Spiral bacteria, also known as spirilla, are a type of bacteria characterized by their helical or spiral shape. They belong to the group of prokaryotes, which means they lack a nucleus and other membrane-bound organelles. These bacteria can be found in various environments, including soil, water, and the intestines of animals. One well-known example of spiral bacteria is Helicobacter pylori, which is associated with stomach ulcers and other gastrointestinal issues. Spiral bacteria are motile, often using flagella to move through their surroundings. Their unique shape and movement help them navigate through viscous environments, making them effective in colonizing different habitats.