Electron Microscopy Analysis of Irradiated Bacteria

After irradiation, electron microscopy was performed to analyze cytological morphology [19 (link), 20 (link)]. All experimental bacterial strains were collected and fixed with 2.5% glutaraldehyde. The fixed cells were dehydrated by a graded series of ethanol for 15 min each step. For SEM analysis, cells were transferred to isoamyl acetate and dried in a Hitachi Model HCP-2 critical point dryer (Hitachi, Japan) with liquid CO₂. Pellets for SEM examination were coated with gold and viewed with a Hitachi SU8010SEM instrument (Hitachi, Japan). For TEM analysis, specimens were processed as described previously [20 (link)]. Ultrathin sections (70–90 nm) were stained with lead citrate and uranyl acetate and observed using a Hitachi H-7650 TEM instrument (Hitachi, Japan).