Hyperproduction of Exocellular Levansucrase by Bacillus subtilis: Examination of the Phenotype of a sacUh Strain

The induction parameters of levansucrase synthesis were the same in Bacillus subtilis strain 168 Marburg and in a derivative, hyperproducing (sacUh) strain. However, only the hyperproducing strain showed an induction lag period. The kinetics of appearance of functional levansucrase mRNA was established. Strain 168 did not release levansucrase, but washing the cells with high ionic strength buffer released different proteins of which levansucrase represented 2%. In contrast, the great majority of levansucrase synthesized by the hyperproducer was released in a homogeneous form into the culture medium. In this case high ionic strength treatment caused the cells to release the remaining levansucrase but not other proteins. A Triton X-100 sensitive form of levansucrase was isolated by phenol treatment of the sacUh strain; this form was absent in strain 168. We suggest that the sacU gene product possibly controls the synthesis of cellular components with which levansucrase is associated and thus its release is normally prevented.