Figure 4.

Identification of members of the library of tri-alanine substitutions of σ⁷⁰ R4 carried on plasmid pVR-σ that fail to complement the temperature-sensitive rpoD800 mutation in strain PB1rpoD800 during growth at 42°C, the non-permissive temperature. (A) (Left) Demonstration of the growth-lethal effect of the rpoD800 mutation of strain PB1rpoD800 upon a shift from growth at the permissive temperature of 37°C (clear square) to 42°C (black square). (Right) Demonstration of the ability of plasmid pVR-σ carrying the wild type rpoD allele to complement the growth-lethal effect of the chromosomal rpoD800 mutation during growth at 42°C. (B)Growth curves demonstrating the failure of five members of the library of tri-alanine substitutions of σ⁷⁰ R4 to complement the growth-lethal effect of the rpoD800 mutation during growth at 42°C. Note that the growth curves of the partial diploids carrying the other 15 members of the library looked like that of PB1rpoD800[pVR-σ], i.e., full complementation (data not shown).