Genetic improvement of bacterial ability to accumulate phosphate (Pi)
was investigated using Escherichia coli as a test organism. High level
s of Pi accumulation were achieved by (i) modifying the genetic regula
tion and increasing the dosage of the E. coli genes encoding polyphosp
hate kinase (ppk), acetate kinase (ackA), and the phosphate inducible
transport system (pstS, pstC, pstA, and pstB) and (ii) genetically ina
ctivating ppx encoding exopolyphosphatase. Acetate kinase was employed
as an ATP regeneration system for polyphosphate synthesis. The best r
ecombinant strain, which contained both pBC29 (ppk) and pEP02.2 (pst g
enes) accumulated approximately 10-fold more Pi than did the control s
train. The phosphorus content of this recombinant reached a maximum of
16 % on the dry weight basis (49 % as phosphate). About 65 % of the c
ellular phosphorus was stored as polyphosphate.