A consortium-based approach to adaptive laboratory evolution of Acinetobacter baylyi ADP1 reveals novel genetic...

This study focuses on a novel process for the adaptive laboratory evolution (ALE) of Acinetobacter baylyi ADP1 to enable simultaneous utilization of multiple lignin-related aromatics (LRAs). The genomes of the evolved strains were sequenced and compared with the wild type for identification of genetic targets for reverse engineering.

In the first step of the two-step ALE process, different A. baylyi ADP1 strains were evolved to grow on high concentrations of individual LRAs. In the second step, a consortium of these single-LRA evolved strains were grown and further evolved on a mixture of LRAs, which resulted in a unique strain (A. baylyi SAG_185). Whole-genome sequence (WGS) analysis of all the evolved strains revealed large-scale mutations involving insertion sequences.

Acinetobacter baylyi SAG_185 could simultaneously utilize multiple LRAs at higher concentrations (85 mmol l-1) as well as grow on depolymerized lignin. WGS analysis of the evolved strains obtained from ALE revealed potential genetic targets for reverse engineering of A. baylyi ADP1 for lignin valorization. In particular, A. baylyi SAG_185 revealed a critical mutation in the vanR repressor gene, resulting in the up-regulation of vanAB genes which are required to convert vanillate to the key intermediate, protocatechuate.