Genetic transformation of Bacillus brevis 47, a protein-secreting bacterium, by plasmid DNA

A method has been developed for introducing plasmid DNA into Bacillus brevis 47, a protein-secreting bacterium. Treatment of B. brevis 47 cells with 50 mM Tris-hydrochloride buffer of alkaline pH was effective for inducing DNA uptake competence. In the presence of polyethylene glycol, the Tris-treated cells incorporated plasmid DNA with a frequency of 10(-4) (transformants per viable cell) when 1 microgram of plasmid DNA was added to 10(9) Tris-treated cells. The pH of Tris-hydrochloride buffer as well as the concentration and molecular weight of the polyethylene glycol affected the transformation frequency. The growth phase of B. brevis 47 cells strongly influenced the frequency. Two plasmids, pHW1 and pUB110, have been introduced into B. brevis 47 by this method. The mechanism of induction of competence for DNA uptake in connection with removal of the outer two protein layers of the cell wall by treatment of B. brevis 47 cells with Tris-hydrochloride buffer is discussed.