Inducible Resistance to d -Cycloserine in Bacillus subtilis 168

Abstract

Resistance to d -cycloserine could be induced in Bacillus subtilis 168 by sublethal concentrations of d -cycloserine. Sensitivity to the antibiotic could be regained by growth in the absence of d -cycloserine. The bactericidal activity of d -cycloserine apparently was not altered by resistant cells, and peptidoglycan synthesis was still inhibited by d -cycloserine in resistant cells. The d -cycloserine resistance apparently resulted from a decreased uptake of the antibiotic. The decrease in d -cycloserine transport could be prevented by simultaneous treatment of the cells with rifampin and d -cycloserine. d -Cycloserine was transported by the same system as glycine in B. subtilis . d -Cycloserine was able to exchange for intracellular glycine in both sensitive and resistant cells, suggesting that d -cycloserine is not excluded from the cell in resistant cultures.