EVOLUTIONARY ADAPTATION TO TEMPERATURE. V. ADAPTIVE MECHANISMS AND CORRELATED RESPONSES IN EXPERIMENTAL LINES OF...

Area of Science:

• Microbial evolution
• Bacterial adaptation
• Genetics and genomics

Background:

• Experimental evolution studies demonstrate temperature-specific genetic adaptation in Escherichia coli.
• Populations were propagated for 2000 generations under constant and fluctuating thermal regimes with glucose as the sole carbon source.

Purpose of the Study:

• To investigate the physiological mechanisms underlying temperature-specific adaptation in Escherichia coli.
• To determine if changes in glucose transport are responsible for evolved fitness differences across thermal regimes.
• To assess the consistency of adaptive mechanisms among replicate lines within and across different thermal environments.

Main Methods:

• Compared direct fitness responses to glucose with correlated fitness responses to maltose in evolved Escherichia coli lines.
• Analyzed fitness differences in glucose and maltose to infer changes in glucose transport pathways.
• Evaluated heterogeneity in correlated responses to identify diverse underlying adaptive mechanisms.

Main Results:

• Most evolved lines exhibited significantly different fitness on glucose versus maltose, supporting a role for altered glucose transport.
• Evidence suggests adaptation primarily involved changes in glucose transport, not random decay of maltose transport.
• Significant heterogeneity in correlated responses among replicate lines indicates multiple distinct mechanisms for temperature-specific adaptation.

Conclusions:

• Temperature-specific adaptation in Escherichia coli frequently involves modifications to glucose transport systems.
• Evolutionary pathways for adaptation to thermal stress are diverse, even among replicate populations under identical conditions.
• Observed heterogeneity in adaptive mechanisms provides a reservoir of genetic variation for future environmental adaptation.