Streptomycin sulfate is an aminoglycoside antibiotic, that inhibits protein synthesis. In Vitro: Strain RB1 shows enhanced susceptibility to streptomycin as the concentration of CV in the growth medium increases. As the CV concentration in the growth medium increases, both cytochrome aa3 levels and streptomycin susceptibility increase. Cytochrome aa3 is necessary for accumulation of streptomycin by B. subtilis^[1]. Streptomycin influences tRNA selection. Streptomycin resistance mutations generally map to protein S12 and most of these variants exhibit increased levels of discrimination in the tRNA selection process^[2].