Bacteria: Morphological classifications

Morphological classifications of <span class="lexicon-modal"><a href="https://www.frequenz-therapie.com/en/lexikon/bacteria-and-frequency-therapy/" title="Bacteria" data-ajax-modal="modal" data-original-title=" Bacteria are microscopically small, single-celled organisms that belong to the prokaryotes. They do not have a real cell nucleus and their DNA is freely present in the cytoplasm. " data-url="https://www.frequenz-therapie.com/en/cbax/lexicon/modalInfo/d3d40cfb051f4514bd117ce9b4c80eb9">bacteria</a></span>

Morphological classifications of bacteria

Why is morphology important?

The morphology, or external shape of bacteria, is a fundamental characteristic to identify and classify them. Different shapes help bacteria to adapt to specific environments and fulfil different functions.

Main types of bacterial forms

Cocci (spherical bacteria)
These bacteria are spherical and can occur singly, in pairs (diplococci), in chains (streptococci) or in clusters (staphylococci).

Examples: Streptococcus pneumoniae (pneumonia), Staphylococcus aureus (skin infections).
Bacilli (rod-shaped bacteria)
Rod-shaped bacteria can be short or long and occasionally form endospores.

Examples: Escherichia coli (intestinal flora), Bacillus anthracis (anthrax).
Spirillae (helical bacteria)
These bacteria have a spiral or corkscrew shape and are often motile.

Examples: Spirillum volutans (aquatic bacterium).
Spirochetes (helical, flexible body)
They are similar to spirillae, but have a more flexible cell structure and move by means of endoflagella.

Examples: Treponema pallidum (syphilis), Borrelia burgdorferi (Lyme disease).
Vibrions (comma bacteria)
These bacteria have a curved, comma-like shape.

Examples: Vibrio cholerae (cholera).

Other morphological variations

Some bacteria show more complex or unusual shapes, such as:

Filamentous bacteria: Elongated cell structures