Patent ID: 8003390

Claim:
A method for protecting Rhodobacter sphaeroides cells from damage in the presence of singlet oxygen, the method comprising the steps of: providing in the cells a σ E and a σ E -binding anti-sigma agent to obtain treated cells, at least one of the σ E and the anti-sigma agent being encoded by a non-native form of SEQ ID NO:2 and SEQ ID NO:1, respectively, that reduces binding between the σ E and the anti-sigma agent, the non-native form of σ E comprising a mutation selected from the group consisting of K38E, K38R, and M42A, the non-native form of the anti-sigma agent comprising a mutation selected from the group consisting of H6A, H31A, C35A, C35S, C38A, C38S, C38R and C187/189S, thereby protecting the treated cells from damage in the presence of singlet oxygen; and measuring protection of the treated cells from damage in the presence of singlet oxygen, wherein the protection is greater in the treated cells than in Rhodobacter sphaeroides cells in which binding between σ E and the anti-sigma agent is not reduced.