History of vitamins in fermentation — source organism for the first crystalline vitamin B12 isolation Rickes and colleagues recovered active crystalline vitamin B12 from the culture of which microorganism during early industrial vitamin research?

Introduction / Context:
Vitamin B12 (cobalamin) discovery and purification are landmark achievements linking fermentation science with nutrition and medicine. Identifying the original source organism used by Rickes and co-workers provides useful historical and scientific context for industrial vitamin production.

Given Data / Assumptions:

• The question refers to the first recovery of active crystalline B12 by Rickes et al. in the late 1940s.
• Several actinomycetes and bacteria can produce corrinoids, but not all were used in the seminal isolation.
• We are selecting the specific culture used for that classic purification.

Concept / Approach:
Streptomyces griseus, better known for producing streptomycin, was also the culture from which Rickes and colleagues at Merck first isolated crystalline vitamin B12. While later industrial processes diversified to Propionibacterium species and others, the historical attribution remains S. griseus.

Step-by-Step Solution:
Review candidate organisms historically tied to B12 research.Match Rickes et al. with Streptomyces griseus as the original source culture.Select “Streptomyces griseus.”

Verification / Alternative check:
Historical reviews of vitamin B12 discovery and Merck publications document the S. griseus source material for crystalline B12 isolation.

Why Other Options Are Wrong:
Bacillus megaterium and Propionibacterium freudenreichii are capable of corrinoid production but were not the organism of Rickes's first crystalline isolation; S. olivaceus and S. lactis lack that specific historical association.

Common Pitfalls:
Confusing later optimized production strains with the original discovery strain used for the first crystalline product.

Final Answer:
Streptomyces griseus.