Natural Functions of Bacterial Polyhydroxyalkanoates

Polyhydroxyalkanoates (PHAs) are energy- and intracellular carbon-storage compounds that can be mobilized and used when carbon is a limiting resource. Intracellular accumulation of PHA enhances the survival of several bacterial species under environmental stress conditions imposed in water and soil, such as UV irradiation, salinity, thermal and oxidative stress, desiccation, and osmotic shock. The ability to endure these stresses is linked to a cascade of events concomitant with PHA degradation and the expression of genes involved in protection against damaging agents. PHA synthesis involves enzymatic and transcriptional regulation, where the RpoS central stationary phase regulator sigma factor has been shown to be implicated. The energy generated during PHA degradation can also be used to drive various important energy-consuming pathways. In addition to its relevance for the plastic industry, PHA has important applications for agriculture, as those related to the production of reliable commercial inoculants, and in controlled release of insecticides when incorporated into degradable PHA granules.