Evolution of petite-positivity/negativity in yeasts.
Veronika Fekete (1), Silvia Poláková (1), Marika Č ierna (1), Jure Piskur (2), Pavol Sulo (1)
(1) Department of Biochemistry, Comenius University, Mlynska Dolina, Bratislava, 842 15, Slovakia; (2) Cell and Organism Biology, Lunds University, 22362 Lund, Sweden
We examined the ability to compromise the loss of mitochondrial DNA among the 95 isolates from Saccharomyces/Kluyveromyces complex and 70 isolates assigned to Brettanomyces/Dekkera genera. After the treatment with ethidium bromide (50 μg/ml) yeasts exhibit four basic phenotypes. (i) Petite-positive producing characteristic small colonies, unable to grow on nonfermentable carbon source, frequently without specific mtDNA staining patterns. Their number corresponds to the number of plated cells. (ii) Petite-negative sensitive that provide only reduced number of big grande respiring colonies. Vast number of small irregular shape minicolonies (100-1000 cells) is visible under the microscope. (iii) Petite negative resistant behave like petite-positive at low concentration of ethidium bromide but showing petite-negative phenotype at higher concentrations (200 μg/ml). (iv) Mixed petite negative and positive part of the population exhibit petite-negative, part of the population petite positive phenotype. The ability to form petites is apparently species specific and fades out with the increasing phylogenic distance from S. cerevisiae. In Dekkera/Brettanomyces group only strains assigned to Dekkera are petite-positive. B. custersianus and B. nanus are admittedly petite negative. A putative transition state are petite positive B. naardenensis where some isolates show petite negative features. This work has been supported by VEGA 1/0108/03 and Merck spol s.r.o.