Eleven strains of a new species of the genus Kluyveromyces, characterized as having evanescent asci and Q-6 as the major ubiquinone, were isolated from sediments, a clam and a crab collected at depths of 1000–2000 m in Suruga Bay and Sagami Bay, Japan. A phylogenetic tree based on small-subunit (18S) rRNA gene sequences placed these isolates into a cluster of Kluyveromyces. DNA complementarity and phylogenetic trees of internal transcribed spacer (ITS) regions and 5·8S rRNA genes showed that the isolates are closely related to Kluyveromyces aestuarii, but that these two species are genetically distinct. The isolates are described as Kluyveromyces nonfermentans sp. nov. Because this species lacks the fermentative ability considered to be an important criterion for the genus Kluyveromyces, the definition of the genus has been emended. The type strain of K. nonfermentans is strain SY-33T (= JCM 10232T).
Seven strains of three new yeast species were isolated from soil, flowers and leaves in the Nansei Islands, Japan. These isolates most closely resembled Kluyveromyces phaffii in physiological characteristics and nuclear DNA base composition (30–32 mol% G+C), but on the basis of DNA-DNA hybridization and electrophoretic karyotyping they were categorized into three new species different from K. phaffii. Phylogenetic analysis using 18S rRNA gene sequence showed that the three new species and K. phaffii were highly related to one another and phylogenetically separate from the members of other species. On the basis of phylogeny and physiological characters, it is proposed that the three new species represent novel taxa and should be designated Tetrapisispora iriomotensis gen. nov., sp. nov. (type strain IFO 10929T), Tetrapisispora nanseiensis gen. nov., sp. nov. (type strain IFO 10899T) and Tetrapisispora arboricola gen. nov., sp. nov. (type strain IFO 10925T), while Kluyveromyces phaffii becomes Tetrapisispora phaffii comb. nov.