GENOME STRUCTURE AND REIDENTIFICATION OF THE TAXONOMIC STATUS OF PICHIA-PINUS-MH4 GENETIC LINES

Taxonomic reidentification of the methylotrophic yeast strain Pichia p inus MH4, the ancestor of the genetic lines we created [Tolstorukov et al., 1977], was carried out by comparison of genome structures and hy bridization of strain MH4 with the typical strains P. pinus NRRL y-115 82 and P. methanolica NRRL y-7685. As shown by comparative data from a pulsed-field gel electrophoresis analysis, the number and sizes of th e chromosomes of a strain designated P. pinus MH4 are identical with t hose of the typical strain P. methanolica NRRL y-7685, but differ from the typical strain P. pinus NRRL y-11582. Positive results were obtai ned in blot hybridization of the chromosomal DNA from strains NRRL y-7 685 and MH4 with the cloned genes from strain MH4. In interstrain cros ses of auxotrophic mutants, hybrids were obtained between strains MH4 and NRRL y-7685. High mating activity of these strains was observed un der conditions that were optimal for strain MH4. The hybrids obtained sporulated vigourosly and ascospores had high viability (80%). Monogen ic segregation for all parental markers of the interstrain hybrid was demonstrated by tetrad analysis. Based on the data obtained, we conclu ded that strain MH4 refers to the P. methanolica species.