Regulation of gene expression under high hydrostatic pressure: the versatile role of the master regulator SurR in energy metabolism

In <i>Thermococcales</i>, energy metabolism genes are regulated by the sulfur-responsive transcriptional regulator SurR. In the piezophilic archaeon <i>Thermococcus barophilus</i>, these genes are also influenced by hydrostatic pressure. To explore the interaction between pressure, sulfur availability, and gene regulation, we constructed and analyzed several deletion mutants, including a partial <i>surR</i> knockout, under varying conditions. Our results show that hydrostatic pressure modulates the expression of energy metabolism genes and that SurR is essential for activating the hydrogenogenic gene cluster, even in sulfur-rich environments. Under sulfur limitation, the membrane-bound sulfur-reducing complex (MBS) is required for normal growth. These regulatory patterns expand current models derived from non-piezophilic species such as <i>Pyrococcus furiosus</i> and <i>Thermococcus kodakarensis</i>. Overall, our findings indicate that hydrostatic pressure shapes SurR function in <i>T. barophilus</i>, reflecting its adaptive plasticity in extreme environments.