Gamma Irradiation of Bacillus subtilis Spores in the Presence of Sugars

Abstract

SUMMARYSpores of Bacillus subtilis were gamma-irradiated (soCo source) and viable counts performed by surface spread and tube dilution methods. Surface spread counts were greater than tube dilution counts by factors varying from 1-57 to 3-90 (aqueous suspensions) and 2.36 to 6.10 (freezedried). In 8 cases out of 10 there was no significant difference in the regression coefficients of log yo survivors against radiation dose for the two counting methods under identical conditions of irradiation. Freezedrying from 5 yo (w/v) aqueous solutions of glucose, lactose or fructose had a significant protective effect on the radiation resistance of the spores.Freeze-drying from aqueous suspension, or from 5 yo maltose had no effect on the resistance.

Resistance and recovery studies on ultraviolet-irradiated spores of Bacillus pumilus

“…The literature contains numerous reports on conditions which enhance the recovery of stressed or injured bacterial spores. Cook et al (6) found that after gamma radiation, surfacespread plate counts for B. subtilis were greater than those obtained by an MPN tube dilution method. On the contrary, Roberts and Aldous (20) reported that recovery of UV-irradiated organisms was better on semisolid media than on conventional agar media.…”