Intraspecific variability and exopolysaccharide production in Aureobasidium pullulans.

Forty seven strains of the black yeasts, Aureobasidium pullulans and Hormonema dematioides, and the type strain of Hormonema macrosporum were examined using PCR-ribotyping and universally primed PCR with subsequent hybridization. Four groups (populations) were distinguished within A. pullulans with PCR-ribotyping, which largely coincided with UP-PCR/hybridization groups. The UP-PCR technique revealed a greater degree of heterogeneity between the groups studied. Five strains identified as Hormonena dematioides on the basis of physiological and morphological data formed a group recognizable with PCR-ribotyping and UP-PCR/hybridization, which also included H. macrosporum. Aureobasidium pullulans is characterized by the absence of RsaI restriction sites in rDNA amplified with primers 5.8S-R and LR7, while Hormonema species possessed several bands after RsaI digestion. For analysis of distance between populations, PCR-ribotyping with AluI and MspI is sufficient. Strains of A. pullulans produce exopolysaccharides in liquid media with different nitrogen sources, while the strains of Hormonema synthesize minor amounts of polysaccharides in media with peptone. Populations of A. pullulans differ slightly from each other in their optimal, medium-dependent production of polysaccharides.