A study of the CaCl2 induced E. coli DH5-Alpha transformation by heat shock accompanied by vibration.

Chemical methods are commonly used for the induction of Escherichia coli (E. coli) competency to allow transformation mediated by heat shock, an essential procedure for gene cloning. Being the most labor and resource efficient chemical method, the ‘calcium chloride’ (CaCl2) method involves a brief heat shock of bacteria in the presence of Ca2+ ions. Several optimizations were made on this original protocol but the effect of vibration or rotational shaking (revolution per minute) accompanied by the heat shock has not been studied. This paper reports the effect of shaking during or after the heat shock of competent DH5-Alpha strain of E. coli, induced by CaCl2. Our results show that shaking during heat shock does not have any positive impact on the transformation efficiency. On the other hand, after the heat shock, 180 rpm shaking at 37 °C for 1 h has increased transformation efficiency significantly (P < 0.05).