A PHYLOGENETIC ANALYSIS OF SACCHAROMYCES SPECIES BY THE SEQUENCE OF 18S-28S RIBOSOMAL-RNA SPACER REGIONS

Sequences of two internally transcribed spacer regions between 18S and 28S rRNA genes were determined to assess the phylogenetic relationshi p in the strains belonging to the genus Saccharomyces. The sequences o f S. bayanus and S. pastorianus were quite similar, but not identical. Two phylogenetic trees constructed by the neighbor-joining method sho wed that all the species examined were distinguished from one another. The Saccharomyces sensu stricto species: S. cerevisiae, S. bayanus, S . paradoxus and S. pastorianus, were closely related and far from the Saccharomyces sensu late species including S. barnetti, S. castellii, S. dairensis, S. exiguus, S. servazzii, S. spencerorum and S. unisporu s, and an outlying species, S. kluyveri. (C) 1997 John Wiley & Sons, L td.