Bacterial cellular morphologies

Bacterial cellular morphologies are the shapes that are characteristic of various types of bacteria and often key to their identification.

Generally, the basic morphologies are spheres (coccus) and round-ended cylinders or rod shaped (bacillus).

Cocci can grow in pairs, chains, or clusters, depending on their orientation and attachment during cell division.

[7] Coccoid bacteria often occur in characteristic arrangements and these forms have specific names as well;[8] listed here are the basic forms as well as representative bacterial genera:[3] The gram-positive cocci are a large group of bacteria with similar morphology.

Members of some genera are identifiable by the way cells are attached to one another: in pockets, in chains, or grape-like clusters.

This genus, Neisseria, is divided into more than ten different species, but most of them are gram negative and coccoid.

The gram-negative, coccoid species include: Neisseria cinerea, N. gonorrhoeae, N. polysaccharea, N. lactamica, N. meningitidis, N. mucosa, N. oralis and N. subflava.

This genus, Moraxellaceae, comprises gram-negative coccobacilli bacteria: Moraxella lacunata, M. atlantae, M. boevrei, M. bovis, M. canis, M. caprae, M. caviae, M. cuniculi, M. equi, M. lincolnii, M. nonliquefaciens, M. osloensis, M. ovis, M. saccharolytica, and M. pluranimalium.

[14] However, only one has a morphology of diplococcus, M. catarrhalis, a salient pathogen contributing to infections in the human body.

The name Bacilli, capitalized but not italicized, can also refer to a less specific taxonomic group of bacteria that includes two orders, one of which contains the genus Bacillus.

[20] Bacilli usually divide in the same plane and are solitary, but can combine to form diplobacilli, streptobacilli, and palisades.

[23] Bacilli usually divide in the same plane and are solitary, but can combine to form diplobacilli, streptobacilli, and palisades.

[25] The word coccobacillus reflects an intermediate shape between coccus (spherical) and bacillus (elongated).

Haemophilus ducreyi, another medically important Gram-negative coccobacillus, is observed in sexually transmitted disease, chancroid, of Third World countries.

Researchers discovered a protein that allows the bacterium Vibrio cholerae to morph into a corkscrew shape that likely helps it twist into — and then escape — the protective mucus that lines the inside of the gut.

[34] A spirillum (plural spirilla) is a rigid spiral bacterium that is gram-negative and frequently has external amphitrichous or lophotrichous flagella.

Owing to their morphological properties, spirochetes are difficult to Gram-stain but may be visualized using dark field microscopy or Warthin–Starry stain.