Use of WL Medium to Profile Native Flora Fermentations

Vineyard, winery, barrel, and controlled temperature fermentation samples from a single commercial winery (Luna Vineyards) conducting fermentations with indigenous organisms were plated onto Wallerstein Laboratory Nutrient Agar (WL) to evaluate colony diversity. Seventeen unique colony morphologies were identified. Sequence analysis of the DNA encoding a portion of the large ribosomal 26S rRNA indicated that the colony types defined members of six genera: Hanseniaspora uvarum (Kloeckera apiculata), Saccharomyces cerevisiae, Issatchenkia orientalis, Pichia kluyveri, Candida olephelia, and Metschnikowia. Distinct colony subtypes were identified within the pulcherrimin producers traditionally classified as a single species, Metschnikowia pulcherrima. Sequence analysis of the D1/D2 region of the 26S rDNA of these biotypes showed a high degree of divergence, suggesting that these organisms might define separate species. Analysis of fermentations revealed that colony type as indicated on this medium could be used to monitor the yeast population dynamics.