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Abstract
Temperature shock transformation (TST) uses sequential coldand hot-step treatments (0 → 42 → 0°C) to induce the uptake of exogenous DNA by chemically competent cells. This study examined the effects of the magnitude of the temperature change, as well as the cold-step temperature on transformation efficiency. Escherichia coli BW25113 transformed with the pUC19 cloning vector at cold-step temperatures of 0°C, 4°C, 10°C, and 20°C demonstrated no significant difference in transformation efficiency. When the same strain was transformed using approximately a 20°C difference between the cold-step and hot-step treatments: 0 → 20 → 0°C and 20 → 42 → 20°C, no significant difference in transformation efficiency was observed between the two treatments. Our results indicated that the cold-step temperature does not significantly affect transformation efficiency within the temperature range tested, and that the difference in temperature between the coldand hot-step treatments may be more relevant for high transformation efficiency.