Nov 2, 2014

E. coli populations in unpredictably fluctuating environments evolve to face novel stresses through enhanced efflux activity

BioRxiv : the Preprint Server for Biology
Shraddha KarveSutirth Dey

Abstract

There is considerable understanding about how laboratory populations respond to predictable (constant or deteriorating-environment) selection for single environmental variables like temperature or pH. However, such insights may not apply when selection environments comprise multiple variables that fluctuate unpredictably, as is common in nature. To address this issue, we grew replicate laboratory populations of E. coli in nutrient broth whose pH and concentrations of salt (NaCl) and hydrogen peroxide (H2O2) were randomly changed daily. After ∼170 generations, the fitness of the selected populations had not increased in any of the three selection environments. However, these selected populations had significantly greater fitness in four novel environments which have no known fitness-correlation with tolerance to pH, NaCl or H2O2. Interestingly, contrary to expectations, hypermutators did not evolve. Instead, the selected populations evolved an increased ability for energy dependent efflux activity that might enable them to throw out toxins, including antibiotics, from the cell at a faster rate. This provides an alternate mechanism for how evolvability can evolve in bacteria and potentially lead to broad-spectrum antibiotic resis...Continue Reading

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Mentioned in this Paper

Hydrogen Peroxide
Antibiotic throat preparations
Toxin
Antifungal Antibiotics, Topical
Environment
Nutrients
Public Health Service
Laboratory
Drug Efflux
Antibiotics, Gynecological

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