What is formed by Bacillus thuringiensis during a particular phase of their growth ?

Carbohydrate molecules. Lipid crystals . Protein crystals. All of these.

Protein crystals.

Bt Cotton: Some strains of Bacillus thuringiensis produce proteins that kill certain insects such as lepidopterans (tobacco budworm, armyworm), coleopterans (beetles) and dipterans (flies, mosquitoes). B. thuringiensis forms protein crystals during a particular phase of their growth.