They break down organic matter, recycling carbon and nutrients back into the ecosystem.

The human body is home to trillions of bacteria, known as the . These "good" bacteria aid in digestion and protect against harmful pathogens. However, pathogenic bacteria cause diseases such as strep throat, tuberculosis, and urinary tract infections. These are typically treated with antibiotics , though the overuse of these drugs has led to the rise of "superbugs"—bacteria that are resistant to standard medical treatments.

Many use flagella for movement or pili to adhere to surfaces or exchange genetic material. 2. Reproduction and Growth

Engineered bacteria produce insulin, vaccines, and enzymes used in detergents. 4. Human Health and the Microbiome

In the food industry, bacteria are used to produce yogurt, cheese, pickles, and sauerkraut.

Certain bacteria in soil convert atmospheric nitrogen into a form plants can use to grow.

Bacteria are generally categorized by their shape and the composition of their cell walls: