What does Bacillus thuringiensis (BT) specifically affect?

Bacillus thuringiensis, commonly known as BT, is a soil bacterium that is particularly effective as a biological insecticide, targeting the digestive systems of certain insects, especially caterpillars. When larvae ingest BT spores, the bacteria produce crystalline proteins that are toxic to them. These proteins are activated by the alkaline environment in the caterpillar's gut, leading to the disruption of the digestive process. This action ultimately causes the caterpillar to stop feeding and results in mortality.

Understanding the mechanism of action of BT is crucial, as it highlights its specificity; BT is designed to target specific groups of insects without causing harm to non-target species or the environment.