Field emission scanning electron microscopy of GAS biofilms. 24-h biofilms of the M1- and M41-type GAS strains were grown on glass cover slips and analyzed by FESEM. (a-b) Architecture of GAS microcolonies shown at low magnification. (c-d) Cell surface morphology and cell-to-cell junctions observed at higher magnification. Enlargements of cell-to-cell junctions are shown below.