It has been suggested that this article be merged into Bacterial cellular morphologies. (Discuss) Proposed since December 2023.
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Spiral bacteria, bacteriaofspiral (helical) shape, form the third major morphological categoryofprokaryotes along with the rod-shaped bacilli and round cocci.[1][2] Spiral bacteria can be subclassified by the number of twists per cell, cell thickness, cell flexibility, and motility. The two types of spiral cells are spirillum and spirochete, with spirillum being rigid with external flagella, and spirochetes being flexible with internal flagella.[3]
Aspirillum (plural spirilla) is a rigid spiral bacterium that is Gram-negative and frequently has external amphitrichousorlophotrichous flagella.[3] Examples include:
Aspirochete (plural spirochetes) is a very thin, elongate, flexible, spiral bacteria that is motile via internal periplasmic flagella inside the outer membrane.[3] They comprise the phylum Spirochaetes. Owing to their morphological properties, spirochetes are difficult to Gram-stain but may be visualized using dark field microscopyorWarthin–Starry stain.[4] Examples include: