Expression of the Proteus mirabilis recA gene in Bacillus subtilis is directed by its own promoter.

The recA gene of Proteus mirabilis (recApm) has been cloned into the PstI site of the Bacillus promoter-probe plasmid pPL603. When present on this plasmid, the recApm1) gene is expressed in B. subtilis under the control of its own transcriptional and translational signals. It is concluded that the high AT-content of the DNA sequence upstream of the -35 region is of decisive importance for the usage of the recApm promoter by the B. subtilis RNA polymerase. The results are discussed in relation to the expression barriers found to exist for genes from gram-negative bacteria in the gram-positive B. subtilis.