Polyhydroxyalkanoate Inclusion Body-Associated Proteins and Coding Region in Bacillus megaterium

Polyhydroxyalkanoic acids (PHA) are carbon and energy storage polymers that accumulate in inclusion bodies in many bacteria and archaea in response to environmental conditions. This work presents the results of a study of PHA inclusion body-associated proteins and an analysis of their coding region in Bacillus megaterium 11561. A 7,917-bp fragment of DNA was cloned and shown to carry a 4,104-bp cluster of 5 pha genes, phaP, -Q, -R, -B, and -C. The phaP and -Q genes were shown to be transcribed in one orientation, each from a separate promoter, while immediately upstream, phaR, -B, and -C were divergently transcribed as a tricistronic operon. Transfer of this gene cluster to Escherichia coli and to a PhaC(−) mutant of Pseudomonas putida gave a Pha(+) phenotype in both strains. Translational fusions to the green fluorescent protein localized PhaP and PhaC to the PHA inclusion bodies in living cells. The data presented are consistent with the hypothesis that the extremely hydrophilic protein PhaP is a storage protein and suggests that PHA inclusion bodies are not only a source of carbon, energy, and reducing equivalents but are also a source of amino acids.