Bacterium

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.

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

Scientists use a Gram stain to classify them. Gram-positive bacteria have a thick peptidoglycan layer that retains purple dye, while Gram-negative bacteria have a thinner layer and an outer membrane, appearing pink. The human body is home to trillions of

Bacteria are microscopic, single-celled organisms that exist in virtually every environment on Earth, from deep-sea vents to the human digestive tract. They are , meaning they lack a nucleus and membrane-bound organelles. While often associated with disease, the vast majority of bacteria are either harmless or essential to life. 1. Structure and Classification These are typically treated with antibiotics , though

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

Common forms include cocci (spherical), bacilli (rod-shaped), and spirilla (spiral).