Spirochetes use an axial filament to be motile. This is similar to a cellular flagella but this structure wraps through the whole cell. It is located between the periplasmic space between the inner and outer membranes of the cell.

Axial Filament 

Which of the following best describes spirochete cells?

Which of the following statements is true about spirochete cells?

Which of the following diseases is commonly associated with spirochete bacteria?

What is a distinguishing feature of spirochete bacteria?

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

University of Michigan - Ann Arbor

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Tulane University

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

Cell Morphologies

The gram negative bacteria that are not present in the Proteobacteria phylum consist of some of these classes and genera of bacteria:
-  *Chlamidia*
- Spirochetes
- *Cytophaga, Fusobacterium, and Bacteroides*
- Planctomycetes

Non-proteobacteria Gram Negative Bacteria

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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

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?

Planctomycetes are a phylum of bacteria that are typically water dwelling. Unlike many bacteria, they reproduce via budding rather than binary fission. A bud separates from the mother cell. Sessile cells are immobile and contain a holdfast appendage that allows them to adhere to surfaces in the water. The sessile cells are able to reproduce.

Planctomycetes

Gram negative bacteria have a thin layer of peptidoglycan. They also have an inner and outer membrane. The outer membrane contains the lipopolysaccharides which are important in gram negative bacteria being infectious. 

Gram Negative Cell Walls

The *Chlamydia* genus consists of many pathogens. They spread very easily from host to host because they form elementary bodies during their life cycle. These are spore-like which allows *Chlamydia* to be metabolically inactive until they are in a host environment.

*Chlamydia*

This phylum contains gram-negative nonproteobacteria that are linked together because of their similarities in their DNA sequences. They are rod bacteria that are primarily living in anaerobic environments and many of which are fermenters.

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