Authors:

Anja Hofmeier

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About Paper:

Antibiotic resistance inhibits the treatment of bacterial infections. Approximately 23,000 patients in the United States die each year due to antibiotic resistance, resulting in increased healthcare costs of over $20 billion [1]. Bacterial infections become increasingly difficult to treat as bacteria acquire beneficial mutations and evolve resistance to antimicrobial treatments. Therefore, to effectively utilize antibiotics, it is crucial to understand how common environmental characteristics, such as nutrient availability, affect the evolution of antibiotic resistance. We investigated the effect of nutrient limitation dn the evolution of antibiotic resistance in Escherichia coli. We evolved E. coli for 24 days in nitrogen- or carbon-limited environments with and without tobramycin. Nitrogen-limited populations were less likely than carbon-limited populations to survive antibiotic treatment. We competed the evolved populations against the ancestor in their respective nutrient-limited environment with and without tobramycin. As expected, evolved populations were more fit than the ancestor when competed in their evolutionary environment. Surprisingly, our nitrogen-limited populations that evolved without tobramycin had an even larger fitness advantage when tobramycin was added, despite not having evolved in that environment. This trend was unique to nitrogen-limited populations and was not seen under carbon limitation. Our results suggest that carbon and nitrogen limitation had different pleiotropic effects on the evolution of tobramycin resistance. We saw an unexpected relationship between acquiring resistance to tobramycin and evolving under nitrogen limitation: When evolved with tobramycin, nitrogen-limited populations were less likely to survive; however, when evolved in the absence of tobramycin, the populations acquired greater fitness in environments with antibiotics. Our research suggests that adaptation to environmental conditions such as nutrient limitation could facilitate the evolution of tobramycin resistance.

Source:

Loyola University Chicago

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Co-authors:

Anja Hofmeier