The occurrence of bacteria on the surface of plants was
observed using a scanning electron microscope (JSM-6360,
Jeol). The plant material for observation was prepared
according to a modified version of Baker’s method. Fresh
plant fragments were cut into approximately 1 cm2 pieces and fixed by immersion in 2% glutaraldehyde in 0.1 M
cacodylate buffer (pH 7.2) for at least 1 h. The samples
were drained and placed in three consecutive 1 h washes
of 0.1 M cacodylate buffer. Samples were then stored in
fresh cold cacodylate buffer for transport to the electron
microscopy laboratory. Samples were dehydrated in
a series of acetone–water washes for 15 min each and
critical-point dried with liquid CO2. Finally, samples were
sputter coated with a thin layer of gold–palladium and the
distribution of bacteria on the plants and their morphological
differentiation were observed at several magnifications
under the scanning electron microscope.