Ca2+ -dependence and inhibition of transformation by trifluoperazine and chlorpromazine in Thermoactinomyces vulgaris. 
Ca(2+) enhanced the transformation frequency of Thermoactinomyces vulgaris (stock no.  1278) of an auxotrophic strain by the chromosomal DNA isolated from a prototrophic strain (stock no.  1227).  The number of transformants showed a marked increase with increasing concentration of CaCl(2) upto 0.05 mM; and above this concentration, the transformation frequency decreased significantly.  Antipsychotic drugs that are potent calmodulin inhibitors, like trifluoperazine and chlorpromazine, when applied in the concentration range of 0.01-0.04 mM along with optimal CaCl(2) concentration to the cultures of the recipient cells, resulted in a significant inhibition in the frequency of Ca(2+)-stimulated transformation.  The results of present investigation suggest the involvement of a Ca(2+)-dependent protein activator in the development of Ca(2+)-mediated competence, which could have played an important role in the enhancement of genetic transformation in this aerobic spore forming thermophilic actinomycete.