BIOSYNTHESIS OF POLY-3-HYDROXYBUTYRATE IN THE LUMINESCENT BACTERIUM, VIBRIO-HARVEYI, AND REGULATION BY THE LUX AUTOINDUCER, N-(3-HYDROXYBUTANOYL)HOMOSERINE LACTONE

Poly-3-hydroxybutyrate (PHB), a biopolymer of important commercial app lications, is found in a wide range of Gram-negative and Gram-positive bacteria and cyanobacteria. The present study has resulted in the ide ntification of PHB in the luminescent marine bacteria, Vibrio harveyi, in spite of it being previously classified as PHB-negative. PHB granu les with distinct membranes were detected by electron microscopy after fixation and staining of V. harveyi cells with malachite green. Analy ses by gas chromatography, nuclear magnetic resonance, infrared, and u ltraviolet spectroscopy clearly established the presence of PHB. The s ynthesis of PHB in V. harveyi was found to be under cell density regul ation with the levels increasing from 0 (<0.2) to 26 mg of PHB/g of dr y cell weight during growth in a manner analogous to the induction of luminescence in this bacteria. Moreover, synthesis of PHB in V. harvey i was shown to be controlled by the lux autoinducer, N-(3-hydroxybutan oyl)homoserine lactone, providing not only a potential link between lu minescence and PHB production but also showing that the lux autoinduce r acts as a general signal transductant. These results have also exten ded the role of homoserine lactones in metabolic regulation to include the control of synthesis of potential energy reserves.