Genus/species (aliases): Issatchenkia terricola (Pichia terricola, Saccharomyces terricolus)
Classification: Ascomycete, teleomorph
Morphology:
- Cell: Reproduces by budding; ovoidal to elongate in shape, occur singly or in pairs; simple pseudohyphae may be formed.
- Colony: Malt agar: Growth is butyrous with tannish cream oval colonies.
- Spore: Spheriodal spores with a roughened appearance due to protuberances from the cell wall.
- Zygote: Unconjugated diploid cell; isolates are typically heterothallic
- Ascus: Can be either conjugated or unconjugated. House one to four ascospores and are persistent. Two spores per ascus is most typical
- Liquid Growth: Dry, climbing pellicles formed that may be moderate to heavy depending upon the strain.
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Physiological Traits:
- Fermentation: Glucose
- Assimilation: Succinate, Citrate, Ethanol, Glycerol. No assimilation of nitrate; will use ethylamine, lysine and cadaverine as sole N source; no growth in vitamin-free medium, requires thiamin.
- Growth: 37, 40 C: variable
- Growth Sensitivities: Some strains resistant to high glucose; not resistant to cycloheximide.
Ecological Traits:
Found in soils, sea water, spoiled fruit and fruit juices.
Distinguishing Features:
Diazonium Blue test yields positive results. Unlike many other Issatchenkia species I. terricola will not grow on vitamin free medium.
Role in wine:
Often acts as a spoilage yeast in fruit juices; can be part of grape juice native flora.
Sensitivities: See 'Physiological Traits" and is heat sensitive.
References:
Chavan P., et al. Natural yeast flora of different varieties of grapes used for wine making in India. Food Microbiology 2009 Dec:26(8):801-8.