2.6. Induction of mutation by ion implantation
To prepare the selected antagonistic bacterium B. licheniformis
for mutation by ion beam bombardment, the bacteria
were smeared onto a thin layer of sterile adhesive tape which
was attached to a petri dish and then placed inside a sample
holder. The holder was capable of sequentially exposing a
number of samples to the ion beam, as well as housing the
unbombarded control sample. Ion bombardment was carried
out using the mass-analyzed heavy-ion-implantation facility at
Chiang Mai University [10]. Nitrogen ions (N+) were chosen
for ion bombardment, in the energy range of 28–50 keV. Ions
were delivered at fluences of 1–10×1015 ions/cm2. Inside
the target chamber, the temperature of the target was about
0 °C. The samples were maintained under these conditions
for about 1.5–2 h, allowing for system pump-down and ion
bombardment.
After bombardment, the newly formed bacteria mutants
were cultured and any bacterial mutant that had lost the
antagonistic ability was further analyzed (as mentioned in the
dual-culture method). Genetic alterations of the bombarded