Sigma factor SigC is required for heat acclimation of the cyanobacterium Synechocystis sp. strain PCC 6803

The role of the primary-like sigma factor SigC was studied in Synechocystis. Under high temperature stress (48°C) the ΔsigC inactivation strain showed a lower survival rate than the control strain. The ΔsigC strain grew poorly at 43°C in liquid cultures under normal air. However, change to 3% CO2 enhanced growth of ΔsigC at 43°C. Differences in expression of many genes related to the carbon concentrating mechanisms between the control and the ΔsigC strain were recorded with a genome-wide DNA microarray. We suggest that
low solubility of CO2 at high temperature is one of the factors contributing to the poor thermotolerance of the ΔsigC strain.