Fig. 3 Effect of Mg2+ on the inhibitory

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2 Fig. 1 Effect of TC,CP on growth and pyocyanine production. (I) Incubation at for 96 hrs. œ- œ TC (average of 6 strains) - CP (average of 3 strains) Solide line: growth, Broken line: pyocyanine. Fig. 3 Effect of Mg2+ on the inhibitory ocyanine. function of TC against pigment production. (I) 0.1% MgSO4.7H20 was added at the same time of inoculation, in the broth containing TC 12.5 mcg/ml,then incubated for 96hrs. Test strain: Ps. aerug. 31, Solide line: growth, Broken line: pyocyanine. Fig. 2 Effct of TC on growth and pyocyanine production. (II) (Time-course) Incubation at Average of 6 strains. œ- œ TC 25.0mcg/m1 - TC 0.4mcg /ml, Solide line: growth, Broken 'line : py-

3 Fig. 4 Effect of Mg2+ on the inhibitory function of TC against pigment production. (II) 0.1% MgSO4.7H20 was added in the broth containing TC 12.5mcg/ml at various time after inoculation, then incubated for 96hrs. Test strain: Ps. aerug. 31, Solide line: growth, Broken line: pyocyanine. Table 1. Effect of removal of TC Test strain: Ps. aerug. 31

4 Fig. 5 Effect of time of incorporation of antibiotics during. The course of bacterial growth. Incubation at for 72hrs., after the addition of antibiotcs. œ- œ TO 6.3mcg/ml, - CP 12.5 mcg/ml, Test strain : Ps. aerug. 31, :Sonde line : growth, Broken line : pyocyanine. Fig. 7 Effect of EM on growth and pyocyanine production. Incubation at 37 Ž for 96hrs. Average of 2 strains. Solide line: growth, Broken line: pyocyanine Fig. 6 Effect of GM on growth and pyocyanine production. Incubation at 37 Ž for 96hrs. Average of 3 strains. Solide line : growth, Broken line : pyocyanine.

5 Fig. 8 Effect of CER on growth and pyocyanine production. Incubation at 37 Ž for 96 hrs. Average of 3 :strains. Solide line : growth, Broken line: pyocyanine. Fig. 10 Effect of CL, PL-B on growth and pyocyanine production. Incubation at 37 Ž for 96hrs. Average of 3 strains, œ- œ CL, - PL-B, Solide line: growth, Broken line: pyocyanine. Fig. 9 Effect of SM growth and pyocyanine production. Incubation at 37 Ž for 96hrs. œ- œ average of 2 strains. - Ps. aerug. 32 Solide line: growth, Broken line: pyocyanine.

6 Fig. 11 Effect of PC-G on growth and pyocyanine production. Incubation at for 96hrs. Average of 7 strains. Solide line: growth, Broken line: pyocyanine. Table 2. Effect of removal of PC-G Average of 3 strains

7 Fig. 12 Effect of AB-PC on growth and pyocyanine production. Incubation at 37 Ž for 96hrs. Average of 5 strains. Solide line: growth, Broken line: pyocyanine.

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9 1) Wahba, A. H.: The Identification of Atypical Strains of Pseudomonas aeruginosa, J. gen. Microbiol., 38: , ) Fujita, H.: Influence of Antibiotics on The Production of Pyocyanin and Fluorescin by Pseudomonas aeruginosa and The Occurrenc of Non-pyocyanin Strains from Clinical Specimens, Mie Medical J., , : , ) Halpern, Y. S., Teneh, M. and Grossowicz. 4) Schneierson, S. S., Amsterdam, D. and Perlman, E.: Inhibition of Psendomonas aeruon of Pyocyanine by Nonproliferating N.: Further Evidence for The Producti- Su- ginosa Pigment Formation by Chloramphenicol and Erythromycin, Antibi. and Chemothera., 10: 30-33, ) Grossowicz, N., Hayat, P. and Halpern, Y. S.: Pyocyanine Biosynthesis by Pseudomonas aeruginosa, J. gen. Microbiol., , ) Frank, L. H. and DeMoss, R. D.: On The Biosynthesis of Pyocyanine, J. Bacteriol., spensions of Pseudomonas aeruginosa, J. Bacteriol., 83: , The Influence of Antibiotics on the Pyocyanine-production by Pseudomonas aeruginosa Ichita YOSHIZAWA Department of Microbiology, Showa Pharmaceutical (Director: Assist. Prof. Taketoshi Arai) College Recently the rate of the isolation of non-pigment producing strains of Ps. aeruginosa tended to increase according to the observations of various workers. Therefore, investigations were made to observe the influence of addition of various antibiotics to the media on the pyocyanine production of Ps. aeruginosa. Tetracycline, chloramphenicol, erythromycin and gentamicin inhibited apparently the pyocyanine production even at the concentration at which no growth inhibition was noted. In the case of tetracycline the mechanism of suppression of pigment production was thought to be due to the decrease of metallic ions in the media by chelating. Although the high concentration of cephaloridine did not cause the inhibition of growth, it showed distinct inhibition of pigment production at considerably high concentration. The influence of streptomycin varied according to the sensitivity of the used strain. Streptomycin-sensitive strains showed considerable decrease of pigment production by the addition of low level of the drug. Colistin and polymyxin B showed no influence on the pyocyanine production. The pyocyanine production was apparently enhanced by high concentration of benzylpenicillin or ampicillin, pyocyanine being produced about twice as high in the broth containing 10,000 units of benzylpenicillin as the control culture. The added antibiotics did not seem to induce the mutation of pyocyanine-producing activity of the used strain of Ps.aeruginosa, because the washed cells from the broth culture containing antibiotics showed quite the same pigment production as the original culture.