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Abstract
SUMMARY: Bacillus cereus strain 569H became resistant to tetracyclines, arsenite and cyanide. The degree of resistance acquired was independent of the inducing concentration up to 2 × 10−5 m. Recovery from tetracycline and arsenite inhibition involved a change in the bacteria themselves; cyanide resistance involved also the destruction of this inhibitory agent. Although there were many similarities between the tetracycline and arsenite recoveries, two distinct mechanisms were involved. Adaptation to tetracycline was not observed with B. megaterium, Pseudomonas aeruginosa or Escherichia coli. Bacillus megaterium and E. coli did adapt to cyanide. Although polymyxin B was inactive by itself against B. cereus, lytic activity due to the antibiotic was seen when a tetracycline was also present in the medium. The lytic activity ceased when the bacilli recovered from tetracycline. Bacillus cereus did not adapt to other inhibitors of protein synthesis, RNA synthesis or oxidative phosphorylation.
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