TABLE 2.

Frequencies of S-R dissociation and of detection of the GI-2 deletion

Strain	Growth conditions	Dissociation frequency (10−2)a	Frequency of detection of GI-2 deletion by:
			PCR (10−3)b	qPCR (10−5)c
B. melitensis 16M	37°C, pH 6.6, 10 days	0.1 ± 0.03	Not detected	10 ± 3
B. suis 1330	37°C, pH 6.6, 10 days	0.7 ± 0.10	Not detected	67 ± 15
B. abortus 2308	37°C, pH 6.6, 10 days	2.7 ± 0.25	4.5 ± 1.1	900 ± 210
B. melitensis 16M	37°C, late-stationary phase	Not detected	Not detected	1.0 ± 0.21
B. suis 1330	37°C, late-stationary phase	Not detected	Not detected	1.3 ± 0.25
B. abortus 2308	37°C, late-stationary phase	Not detected	Not detected	2.9 ± 0.32

^aR colonies were identified by using the crystal violet dye exclusion test, and the dissociation frequency was calculated with respect to the total colony count.

^bPCR detection of the chromosomal scar was carried out for each R colony, and then the GI-2 deletion frequency was assessed (values represent the means and standard errors of the means of results from three independent experiments).

^cValues represent the means and standard errors of the means of results from three independent experiments. The frequency of detection of the GI-2 deletion was estimated as the ratio between the numbers of scars and genome copies. The efficiency (E) of the PCR obtained within the range of 10⁶ to 10² target copies was 1.84 ± 0.07.