TABLE 1 .

Spontaneous competence occurs on human pharyngeal cells

Strainsa	Substrate	Recombination frequencyb
S2Tet + S4Str	Pharyngeal cells	4.3 × 10−4 ± 2.1 × 10−4
S2Tet + S4Str	Immobilized cells	1.2 × 10−4 ± 7.0 × 10−5
S2Tet + S4Str	Abiotic	3.3 × 10−7 ± 4.1 × 10−7
S2Tet + S4Str	Pharyngeal cells without serum	6.2 × 10−4 ± 3.8 × 10−4
S2Tet + S19FTmp	Pharyngeal cells	1.5 × 10−4 ± 9.2 × 10−6

^aStr, streptomycin; Tet, tetracycline; Tmp, trimethoprim.

^bMean ± standard deviation from three independent experiments.