Analysis of a hybrid between Kluyveromyces marxianus and Kluyveromyces thermotolerans by physiological profile comparison, isoenzyme electrophoresis, DNA reassociation, and restriction mapping of ribosomal DNA

Abstract

A hybrid yeast strain (LAC/MAL), obtained by Johannsen and van der Walt (1978. Arch. Microbiol. 118:45–48) by growing together strains of Kluyveromyces marxianus (LAC/mal) and Kluyveromyces thermotolerans (lac/MAL), was studied. The nutritional profiles of the hybrid and of some segregants derived from the hybrid indicated that they were more similar to K. marxianus than to K. thermotolerans. This was confirmed by the electrophoretic analysis of isoenzymes, by DNA/DNA reassociation studies, and by restriction endonuclease mapping of ribosomal DNA cistrons. These analyses further indicated that the parent strain identified as K. thermotolerans was atypical of that species. The accumulated evidence ruled out the possibility that the hybrid strain was the result of Mendelian recombination but suggested that some form of transformation might have taken place.