SIGNIFICANCE OF DNA BASE COMPOSITION IN THE CLASSIFICATION OF YEAST GENERA CRYPTOCOCCUS AND RHODOTORULA

Abstract

DNA base composition (GC content) of 20 strains of Cryptococcus and 38 strains of Rhodotorula was investigated. Cryptococci employed exhibited the GC content of 49.0-59.5%, and were divided into 2 groups on the basis of their GC content as shown by Storck et al. The first group showed GC content of 58.8-59.5%, and comprised 5 strains representing 3 species. The second group exhibited GC content of 49.0-54.9%, and comprised 15 strains belonging to 10 taxa. The members of Rhodotorula showed the GC content of 50.0-68.5%, and were divided into 4 groups. The first group showed GC content of 66.8-68.5%, and consisted of 7 strains belonging to R. infirmominiata and R. glutinis. The second group showed GC content of 60.0-61.2%, and comprised 18 strains belonging to R. glutinis, R. glutinis var. dairenensis, R. glutinis var. rufusa, R. rubra, and R. pilimanae. The third group showed the GC content of 55.4-58.8%, and comprised 3 strains belonging to R. crocea, R. glutinis var. aurantiaca, and R. lactosa. The last group showed the GC content of 50.0-51.0%, and comprised 9 strains belonging to R. lactosa, R. pallida, R. minuta, R. marina, R. slooffii, R. zsoltii, and R. texensis. This grouping based on GC content agreed fairly well with that of Hasegawa based on requirement of specific vitamin, iodine reaction of culture broth, assimilability of lactose, optimum temperature for growth, and antigenic structure. Large intraspecific variations of GC content found in C. luteolus, C. laurentii, R. glutinis, and R. lactosa suggested the inadequateness of criteria presently employed in the classification of Rhodotorula and Cryptococcus.