Which type of bacteria is known for being spherical and linked with common infections?

The type of bacteria known for being spherical is called cocci. Cocci are typically round or oval in shape and can be found in various forms, such as single cells, pairs, chains, or clusters. This shape allows them to be easily identified under a microscope, and they are commonly associated with various infections including streptococcal and staphylococcal infections.

In terms of their clinical significance, cocci are a predominant form of bacteria that can cause numerous diseases in humans. Common examples of cocci include Staphylococcus aureus and Streptococcus pneumoniae, which are well-known pathogens responsible for a variety of infections.

The other types of bacteria listed are not spherical. Bacillus refers to rod-shaped bacteria, spirilli are spiral-shaped, and vibrio are comma-shaped. Each of these bacterial shapes corresponds to different properties and behaviors, leading to different types of infections and implications in both human health and disease.