A degU-containing SP beta prophage complements superactivator mutations affecting the Bacillus subtilis degSU operon.

The Bacillus subtilis degSU two-gene operon encodes a two-component regulatory system which positively controls expression of a variety of genes encoding degradative enzymes. Point superactivator mutations in either degS or degU increase the production of these enzymes. A specialized transducing SP beta phage which partially complements several of these mutations was isolated from a phage library of the B. subtilis chromosome. This phage was shown to contain the degU (wild-type) gene. This unexpected co-dominance is discussed.