Adaptation to Overflow Metabolism by Mutations That Impair tRNA Modification in Experimentally Evolved Bacteria

Area of Science:

• Microbial evolution and adaptation
• Molecular biology and genetics
• Cellular homeostasis and metabolism

Background:

• Essential genes, like tilS, play critical roles in cellular processes.
• tRNA modification enzymes ensure accurate protein translation.
• Microbial adaptation to foreign environments can reveal unexpected genetic adaptations.

Purpose of the Study:

• To identify beneficial mutations in Burkholderia cenocepacia under novel nutritional conditions.
• To investigate the role of the essential gene tilS and its cognate tRNA in microbial adaptation.
• To explore the link between tRNA modification, cellular homeostasis, and growth dynamics.

Main Methods:

• Conducted evolution experiments with Burkholderia cenocepacia in foreign nutritional environments.
• Utilized genetic sequencing to identify mutations in the tilS gene and tRNA^Ile2.
• Performed growth assays and amino acid supplementation experiments to assess fitness advantages.

Main Results:

• Identified multiple independent mutations in tilS and tRNA^Ile2 under strong positive selection.
• Mutant strains exhibited significantly reduced lag phase duration and outcompeted wild-type.
• Mutations decreased tilS enzymatic function but maintained tRNA binding, suggesting a novel role.
• Fitness advantage was specific to rapid growth conditions involving redox imbalance.

Conclusions:

• Disruption of the TilS-tRNA^Ile2 interaction confers a competitive advantage under specific metabolic conditions.
• TilS may have a secondary function beyond tRNA modification, potentially influencing growth timing.
• tRNA-modifying enzymes can play multifaceted roles in sensing metabolic state and maintaining homeostasis.