Adaptive evolution and inherent tolerance to extreme thermal environments

Jennifer Cox, Alyxandria M. Schubert, Michael Travisano, Catherine Putonti

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Background. When introduced to novel environments, the ability for a species to survive and rapidly proliferate corresponds with its adaptive potential. Of the many factors that can yield an environment inhospitable to foreign species, phenotypic response to variation in the thermal climate has been observed within a wide variety of species. Experimental evolution studies using bacteriophage model systems have been able to elucidate mutations, which may correspond with the ability of phage to survive modest increases/decreases in the temperature of their environment. Results. Phage X174 was subjected to both elevated (50°C) and extreme (70°C+) temperatures for anywhere from a few hours to days. While no decline in the phage's fitness was detected when it was exposed to 50°C for a few hours, more extreme temperatures significantly impaired the phage; isolates that survived these heat treatments included the acquisition of several mutations within structural genes. As was expected, long-term treatment of elevated and extreme temperatures, ranging from 50-75°C, reduced the survival rate even more. Isolates which survived the initial treatment at 70°C for 24 or 48 hours exhibited a significantly greater tolerance to subsequent heat treatments. Conclusions. Using the model organism X174, we have been able to study adaptive evolution on the molecular level under extreme thermal changes in the environment, which to-date had yet to be thoroughly examined. Under both acute and extended thermal selection, we were able to observe mutations that occurred in response to excessive external pressures independent of concurrently evolving hosts. Even though its host cannot tolerate extreme temperatures such as the ones tested here, this study confirms that X174 is capable of survival.

Original languageEnglish (US)
Article number75
JournalBMC evolutionary biology
Issue number1
StatePublished - 2010

Bibliographical note

Funding Information:
This work was partially supported by the Loyola University Chicago WISER fellowship (JC) and through the NSF REU in Bioinformatics program at Loyola University Chicago (AS). MT is supported by the NSF. We thank Mr Kamil Cygan for his assistance in resequencing several of the strains.


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