the biosynthesis of poly(3-hydroxybutyrate-co-3-hydroxyvalerate;P(3HB-co-3HV))in R.eutropha exemplifies the contribution of the repertoire of metabolic reactions available to an organism.R.eutropha produces P(3HB) ehen grown under appropriate condition to glucose with glucose as the sole carbon source.However,when in addition to glucose, propionic acid is added in controlled amounts, a random P(3HB-co-3HV) copolymer is formed,containing a predictable fraction of randomly distibuted 3HV units.