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

<i>Corynebacterium glutamicum</i> 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 <i>cgl2168</i> 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 <i>cgl2168</i> (<i>cgl2168</i> ^Δ270G) in 13032-JN significantly improved growth at 40 °C, while reverting this mutation or deleting <i>cgl2168</i> impaired thermotolerance. Structural analysis revealed the deletion extends the C-terminus with an additional α-helix. Transcriptomic profiling showed <i>cgl2168</i> ^Δ270G increased gene expressions involved in oxidative phosphorylation (e.g., <i>atpABCDEFGH</i>), nitrate metabolism (<i>narIJHK</i>), some heat shock protein genes (e.g., <i>dnaK</i> and <i>groES</i>) and deletion of <i>cgl2168</i> resulted in upregulating sulfur metabolism (sulfonate transporter protein genes <i>ssuBCD</i>, sulfur-containing amino acid <i>cys</i> and <i>met</i> operons) and central carbon metabolism (<i>gltA</i>, <i>pyc</i>), while downregulating gluconeogenesis (<i>pck</i>) and fermentation (<i>ldh</i>) 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 Cgl2168^Δ270G enhance thermotolerance by coordinating energy production, carbon metabolism, and stress adaptation, aiding industrial applications.