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

The sigma 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 sigma factor inactivation strains deltasigB, deltasigD and deltasigBD. 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 sigma factor had a role in high-temperature responses as well, and the double inactivation strain deltasigBD grew more slowly at 43 degrees C than the deltasigB and deltasigD strains.