Putative membrane protein Cgl2168 and its variant enhance thermotolerance in Corynebacterium glutamicum.

Corynebacterium glutamicum ATCC 13032 is widely used as the chassis strain for industrial production of various amino acids, but its thermotolerance limits productivity under high temperatures. Comparative genomic analysis in this study identified cgl2168 as a key determinant of enhanced thermotolerance in a laboratory strain (13032-JN) compared to another stock (13032-TJ). A guanine at Residue 270 (G270) deletion in cgl2168 (cgl2168 Δ270G) in 13032-JN significantly improved growth at 40 °C, while reverting this mutation or deleting cgl2168 impaired thermotolerance. Structural analysis revealed the deletion extends the C-terminus with an additional α-helix. Transcriptomic profiling showed cgl2168 Δ270G increased gene expressions involved in oxidative phosphorylation (e.g., atpABCDEFGH), nitrate metabolism (narIJHK), some heat shock protein genes (e.g., dnaK and groES) and deletion of cgl2168 resulted in upregulating sulfur metabolism (sulfonate transporter protein genes ssuBCD, sulfur-containing amino acid cys and met operons) and central carbon metabolism (gltA, pyc), while downregulating gluconeogenesis (pck) and fermentation (ldh) genes. These changes enhanced ATP synthesis, carbon utilization and oxidative tolerance. Predicted interactors of Cgl2168 linked it to respiratory chain function, stress responses, and cell envelope biogenesis. Thus, Cgl2168 and its variant Cgl2168Δ270G enhance thermotolerance by coordinating energy production, carbon metabolism, and stress adaptation, aiding industrial applications.