TABLE 3.

Frequency of streptomycin-resistant mutants of M. smegmatis strains carrying different numbers of functional rrn and rpsL genes

Strain	No. of rrn operons	No. of rpsL genes	Median mutation frequencya	Mutation frequency range
M. smegmatis mc2 155 (wild type)	2	1	1.3 × 10−8	6.6 × 10−8–1.5 × 10−9
M. smegmatis rpsL3+	2	3	<2 × 10−12
M. smegmatis rrnB	1	1	6.6 × 10−9	2.1 × 10−8–1.3 × 10−9
M. smegmatis rrnB rpsL3+	1	3	4.4 × 10−10	1.3 × 10−8–2.0 × 10−10

^aMedian from at least five experiments.