Inorganic Polyphosphate in Vibrio cholerae : Genetic, Biochemical, and Physiologic Features

Abstract

ABSTRACT Vibrio cholerae O1, biotype El Tor, accumulates inorganic polyphosphate (poly P) principally as large clusters of granules. Poly P kinase (PPK), the enzyme that synthesizes poly P from ATP, is encoded by the ppk gene, which has been cloned from V. cholerae , overexpressed, and knocked out by insertion-deletion mutagenesis. The predicted amino acid sequence of PPK is 701 residues (81.6 kDa), with 64% identity to that of Escherichia coli , which it resembles biochemically. As in E. coli , ppk is part of an operon with ppx , the gene that encodes exopolyphosphatase (PPX). However, unlike in E. coli , PPX activity was not detected in cell extracts of wild-type V. cholerae . The ppk null mutant of V. cholerae has diminished adaptation to high concentrations of calcium in the medium as well as motility and abiotic surface attachment.