For scanning electron microscopy (SEM), the cultures
were fixed in 5% (v/v) glutaraldehyde + phosphate buffer
solution for 24 h. The samples were then transferred to
a graded ethanol series (50%, 70%, 90% and 100%)
for 30 min each and finally to amyl acetate solution (Deo
et al., 1983). Critical point dried samples were
(POLARON CPD) coated with gold-palladium using a
Polaron SC7620 Sputter Coater for 90 s. The coated
specimens were examined in a Jeol JSM-5600 LV
scanning electron microscope.