Starch Agar Plates Research Articles

SUMMARY: The growth and amylase activity of a streptomycin-dependent Vibrio comma on starch agar plates was gradually decreased with decrease of the streptomycin-concentration. The concentrations of streptomycin and the streptomycin- antagonizing properties of bacterial products also could be assayed by a cup plate method. The diameters of the zones of decomposed starch around the cups were proportional to the logarithms of streptomycin concentration. In the presence of a constant concentration of streptomycin they were inversely proportional to the concentration of bacterial antagonist. The following species and genera of microorganisms produced antagonists (in decreasing order of their activity): Pseudomonas sp., Proteus morganii, Clostridium botulinum, C. parabotulinum, C. welchii, C. septi- cum, Bacillus megaterium, B. subtilis, Rhodotorula sp., and some strains of the genera Escherichia, Shigella and Klebsiella. No inhibitory effects were observed with products of Salmonella paratyphi A and B, Serratia marcescens, Staphylococcus aureus, S. albus, Streptococcus faecalis, S. lactis, Brucella abortus, B. melitensis, Pasteurella pestis, P. pseudotuberculosis, Alkaligenes faecalis, Saccharomyces sp., Candida albicans.