Question

Who first reported the symbiotic association between yoghurt starter cultures Streptococcus thermophilus and Lactobacillus delbruecki ssp. bulgaricus

• A. Joseph Lister
• B. Robert Koch
• C. Orla Jensen
• D. Fanny Hesse

Hint:

Remember that Sigurd Orla-Jensen is considered the father of modern lactic acid bacteria taxonomy. His 1919 monograph established the biochemical classification of dairy starter cultures.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Yoghurt manufacture relies on the symbiotic, proto-cooperative relationship between two species of lactic acid bacteria: Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus.
This relationship allows both organisms to grow faster and produce acid more efficiently than they would individually.
Detailed Explanation:
The mutual stimulation (symbiosis) between S. thermophilus and L. delbrueckii subsp. bulgaricus is characterized by reciprocal nutrient exchange:
- Initially, S. thermophilus grows rapidly, producing carbon dioxide, formic acid, and purines.
- These substances stimulate the growth of the more fastidious L. delbrueckii subsp. bulgaricus.
- In return, L. delbrueckii subsp. bulgaricus exhibits high proteolytic activity, breaking down milk proteins into peptides and amino acids (especially valine), which are required by S. thermophilus.
- This mutualistic, symbiotic association was first detailed and published by the Danish dairy bacteriologist Sigurd Orla-Jensen in his seminal 1919 monograph "The Lactic Acid Bacteria".
- Evaluating the other options:
- Joseph Lister: isolated the first pure bacterial culture (Bacterium lactis) in 1873.
- Robert Koch: formulated Koch's postulates and introduced solid media techniques.
- Fanny Hesse: suggested using agar-agar as a solidifying agent for bacterial media.
Therefore, Orla-Jensen is credited with first reporting this symbiotic relationship.
Final Answer:
Orla Jensen first reported the symbiotic association between yoghurt starter cultures. Hence, the correct option is (C).