Interspecific Discontinuity in the Genus Clavispora Rodrigues de Miranda by Phenetic Analysis, Genomic Deoxyribonucleic Acid Reassociation, and Restriction Mapping of Ribosomal Deoxyribonucleic Acid

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Abstract
Heterothallic strains belonging to the biologically distinct yeast species Clavispora opuntiae and Clavispora lusitaniae were studied by three different methods. The type cultures of the two yeast species exhibited 8% relatedness as measured by reassociation of unique deoxyribonucleic acid. Ten strains of C. opuntiae and nine strains of C. lusitaniae were compared on the basis of their physiological phenotypes and the restriction maps of their ribosomal deoxyribonucleic acid (rDNAs). Although the two species possessed many similarities as well as certain amounts of intraspecific variation by both approaches, they appeared to constitute well-defined entities. Unlike C. opuntiae, C. lusitaniae always utilized L-rhamnose as the sole carbon source and was resistant to 10 mg of cycloheximide per liter. Strains of C. opuntiae did not utilize L-lysine as the sole nitrogen source or utilized it very weakly, whereas all strains of C. lusitaniae grew rapidly on this compound. By contrast, the hydrolysis of Tween 80 and the utilization of lactic acid, citric acid, and hexadecane tended to be more pronounced in C. opuntiae. The rDNA repeating unit was 9.0 kilobases long in C. lusitaniae, as compared with 7.6 kilobases in C. opuntiae. The conserved region identified previously in the rDNA of C. opuntiae was found almost intact in the rDNA of C. lusitaniae, but the variable regions differed substantially between the two species.