PHYLOGENETIC-RELATIONSHIPS AMONG MEMBERS OF THE ASCOMYCETOUS YEAST GENERA BRETTANOMYCES, DEBARYOMYCES, DEKKEM, AND KLUYVEROMYCES DEDUCED BYSMALL-SUBUNIT RIBOSOMAL-RNA GENE-SEQUENCES

A molecular systematic investigation of members of the ascomycetous ye ast genera Brettanomyces, Debaryomyces, Dekkera, and Kluyveromyces was performed by using 18S rRNA gene sequence analysis, Our comparative s equence analysis revealed that Brettanomyces anomalus and Brettanomyce s bruxellensis were closely related to one another and also to their t eleomorphs, Dekkera anomala and Dekkera bruxellensis, respectively, To gether with Dekkera custersiana and Dekkera naardenensis, these four s pecies formed a stable and distinct phylogenetic group, The three repr esentative species of the genus Debaryomyces examined (viz., Debaryomy ces castellii, Debaryomyces hansenii, and Debaryomyces udenii) were fo und to be genealogically highly related to each other and exhibited a specific phylogenetic affinity (level of sequence similarity, approxim ately 99.2%) with Candida guilliermondii (teleomorph, Pichia guillierm ondii). Debaryomyces species and C. guilliermondii formed a distinct p hylogenetic group, which displayed a significant association with a ph ylogenetically coherent cluster encompassing Lodderomyces elongisporus , Candida albicans, and four other Candida species, In contrast to the situation with the genera Brettanomyces and Debaryomyces, the genus K huyveromyces displayed very marked phylogenetic heterogeneity, Kluyver omyces polysporus, the type species of the genus Kluyveromyces, and si x other Kluyveromyces species (viz., Kluyveromyces africanus, Kluyvero myces delphensis, Kluyveromyces lodderae, Kluyveromyces thermotolerans , Kluyveromyces and Kluyveromyces yarrowii) were phylogenetically inte rmixed with species of the genera Zygosaccharomyces, Saccharomyces, an d Torulaspora. In contrast, Kluyveromyces aestuarii, Kuyveromyces dobz hanskii, Kluyveromyces lactis, Kluyveromyces wickerhamii, and three Kl uyveromyces marxianus varieties, along with their anamorph, Candida ke fyr, formed a highly stable monophyletic group worthy of separate gene ric status, Kluyveromyces blattae and Khyveromyces phaffii formed two distinct phylogenetic lines that did not exhibit particularly close af finity with each other or other ascomycetous yeast genera, Our phyloge netic findings are discussed in the context of the results of other ge notypic and phenotypic studies.