Toxicity of free riboflavin and methionine–riboflavin solutions to Phytophthora infestans and the reduction of potato late blight disease

Treatments of sporangia and zoospores of Phytophthora infestans race 1.2.3.4 with methionine or riboflavin for durations of up to 8 h under fluorescent light did not affect its colonization of rye-seed agar. In contrast, exposure of sporangia and zoospores to methionine-riboflavin mixture for 2 h or more resulted in the failure of race 1.2.3.4 to grow when transferred to rye-seed agar medium. Hyphal growth of races 1.2.3.4 and 0, when incubated in liquid synthetic medium, was inhibited by free riboflavin. Potato plants, Solanum tuberosum cv. Kennebec, when pretreated with a methionine–riboflavin mixture and then spray inoculated with race 1.2.3.4 developed fewer diseased leaves per plant than plants pretreated with water, methionine, or riboflavin. Key words: Solanum tuberosum, hydroxyl radical, superoxide anion.

A standardized monitor for the control of ethylene oxide sterilization cycles

SUMMARYThe resistance of spores ofB. subtilisvar.nigerproduced in liquid synthetic medium and exposed to ethylene oxide on a nylon surface, has been shown to be almost identical to that for spores produced on a traditional solidified complex medium with exposure to the sterilant on aluminium foil. The use of short lengths of nylon tube as carriers allowed easy production and handling, with self-protection of the spore-bearing surface. Addition of a dye provided visual evidence of inoculation without affecting resistance to ethylene oxide. Such a monitor is suitable for use as a standardized biological challenge in routine ethylene oxide sterilization cycles.

THE NUTRITION OF VIBRIO COSTICOLUS: I. A SIMPLIFIED SYNTHETIC MEDIUM

A liquid synthetic medium is described in which Vibrio costicolus grows well in 24 hours. The medium contains glucose, L-cystine, L-glutamic acid, L-arginine, DL-valine, DL-isoleucine, potassium phosphate buffer, magnesium sulphate, sodium nitrate, and sodium chloride. The addition of 10 vitamins, 3 bases, 14 amino acids, and 5 salts did not improve the medium. No growth was obtained if cystine, glucose, or sodium chloride was omitted from the medium. The remaining constituents of the simplified medium were not essential but were found necessary for maximum growth. An amino acid antagonism was observed between valine and isoleucine. When added alone, either amino acid depressed the growth response, but when added together they were stimulatory.