Citeromyces siamensis sp. nov., a novel halotolerant yeast isolated in Thailand

Y. Nagatsuka, H. Kawasaki, S. Limtong, K. Mikata and T. Seki The International Center for Biotechnology, Osaka University, 2-1 Yamada-oka, Suita-city, Osaka 565-0871, Japan Two halotolerant yeast strains, H130(T) and H149, were isolated from dry salted squid and fermented soybeans, respectively, in Thailand. Both isolates grew by multilateral budding, produced asci that had one roughened spherical ascospore and contained ubiquinone Q-8. These characteristics were shared by Citeromyces matritensis, the only species of the genus Citeromyces. Strains H130(T) and H149 were differentiated from C. matritensis by their ability to assimilate L-sorbose and L-lysine and to grow at 37 degrees C. The novel isolates were more tolerant to higher concentrations of cations (3 M NaCl or 0.8 M LiCl) and to higher osmotic pressure (60% glucose) than C. matritensis. A phylogenetic analysis of 18S rRNA gene sequence data indicated that the two novel isolates represented a sister species to C. matritensis. Furthermore, DNA--DNA hybridization data indicated that the isolates were clearly distinct from the type strain of C. matritensis (IFO 0954(T)). Based on the above characteristics, strains H130(T) and H149 are proposed to represent a novel species within the genus Citeromyces, Citeromyces siamensis; the type strain is H130(T) (=IFO 11052(T)=JCM 11522(T)=TISTR 5777(T)=CBS 9153(T)).