PGA has diverse physiological functions that vary according to
the species synthesizing it and its environment. Soil bacteria
(mostly from the genus Bacillus, but excluding B. anthracis) use
the released PGA for sequestration of toxic metal ions, thereby
increasing their resistance to adverse environments. PGA may also
be a source of glutamate for bacteria during starvation in the late
stationary phase (Kimura et al., 2004). Two highly pathogenic bacteria
viz., B. anthracis and Staphylococcus epidermidis synthesizes
surface-associated PGA, which enables them to escape phagocytosis,
and enables them to act as virulence factor. Furthermore, B.
anthracis capsule is composed exclusively of the D-enantiomer,
making it particularly non-immunogenic. This capsule also prevents
antibodies from gaining access to the bacterium. It protects
B. anthracis against phage infections and S. epidermidis against antimicrobial
peptides, probably by acting as a passive barrier. Thus,
anchored PGA is a bacterial virulence factor that protects the pathogen
from the immune system, whereas released PGA may be a
persistence factor that protects the bacterium from its environment.
Natrialba asiatica use PGA to decrease high local salt concentrations,
enabling them to survive in a hostile environment