Transcription of ppk from Acinetobacter sp. Strain ADP1, Encoding a Putative Polyphosphate Kinase, Is Induced by Phosphate Starvation

Polyphosphate kinase (Ppk) catalyzes the formation of polyphosphate from ATP. We cloned theppk gene (2,073 bp) fromAcinetobacter sp. strain ADP1; this gene encodes a putative polypeptide of 78.6 kDa with extensive homology to polyphosphate kinase fromEscherichia coli and other bacteria. Chromosomal disruption ofppk by inserting a transcriptionally fusedlacZ does not affect growth under conditions of phosphate limitation or excess. β-Galactosidase activity expressed from the single-copyppk ::lacZ fusion is induced 5- to 15-fold by phosphate starvation. An increased amount ofppk transcript (2.2 kb) was detected when cells were grown at a limiting phosphate concentration. Primer extension analysis revealed a regulated promoter located upstream of a second, constitutive promoter. Potential similarities of this regulation with the effects of PhoB and PhoR ofE. coli are discussed.