Texas A&M University (TAMU) BIOL112 Introductory Biology II Lab Exam 1 Practice Exam

The three basic shapes found in bacteria are coccus, bacillus, and spirillum. Each of these terms describes a distinct morphology that is fundamental to bacterial classification.

Coccus refers to spherical-shaped bacteria. These can exist as single cells, in pairs, chains, or clusters, depending on the species’ genetic and environmental factors. An example of cocci includes Streptococcus, which can form chains.

Bacillus denotes rod-shaped bacteria. This shape is typically longer and more pillar-like compared to cocci. Bacilli can also occur singly or in chains. An example is Escherichia coli, which is a commonly studied bacillus.

Spirillum describes bacteria that have a spiral or twisted shape. This morphology allows for unique movement and adaptability in various environments. An example of a spirillum is Spirillum minus, which is often found in water.

Recognizing these three shapes not only assists in identifying bacteria but is also crucial for understanding their physiological characteristics and potential ecological roles.