TABLE 2.

Nucleotide sequence analysis of the rpoB alleles from independent Rif^r dnaN⁺ and dnaN159 isolates

Nucleotide positionb	rpoB mutations identified in straina:
	JL100 (dnaN+)		JL103 (dnaN159)
	Base substitution	No. of occurrences	Base substitution	No. of occurrences
1455	ND	NA	TA→ CG	1
1534	ND	NA	TA→ CG	1
1546	GC→ AT	4	GC→ AT	10
1576	GC→ AT	5	CG→ AT	4
1586	GC→ AT	1	GC→ AT	4
1592	GC→ AT	1	GC→ AT	3
1691	GC→ AT	4	ND	NA

^aCultures of the indicated strains were spread on LB plates supplemented with Rif (100 μg/ml) and incubated overnight at 30°C. A single Rif^r isolate from each plate was colony purified prior to PCR amplification of the rpoB gene, as described previously (12). The nucleotide change(s) in rpoB alleles leading to Rif^r in independent Rif^r isolates of strains JL100 (dnaN⁺; 15 isolates) and JL103 (dnaN159; 22 isolates) were determined by automated nucleotide sequence analysis (Biopolymer Facility, Roswell Park Cancer Institute, Buffalo, NY), as described previously (38). Each Rif^r dnaN⁺ isolate examined contained a single rpoB mutation, while one of the Rif^r dnaN159 isolates contained two mutations (TA→ CG at position 1455 and GC→ AT at position 1586). Abbreviations: ND, none detected; NA, not applicable.

^bThe position of each mutation identified is indicated, with position 1 referring to the A in the ATG initiation codon of rpoB.