Adaptive genetics reveals constraints on protein structure/function by evolving E. coli under constant nutrient...

Area of Science:

• Microbiology
• Evolutionary Biology
• Genomics

Background:

• Microbial evolution under laboratory selection generates genetic diversity through mutations and competition.
• Whole-genome sequencing enables identification of adaptive mutations and mapping of gene structure-function relationships.
• Adaptive genetics leverages these capabilities to study adaptation in evolving microbial populations.

Purpose of the Study:

• To discover targets of selection and their mutational consequences in E. coli during chronic nutrient limitation.
• To apply adaptive genetics to identify genes and specific residues under selection pressure.
• To map gene structure-function relationships in evolving microbial systems.

Main Methods:

• Culturing replicate E. coli populations for over 300 generations in glucose-limited chemostats.
• Performing whole-genome, whole-population sequencing every 50 generations at 1000X coverage.
• Identifying mutations reaching at least 1% frequency to pinpoint targets of selection.

Main Results:

• Identified 39 high-value genes frequently mutated, far exceeding chance expectation.
• A majority of these genes encode regulatory proteins controlling gene expression at multiple levels.
• Recurrent mutations cluster at sites involved in RNA-protein or protein-protein interactions, affecting both regulatory and structural genes.

Conclusions:

• Experimental evolution coupled with sequencing validates inferences from traditional molecular genetics.
• Adaptive genetics effectively identifies genes conferring selective advantages and specific residues involved in adaptation.
• This approach provides insights into the 'why' and 'how' of specific selective advantages conferred by mutations.