Cloning and expression of the alpha-amylase gene from Bacillus stearothermophilus in several staphylococcal species.

The plasmid-coded alpha-amylase gene of Bacillus stearothermophilus (amy) was cloned in Staphylococcus carnosus using plasmid pCA43 as a vector. The amy gene was located on a 5.4-kb HindIII DNA fragment of the hybrid plasmid pamy7. When transformed into other staphylococcal species, plasmid pamy7 exhibited marked differences in the production of alpha-amylase (alpha Amy). Most active for heterospecific alpha Amy production was Staphylococcus aureus. In its culture supernatant nearly half as much alpha Amy activity was found as for the donor strain B. stearothermophilus. All staphylococcal species were able to secrete alpha Amy, since more than 80% of the enzyme activity was found in the culture supernatant. The extracellular alpha Amy of S. aureus [pamy7] was purified to homogeneity. The enzyme exhibited an Mr of approx. 58 000, an optimum activity at pH 5.3-6.3 and at 65 degrees C. Although the enzyme was stable at 65 degrees C for at least 3 h, its thermostability was not unusual. The enzymatic properties of the alpha Amy from S. aureus were similar to those previously reported for various B. stearothermophilus strains.