Abstract
A number of the antibiotics were tested for their effect on the multiplication of tobacco mosaic virus (TMV, ordinary strain in Japan) using the leaf-culture method previously reported by the authors.4, 9, 10)
Twenty disks, per each test, 12mm in diameter (approximately 0.6g flesh weight), were cut from a detached tobacco half-leaf (Nicotiana tabacum, Turkish) that had been inoculated with TMV one day ago. These disks were floated on the solution of an antibiotic in a petri dish and were kept in a constant-temperature chamber of 25°C under continuous illumination from fluorescent lamps. The other 20 disks cut from the opposite half-leaf were placed on distilled water and served as control. After 5 days from inoculation (4 days' incubation in test solutions), the disks were removed and rinsed with distilled water. The amount of TMV synthesized within the disks was determined by chemical methods. The data are presented in Table 1 which indicate the percentages of inhibition of TMV multiplication by some of the antiviral substances analyzed by two different methods. It is evident that the percentages of inhibition are generally lower by the TMV-protein analysis (ammonium sulphate-precipitation method9)) and are higher by the TMV-nucleic acid analysis (TCA method by Bancroft and Curtis1)). Moreover, the latter method was proved to be more accurate than the former method in estimating the different amount of TMV synthesized. Therefore, the method by Bancroft and Curtis was mostly used in the following experiments.
Of about 30 preparations tested, as shown in Table 2, the following antibiotics showed 20 per cent or more inhibition to TMV multiplication under our experimental conditions: Actidione, Naramycin, Fermicidin, Aureomycin hydrochloride, Tetracycline hydrochloride, Dextromycin sulfate, Kanamycin sulfate, and Mitomycin-C.
