| Abstract: | We have developed a genetic transformation system for a freeze-tolerant yeast Kluyveromyces thermotolerans. K. thermotolerans spheroplasts could be transformed with a YRp-type vector containing an autonomously replicating sequence (ARS) of Saccharomyces cerevisiae. However, transformation with a YEp-type vector containing a replication origin of S. cerevisiae 2 μM DNA was not successful. The cycloheximide resistance gene (RIM-C) of Candida maltosa and the URA3 gene of S. cerevisiae were successfully used to transform a prototrophic strain of K. thermotolerans and an Ura? mutant of this yeast isolated in this study, respectively. Transformation was also possible by using intact cells treated with lithium salts or thiol compounds. The YRp-type vectors were maintained as plasmids in the transformants under selective conditions. This is the first report of successful transformation of K. thermotolerans. |
