Phosphatidylinositol as a Component of the Ice Nucleating Site of Pseudomonas syringae and Erwinia herbiola

Phosphatidylinositol has been identified as a major component of the ice nucleating site on the outer surface of two bacteria, Pseudomonas syringae and Erwinia herbicola . Plant lectins binding to inositol and a highly purified phosphatidylinositol-specific hydrolase (a C II lipase) inhibited or decreased the efficiency of the ice nucleating activity (INA) of both bacteria. Extracts of these two INA + bacteria had phosphatidylinositol synthase activity while extracts from related INA - Pseudomonas or Erwinia strains had no detectable synthase activity. An Escherichia coli strain acquired phosphatidylinositol synthase activity when transformed to the INA + phenotype with recombinant plasmids containing fragments of P. syringae DNA.