microbiology, Vol 140, 1613-1617, Copyright © 1994 by Society for General Microbiology
A rapid and simple method for Bacillus subtilis transformation on solid media
PM Hauser and D Karamata
Institut de Genetique et Biologie Microbiennes, Lausanne, Switzerland.
Cells of Bacillus subtilis strains 168 and W23 deprived of an amino acid or
a base on a given solid medium were found to develop competence. We
describe a rapid and simple method of genetic transformation of this
organism consisting in spreading a sample containing 1 microgram DNA and
10(7) exponentially growing cells of an auxotrophic mutant onto plates
devoid of the required amino acid or base. After overnight incubation,
about 100-200 prototrophic transformants per plate were obtained, i.e. a
frequency of about 10(- 5), as compared to 10(-4) routinely obtained by the
method of transformation in liquid medium with frozen competent cells.
Plasmids and other chromosomal or plasmid-borne markers, which cannot be
directly selected for, were transferred by congression. The dependence of
the transformation efficiency on cell density, medium richness, incubation
time and the nature of transforming DNA was investigated. We conclude that
the development of competence accompanies amino acid or base starvation of
cells under appropriate physiological conditions.
