The SigB σ factor mediates high-temperature responses in the cyanobacterium Synechocystis sp. PCC6803

The σ factors of RNA polymerase play central roles when bacteria adapt to different environmental conditions. We studied heat-shock responses in the cyanobacterium Synechocystis sp. PCC6803 using the σ factor inactivation strains ΔsigB, ΔsigD and ΔsigBD. The SigB factor was found to be important for short-term heat-shock responses and acquired thermotolerance. The normal high-temperature induction of the hspA gene depended on the SigB factor. The SigD σ factor had a role in high-temperature responses as well, and the double inactivation strain ΔsigBD grew more slowly at 43 °C than the ΔsigB and ΔsigD strains.