Regulation of lipA gene expression by cell surface proteins in Arthrobacter photogonimos

Expression of the light-inducible lipA gene in Arthrobacter photogonimos by photodynamic compounds and visible light was inhibited by washing cells wi th 1 M KCl. Addition of cell surface extract to KCl-washed cells restored t he induction. Washing cells with 1 M MgCl2 removed a 14-kDa polypeptide and concomitantly caused expression of lipA gene without photodynamic treatmen t. The purified 14-kDa polypeptide inhibited photodynamic induction of lipA gene. These results indicated that regulation of lipA gene expression occu rred at the cell surface and involved positive and negative factors, probab ly through a signal transduction system.