Bacillus thuringiensis

Bacillus thuringiensis (Bt) is a Gram-positive, soil-dwelling bacterium, commonly used as a biological pesticide. It is a parasporal crystal containing endotoxin, which is released in the gastrointestinal tract of insects and causes death.

History

Bt was first discovered in 1901 by Japanese biologist Shigetane Ishiwatari. As the bacterium was originally isolated from the silkworm, it was named Bacillus thuringiensis to signify this origin.

Characteristics

Bt is characterized by its ability to form a parasporal crystal protein during the stationary phase of its growth cycle. The crystal proteins, known as delta endotoxins, are insecticidal and are encoded by cry genes.

Use in Pest Control

Bt strains have been developed for control of insect pests such as Lepidoptera, Coleoptera, Diptera and Orthoptera. Each strain produces different delta endotoxins, making the bacterium capable of targeting specific pests. The specificity of these toxins is determined by the presence of specific binding sites in the gut of the insect.

Safety

Bt products are considered safe for humans and the environment. They have been approved for use by the Environmental Protection Agency (EPA) and are exempt from food residue tolerance requirements.

Resistance Management

Resistance to Bt products by insect pests is a growing concern. Strategies for managing resistance include high-dose/refuge strategies, pyramid strategies, and the use of Bt in combination with other control methods.

See Also

• Biological pesticide
• Gram-positive bacteria
• Soil-dwelling bacteria
• Endotoxin
• Gastrointestinal tract
• Insecticide
• Environmental Protection Agency (EPA)

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