Summary auto-generated
This study determined nearly complete 18S rRNA gene sequences from 28 ascomycetous yeast strains belonging to the genera Brettanomyces, Debaryomyces, Dekkera, and Kluyveromyces to elucidate their phylogenetic relationships. Sequences were amplified by PCR and analyzed using neighbor-joining and parsimony methods, with bootstrap analysis confirming significant associations. The results show that Brettanomyces anomalus and B. bruxellensis are closely related to their teleomorphs Dekkera anomala and D. bruxellensis respectively, forming a stable phylogenetic group with D. custersiana and D. naardenensis (bootstrap value 100%). Three Debaryomyces species examined were highly related (99.2-99.6% sequence similarity) and showed specific affinity with Candida guilliermondii, together forming a distinct clade. In contrast, the genus Kluyveromyces displayed marked phylogenetic heterogeneity. Seven Kluyveromyces species including K. polysporus were phylogenetically intermixed with Saccharomyces, Torulaspora, and Zygosaccharomyces species, while K. lactis, K. aestuarii, K. dobzhanskii, K. wickerhamii, and three K. marxianus varieties formed a separate monophyletic group worthy of distinct generic status. K. blattae and K. phafii each formed distinct phylogenetic lines.
Key findings
- Brettanomyces species and their teleomorphs Dekkera form a stable, monophyletic group with high bootstrap support (100%), though with minor sequence divergence (0.1-0.4%)
- Debaryomyces species are genealogically very closely related (99.2-99.6% sequence similarity) and specifically associated with Candida guilliermondii
- Kluyveromyces is not monophyletic; K. polysporus and six related species are intermixed with Saccharomyces and Zygosaccharomyces genera, while K. lactis and four other species form a distinct monophyletic group meriting separate genus status
- K. blattae and K. phafii occupy distinct phylogenetic positions not closely related to other examined ascomycetous yeasts
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Abstract
A molecular systematic investigation of members of the ascomycetous yeast genera Brettanomyces, Debaryomyces, Dekkera, and Kluyveromyces was performed by using 18S rRNA gene sequence analysis. Our comparative sequence analysis revealed that Brettanomyces anomalus and Brettanomyces bruxellensis were closely related to one another and also to their teleomorphs, Dekkera anomala and Dekkera bruxellensis, respectively. Together with Dekkera custersiana and Dekkera naardenensis, these four species formed a stable and distinct phylogenetic group. The three representative species of the genus Debaryomyces examined (viz., Debaryomyces castellii, Debaryomyces hansenii, and Debaryomyces udenii) were found to be genealogically highly related to each other and exhibited a specific phylogenetic affinity (level of sequence similarity, approximately 99.2%) with Candida guilliermondii (telemorph, Pichia guilliermondii). Debaryomyces species and C. guilliermondii formed a distinct phylogenetic group, which displayed a significant association with a phylogenetically 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 Kluyveromyces displayed very marked phylogenetic heterogeneity. Kluyveromyces polysporus, the type species of the genus Kluyveromyces, and six other Kluyveromyces species (viz., Kluyveromyces africanus, Kluyveromyces delphensis, Kluyveromyces lodderae, Kluyveromyces thermotolerans, Kluyveromyces waltii, and Kluyveromyces yarrowii) were phylogenetically intermixed with species of the genera Zygosaccharomyces, Saccharomyces, and Torulaspora. In contrast, Kluyveromyces aestuarii, Kluyveromyces dobzhanskii, Kluyveromyces lactis, Kluyveromyces wickerhamii, and three Kluyveromyces marxianus varieties, along with their anamorph, Candida kefyr, formed a highly stable monophyletic group worthy of separate generic status. Kluyveromyces blattae and Kluyveromyces phaffii formed two distinct phylogenetic lines that did not exhibit particularly close affinity with each other or other ascomycetous yeast genera. Our phylogenetic findings are discussed in the context of the results of other genotypic and phenotypic studies.