Many bacteria, in response to unfavourable environmental conditions, can synthesise polyesters of the polyhydroxyalkanoate (PHA) class. These biopolymers, accumulating intracellularly in the form of granules, help the bacteria to cope with negative environments and are utilised as reserve sources of carbon and energy. Rhizobacteria of the species Azospirillum brasilense synthesise a single type of PHA, poly-3-hydroxybutyrate (PHB), in response to stress factors.
