CTAB-mediated, single-step preparation of competent Escherichia coli, Bifidobacteriumsp. and Kluyveromyces lactis cells

An efficient and reproducible method for transformation depends on
the competency of the organism. We have developed a simple method
for the preparation of competent Escherichia coli, Kluyveromyces lactis,
and Bifidobacterium sp. by using a buffer containing cetyl trimethyl
ammonium bromide (CTAB) and permits efficient uptake of plasmid
DNA and ligation-reaction products. Cells are harvested, washed,
mixed with 1–10 μg/ml CTAB, incubated, and followed by a buffer
wash. For long-term storage of competent cells, bacteria may be frozen
in 10% glycerolwithout the addition of other components. The transformation
process is very simple; plasmid DNA and the cells are mixed and
incubated for 5–60 min at 4 °C; no heat pulse is required, and the duration
of incubation at 4 °C is not crucial.