Which type of bacteria is usually characterized by a rod shape?

Bacilli are the type of bacteria that are typically characterized by a rod shape. This morphological feature is significant because it helps in the classification of bacteria and can impact their behavior, metabolism, and how they are targeted by treatments.

In microbiology, bacilli refers specifically to rod-shaped bacteria, and they can vary in length and thickness. This distinguishing shape is crucial for identifying different bacterial species under a microscope, as it aids in categorizing bacteria into broader groups. Bacilli can also exhibit various arrangements, such as forming chains or clusters, which may provide additional insight into their biological characteristics and potential pathogenicity.

Other bacterial shapes, such as cocci, spirilla, and vibrio, define different structural forms. Cocci are spherical, spirilla are spiral-shaped, and vibrio are comma-shaped. While these shapes are important for distinguishing various types of bacteria, bacilli is the term that specifically relates to the rod shape noted in the question.