Question

Bacillus thuringiensis (Bt) was first isolated from a diseased silkworm by

• A. Berliner
• B. Ishiwata
• C. Dutky
• D. Knifling

Hint:

Remember the timeline:
1901: Ishiwata $\rightarrow$ Isolated from Silkworm (first isolation).
1911: Berliner $\rightarrow$ Isolated from Flour Moth and named it Bacillus thuringiensis.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Bacillus thuringiensis (Bt) is a soil-dwelling bacterium widely used as a biological pesticide and as a source of transgene inserts for insect-resistant genetically modified crops.

Step 2: Detailed Explanation:
Let us trace the history of the discovery of Bt:
The bacterium was first isolated in 1901 by the Japanese biologist Shigetane Ishiwata.
He isolated the bacterium from diseased larvae of the silkworm, Bombyx mori, which were dying from "sotto disease" (sudden-collapse disease).
He named the organism Bacillus sotto, but his description was not officially recognized internationally.
Later, in 1911, the German scientist Ernst Berliner isolated the same bacterium from the diseased larvae of the Mediterranean flour moth (Ephestia kuehniella) in the province of Thuringia, Germany.
Berliner formally described and named the bacterium Bacillus thuringiensis (named after Thuringia).
Although Berliner popularized its insecticidal potential, the very first isolation from a diseased silkworm was performed by Shigetane Ishiwata.

Step 3: Final Answer:
Bacillus thuringiensis was first isolated from a diseased silkworm by Ishiwata.