PHOSPHATE CONCENTRATION REGULATES TRANSCRIPTION OF THE ACINETOBACTER POLYHYDROXYALKANOIC ACID BIOSYNTHETIC GENES

The polyhydroxyalkanoic acid (PHA) biosynthetic gene locus was cloned and characterized from an Acinetobacter sp. isolated from activated sl udge. Nucleotide sequence analysis identified three clustered genes, p haA(Ac) (encoding a beta-ketothiolase),phaB(Ac) (encoding an acetoacet yl coenzyme A reductase), and phaC(Ac) (encoding a PHA synthase). In a ddition, an open reading frame (ORF1) with potential to encode a 13-kD a protein was identified within this locus. The sequence of the putati ve translational product of ORF1 does not show significant similarity to any sequences in the database. A plasmid containing the Acinetobact er pha locus conferred the ability to accumulate poly-beta-hydroxybuty rate on its Escherichia coli host. These genes appear to lie in an ope ron transcribed by two promoters upstream of phaB(Ac), an apparent con stitutive promoter, and a second promoter induced by phosphate starvat ion and under pho regulon control. These as well as a number of additi onal potential transcription start points were identified by a combina tion of primer extension and promoter-chloramphenicol acetyltransferas e gene fusion studies carried out in Acinetobacter or E. coli transfor mants.