Spirilla are a type of bacteria characterized by their spiral or corkscrew shape. They belong to the group of prokaryotes, which means they lack a nucleus and other membrane-bound organelles. Spirilla can be found in various environments, including soil and water, and some species are known to be motile, using flagella to move. These bacteria are often classified under the broader category of spiral bacteria, which also includes spirochetes. While some spirilla are harmless and play a role in nutrient cycling, others can be pathogenic, causing diseases in humans and animals. Understanding spirilla is important for both ecology and medicine.