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

Abstract

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.