ELECTRON-MICROSCOPIC EXAMINATION OF THE EXTRACELLULAR POLYMERIC SUBSTANCES IN ANAEROBIC GRANULAR BIOFILMS

Scanning electron microscopy revealed that collapsed extracellular pol ymeric substances (EPS) surrounded bacteria present in granular sludge . Treatment of granular sludge with whole-cell antiserum and staining with polycationic ferritin demonstrated that bacteria were enveloped b y extensive EPS. Antibody stabilization permitted a visualization of t he EPS which more closely resembled its natural hydrated state. The EP S was seen to completely fill the intercellular spaces in the microcol onies. Both pure and mixed microcolonies were observed to be enclosed by EPS. The presence of these large amounts of EPS indicates that this extracellular layer is important in maintaining the structural integr ity of granular sludge.