Physiological Studies on Drug-Resistant Bacteria 1. Physiological Study on Streptomycin-Dependent Escherichia coli

Drug-resistance of bacteria is one of the most important and also most troublesome problem in the chemotherapy of diseases. The author studied on some physiological aspects of streptomycin-dependent strain of Escherichia coli in comparison with streptomycin sensitive strain. The results are summarized as follows: 1) By inoculation of a great amount of streptomycin-sensitive E. coli on plain broth agar plates containing 1.000 γ / cc of streptomycin, one streptomycin-dependent strain was isolated. 2) The reverse mutant from this dependent strain was a streptomycin-sensitive strain, the re-reverse mutant from this reverse mutant was a dependent strain, and no resistant strain could be obtained. 3) This dependent stain could not multiply using streptomycin as the sole carbon or nitrogen source. 4) This dependent strain showed a higher requirement to streptomycin in the media containing the fatty acits related to the citric acid cycle than in those containing amino acids as its growth substrates. 5) Streptomycin showed no noticeable action on the respiration of this dependent strain. From these results, it is inferred that streptcomycin works not as a nutriment but as some working factor for the growth or multiplication of the streptomycin-dependent E. coli.