Which bacteria helps in curdling of milk?

The bacterium that helps in the curdling of milk is Lactobacillus. Lactobacillus is a Gram-positive, rod-shaped, lactic acid bacterium (LAB) that is commonly found in milk and other dairy products. When Lactobacillus is added to milk, it converts the lactose in the milk into lactic acid, which causes the milk to curdle and form a semi-solid substance called curds. The curds can then be used to make cheese, yogurt, and other dairy products.