Gram-positive bacteria are a group of bacteria that have a thick cell wall made primarily of peptidoglycan. This structure allows them to retain a purple dye during a laboratory staining process called the Gram stain, which is used to classify bacteria. They are typically spherical (cocci) or rod-shaped (bacilli) and can be found in various environments, including soil, water, and the human body. These bacteria can be beneficial or harmful. Some Gram-positive bacteria, like Lactobacillus, are important for digestion and food production, while others, such as Staphylococcus aureus, can cause infections. Understanding their characteristics helps in developing treatments and antibiotics.