Mitochondria - Tool for taxonomic identification of yeasts from Saccharomyces sensu stricto complex

Mitochondrial genomes of Saccharomyces and close relatives previously used for transplacement of mitochondria to S, cerevisiae were examined. The orig ins of replication in mitochondrial DNA, the presence of nuclear and mitoch ondrial polymorphic loci and the ability to produce mitochondrial respirati on-deficient mutants were used to reclassify some collection yeasts and to assign others into four separate subgroups. The first included isolates ide ntical to Saccharomyces cerevisiae (S. italicus. S. oviformis, S. chevalier i and S. capensis) which possess 5 or more replication origins. The second group consists of S, paradoxus (var. douglasii) mitochondrial genome with t he equal number of ori sequences but incompatible mitochondria. The third g roup represents Saccharomyces sensu stricto petite-positive species (S, car lsbergensis, S. heterogenous, S. uvarum, S. willianus) with 1-2 origins of replication significantly different from S. cerevisiae. In addition, the lo cus between tRNA(fMet) and tRNA(PRO) is about one-half of the 1400 bp membe rs of S. cerevisiae complex. The last group includes isolates that do not b elong to Saccharomyces sensu stricto group as they are petite-negative and devoid of any S. cerevisiae-like replication origins.