@article{Pan2026, 
author = {Saifu Pan and Xiaojie Wang and Jingjing He and Nan Peng},
title = {RecN: A tunable switch for DNA repair choice and stress tolerance in Zymomonas mobilis},
year = {2026},
journal = {BioDesign Research},
volume = {8},
number = {2},
keywords = {Ethanol fermentation, DNA repair, CRISPR-Cas, Zymomonas mobilis, RecN},
url = {https://www.sciopen.com/article/10.1016/j.bidere.2026.100088},
doi = {10.1016/j.bidere.2026.100088},
abstract = {Engineering polyploid industrial microorganisms is hindered by their intrinsic capacity to repair induced mutations, limiting the efficiency of genome editing and directed evolution. Using the ethanologenic bacterium Zymomonas mobilis— a polyploid alphaproteobacterium that exhibits exceptionally efficient microhomology-mediated end joining (MMEJ)— we demonstrate that RecN is essential for MMEJ and homologous recombination (HR) in vivo. Strikingly, a specialized mutant RecN-K35A, with strongly impaired ATP hydrolysis, specifically blocks MMEJ while leaving HR fully intact. The physiological importance of RecN-mediated MMEJ is highlighted by the cell elongation phenotype and increased stress sensitivity observed in the RecN-K35A mutant. Based on this connection, we developed a high-phosphorus cultivation strategy that increases cellular DNA content and significantly enhanced ethanol fermentation efficiency under industrial stress conditions. In summary, this work defines RecN as a key ATP-dependent effector of MMEJ and positions it as a potential engineering target for modulating DNA repair pathway choice and stress tolerance in Z. mobilis. Moreover, the essential role of RecN in both HR and MMEJ suggests that RecN-deficient polyploid strains could facilitate directed evolution by preventing repair of newly introduced mutations, offering a new strategy for strain improvement.}
}