Studies on the Role of SASP in Heat and Radiation Resistance of Bacterial Sporesand on Regulation of a SASP Specific Protease

摘要

Highlights of research findings in the past three years are: (1) usingappropriate mutants lacking SASP we have shown that SASP-gamma plays no role in spore heat or UV radiation resistance, and SASP-alpha, beta and gamma play no role in spore gamma-radiation resistance; (2) we have shown that the transient high UV resistance attained during spore germination is dependent on the presence of SASP-alpha and beta; (3) using immunoelectron microscopy we have shown that alpha/beta-type SASP are associated with the forespore nucleoid, while SASP-gamma is not; (4) we have achieved high level inducible expression of an alpha/beta type SASP in E. coli. This has allowed purification of large amounts of this SASP for physical studies of its interaction with DNA. Furthermore, synthesis of this SASP gives E. coli DNA some of the properties of DNA within spores; (5) using a purified SASP we have converted the UV photochemistry of DNA in aqueous solution from thymine dimer production to spore photoproduct production; (6) physical studies of complexes formed between this purified alpha/beta-type SASP and DNA have indicated that the DNA has been converted to the A conformation upon SASP binding; (7) we have cloned, sequenced and mapped the gene (termed gpr) coding for the SASP specific spore protease. (jes)