These bacterial cells lack a cell wall, thus they do not have a stable shape. They may appear as round bodies or interlacing filaments. 

Mycoplasmas

Coccus bacteria are round and spherical in shape.

Coccus

Bacterial cells that are rod shaped are bacilli. Bacilli are capable of forming endospores. 

Bacillus

These bacterial cells are curved rod shaped. 

Vibrio

Coccobacilli bacteria are short rod shaped bacteria. 

Coccobacillus

Spirilla are rigidly spiraled shaped bacterial cells.

Spirillum

Spirochete cells are longer and helical spiral bacterial cells. They are members of the Spirochaetota phylum of bacteria.

Spirochete

Pathogenic bacteria are bacteria that can cause infectious disease.

Pathogenic Bacteria

Which of the following bacterial morphologies is characterized by a spiral shape?

Which bacterial morphology is described as rod-shaped?

Which bacterial morphology is described as spherical in shape?

Which bacterial morphology is described as comma-shaped?

Bacteria can be classified based on their different morphologies.
- Coccus
- Bacillus
- Vibrio
- Coccobacillus
- Spirillum
- Spirochete

University of Michigan - Ann Arbor

University of Wisconsin - Madison

Tulane University

Bacteria are classified based on size, shape and arrangement. 

Morphology & Classification of Bacteria

https://openstax.org/details/books/microbiology/

Microbiology covers the scope and sequence requirements for a single-semester microbiology course for non-majors. The book presents the core concepts of microbiology with a focus on applications for careers in allied health. The pedagogical features of the text make the material interesting and accessible while maintaining the career-application focus and scientific rigor inherent in the subject matter. Microbiology’s art program enhances students’ understanding of concepts through clear and effective illustrations, diagrams, and photographs.

Microbiology is produced through a collaborative publishing agreement between OpenStax and the American Society for Microbiology Press. The book aligns with the curriculum guidelines of the American Society for Microbiology.

OpenStax Microbiology Textbook

Studying the morphology of bacteria requires using microscopes. The types of microscopes are:
- Optical microscope
- Phase contrast microscope
- Dark ground microscope
- Electron microscope

Microscopy

Due to the lack of contrast in light microscopes, observation of structural details in live bacteria is not possible. Staining specimens adds contrast to the image. This involves dying and fixing the specimen, subsequently killing the bacteria. Commonly used staining techniques are:
- Simple Stains
- Negative Staining
- Impregnation Methods
- Differential Stains

Stained Preparations

Cell Morphologies

- Arrangements of Cocci
- Arrangements of Bacilli

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