Biochemical Basis of Resistance to Hygromycin B in Streptomyces hygroscopicus - the Producing Organism

Abstract
Hygromycin B, an aminocyclitol antibiotic that strongly inhibits both 70S and 80S ribosomes, is synthesized by S. hygroscopicus. Ribosomes from this gram-negative mycelial bacterium are inhibited in vitro by the antibiotic. The streptomycete is highly resistant to the drug in vivo since it possesses hygromycin B phosphotransferase activity. This enzyme was shown by gel filtration to have a MW of 42,000. It modifies its antibiotic substrate to produce 7''''-O-phosphoryl-hygromycin B, which totally lacks biological activity in vivo and in vitro.