Amazon Basin (Sucumbíos, Napo and Orellana provinces), and they were inoculated in a modify wheat grain medium (WGM). Some of WGM cultures contained diverse bacterial species that were able to transfer antibiotic resistance genes to Escherichia coli K12. Finally, 10 strains were isolated and proved to be responsible of antibiotic resistance gene transfer. Strains were identified (using 16S rDNA sequences) as Serratia sp., Pseudomonas sp., Listonella sp., and Aeromonas sp. In this work, we proved that environmental bacteria can transfer antibiotic resistance genes as tetraciclin and ampicilin.Keywords. Conjugation, horizontal gen transfer, antibiotic resistance genes, environmental bacteria. ResumenEl presente estudio exploró la presencia y la capacidad de diseminación de genes de resistencia a antibióticos provenientes de bacterias ambientales. Se recolectó muestras de agua y suelo de zonas prístinas de la Amazonía ecuatoriana (provincias de Sucumbíos, Napo y Orellana) las cuales fueron inoculadas en un medio de grano de trigo modificado (WGM). Algunos de estos cultivos multi-bacterianos (mixtos) demostraron tener bacterias capaces de transferir genes de resistencia a antibióticos a una cepa de Escherichia coli K12. A partir de los cultivos mixtos se aisló 10 cepas bacterianas responsables de esta transferencia. Las cepas aisladas fueron identificadas mediante el secuenciamiento del gen del ARN ribosomal 16S (16S rDNA) como Serratia sp., Pseudomonas sp., Listonella sp. y Aeromonas sp. El hallazgo más importante del presente trabajo fue el probar que existe transferencia de genes que proveen resistencia a antibióticos como la tetraciclina y ampicilina a partir de bacterias ambientales.Palabras Clave. Conjugación, transferencia horizontal de genes, genes de resistencia a antibióticos, bacterias ambientales. IntroducciónLa existencia de una amplia diversidad de bacterias resistentes a antibióticos ha sido relacionada con el uso masivo de estos fármacos en el tratamiento de infecciones y en prácticas de ganadería. Sin embargo, los genes de resistencia a antibióticos están presentes en bacterias que pululan en ríos y suelos de zonas remotas, lejanas a la actividad humana. Más aún, el medio ambiente probablemente fue el escenario natural donde se originaron y evolucionaron estos genes [1]. Existe evidencia de que estos genes han evolucionado y se han diversificado antes de la llamada era de los antibióti-cos [2]. Los antibióticos por lo general son producidos por miembros de comunidades microbianas ambientales complejas, muchos antibióticos actúan como un medio de comunicación química entre bacterias. Otros antibió-ticos sirven para eliminar la competencia por nutrientes. Las bacterias del suelo y de los ríos han estado expuestas a antibióticos por miles de millones de años y han evolucionado genes que ...