Electron microscopy studies were carried out as previously reported with some modifications. The cells of E. carotovora subsp. carotovora were fixed by glutaraldehyde–OSO4 fixation. Logarithmic phase cells of E. carotovora subsp. carotovora (each approximately 109 CFU/L) were treated with neomycin at 0.004 g/L for different periods of time. The cells were then collected by centrifugation and washed with 0.05 mol/L sodium phosphate buffer (PBS), pH 7.0. The samples were transferred to fresh 0.5% glutaraldehyde, and kept for 30 min at 4 C, centrifuged at 13,000 r/min, and fixed in 3% glutaraldehyde. The cells were further fixed in 1% OSO4, dehydrated in graded solutions of acetone, and embedded in
Epon812. Ultrathin sections were cut and stained with uranyl acetate and lead citrate. All sections were examined under a RILI H-600IV electron microscope.