Issatchenkia terricola

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.

 

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.