Submitted to: Taxon
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/1/2001
Publication Date: N/A
Interpretive Summary: Gene sequence comparisons have shown that many groups of microorganisms are misclassified. Correction of this problem, which impacts on predicting the biotechnological properties of a species, often requires a proposal to an international commission. The present manuscript proposes to correct a taxonomic problem that would prevent use of the name Kluyveromyces for a group of yeasts that has industrial and genetic uses. If the proposal is not accepted, there will be considerable confusion on what is the proper name for this important group of yeasts.
Technical Abstract: Molecular analyses have demonstrated that many yeast genera, including Kluyveromyces, are not phylogenetically circumscribed. Independent studies employing phylogenetic analyses of 18S rDNA, partial sequences of 26S rDNA, ITS rDNA, cytochrome oxidase II, isozyme mobilities and restriction analysis of mitochondrial DNA have all demonstrated that Kluyveromyces is polyphyletic and that species in the K. marxianus clade (K. aestuarii, K. dobzhanskii, K. lactis, K. marxianus, K. nonfermentans, K. wickerhamii) are only distantly related to the other clades of the Saccharomycetaceae, several of which also include species assigned to Kluyveromyces. According to the molecular findings just discussed, species of the K. marxianus clade require reclassification in a genus different from that of K. polysporus. Options are accepting Zygofabospora or creating an entirely new genus, if not for the confusion that either of these two proposals would cause. Kluyveromyces marxianus and K. lactis are known and used worldwide for the fermentation of dairy wastes and for commercial production of foodgrade lactases. Additionally, a widely used genetics database has been developed for K. lactis. Were it not for K. lactis and K. marxianus, Kluyveromyces would be considered an obscure genus. This point is made clear by examining literature citations from Chemical Abstracts and Biological Abstracts. The following are averages for the citations in the two databases for the period 1990-2000: K. marxianus (and synonym K. fragilis) 649, K. lactis 736, K. polysporus 13. Fabospora and Zygofabospora averaged one citation each.