Expression of recA in Deinococcus radiodurans

Area of Science:

• Microbiology
• Molecular Biology
• Radiation Biology

Background:

• Deinococcus radiodurans exhibits extreme resistance to DNA-damaging agents.
• Its RecA protein is crucial for DNA repair but its expression is tightly regulated.
• Previous studies indicated lethal effects of D. radiodurans recA in E. coli.

Purpose of the Study:

• To investigate the function and regulation of Deinococcus radiodurans RecA protein.
• To determine if Shigella flexneri RecA can complement D. radiodurans recA phenotypes.
• To explore interspecies RecA protein functionality and regulation.

Main Methods:

• Cloning and expression of Shigella flexneri recA in recA-defective D. radiodurans.
• Assessing complementation of D. radiodurans recA phenotypes (DNA damage sensitivity, transformation, plasmid replication).
• Rescuing the cloned S. flexneri recA gene and testing its function in E. coli.

Main Results:

• Deinococcus radiodurans RecA protein is undetectable except during DNA damage, with synthesis ceasing upon growth onset.
• Shigella flexneri RecA, despite accumulation, failed to complement any D. radiodurans recA deficiency.
• The cloned S. flexneri recA gene retained functionality when tested in E. coli.

Conclusions:

• Deinococcus radiodurans and Shigella flexneri RecA proteins are not functionally interchangeable.
• Differences in induction/suppression kinetics suggest distinct modes of action for these RecA proteins.
• RecA protein functionality is species-specific, even between closely related bacteria.