Two genetic loci for resistance to kasugamycin in Escherichia coli.

There are two loci for resistance to the antibiotic kasugamycin (Ksg) in Escherichia coli. Mutations at ksgA resulted in 30S ribosomal subunit resistance to Ksg. The map location of ksgA was near minute 0.5: ksgA was 95% cotransducible with pdxA, and the apparent gene order was thr... ksgA... pdxA. Studies in stable ksgA/ksgA(+) merodiploids showed that sensitivity was dominant over resistance. Mutations at a second gene (ksgB), located between minutes 25 and 39, resulted in phenotypic Ksg(R) indistinguishable from ksgA mutations, but ribosomes from ksgB strains were sensitive to the drug in vitro. Spontaneous and induced mutations to Ksg(R) were usually of the ksgA (ribosomal) type.