Which bacterial shape is characterized by its spiral form?

The bacterial shape characterized by its spiral form is known as spirillum. This term specifically refers to bacteria that have a helical or corkscrew shape, which distinguishes them from other types of bacteria with different morphologies.

Understanding bacterial shapes is crucial in microbiology and veterinary medicine, as it aids in the identification and classification of bacteria, which can have significant implications for diagnosis and treatment in animal health.

In contrast, rod-shaped bacteria are referred to as bacilli, while coccus shapes are spherical. The option indicating a "square" shape does not apply to bacterial classification, as bacteria are not typically described in geometric terms beyond these standard shapes. Therefore, spirillum is the most accurate answer when discussing bacteria with a spiral form.