TABLE 1.

Frequencies of transformation with competent cells and electroporation and of conjugation in E. coli DH5α recombinant clones and V. vulnificus strains

Recipienta	Mean transformation frequency (log10 no. of transformants/μg of DNA) ± SD (n = 3)b		Mean conjugation frequency (log10 no. of transconjugants/ no. of recipients)  ± SD (n = 3)c
	With competent cells	By electroporation
E. coli
DH5α(pUC19)	5.7 ± 0.1	4.7 ± 0.1	−0.2 ± 0.1
DH5α(pSI014)	0.0 ± 0.0d	2.2 ± 1.9d	−0.1 ± 0.1
V. vulnificus
YJ016	3.2 ± 0.3	ND	−3.5 ± 0.1
SK005	4.3 ± 0.1d	ND	−3.8 ± 0.5

^apSI014 was a pUC19 derivative containing the intact vvn gene, YJ016 was a clinical isolate, and SK005 was an isogenic mutant deficient in Vvn (ND mutant). 

^bCompetent cells were prepared by treatment with divalent ions. The bacteria (1 × 10⁹ to 3 × 10⁹ CFU), washed or competent cells, were transformed with 5 ng of pJRD215 DNA in both methods. Transformation frequencies were calculated according to the number of transformants obtained under this condition. ND, not determined. 

^cThe recipients were mated with E. coli S17-1(pJRD215) for 3 h at recipient/donor ratios of 1:10 and 10:1 for E. coli and V. vulnificus, respectively. 

^dSignificant difference (P < 0.01) between the two strains by two-tailed Student t test.