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[2] [3] [4] Coccus refers to the shape of the bacteria and can contain multiple genera, such as staphylococci or streptococci. Cocci can grow in pairs, chains, or clusters, depending on their orientation and attachment during cell division. In contrast to many bacilli-shaped bacteria, most cocci bacteria do not have flagella and are non-motile. [5]
Cell shape is generally characteristic of a given bacterial species, but can vary depending on growth conditions. Some bacteria have complex life cycles involving the production of stalks and appendages (e.g. Caulobacter) and some produce elaborate structures bearing reproductive spores (e.g. Myxococcus, Streptomyces).
A small number of other unusual shapes have been described, such as star-shaped bacteria. [47] This wide variety of shapes is determined by the bacterial cell wall and cytoskeleton and is important because it can influence the ability of bacteria to acquire nutrients, attach to surfaces, swim through liquids and escape predators. [48] [49]
Cyanobacterial morphology refers to the form or shape of cyanobacteria. Cyanobacteria are a large and diverse phylum of bacteria defined by their unique combination of pigments and their ability to perform oxygenic photosynthesis. [2] [3] Cyanobacteria often live in colonial aggregates that can take a multitude of forms. [3]
Bacterial morphological plasticity refers to changes in the shape and size that bacterial cells undergo when they encounter stressful environments. Although bacteria have evolved complex molecular strategies to maintain their shape, many are able to alter their shape as a survival strategy in response to protist predators, antibiotics, the immune response, and other threats.
[1]: 167–8 Bacteria that produce capsules often have a slimy (mucoid) consistency. [2]: 495 When certain microorganisms are grown on blood agar, they may digest the blood in the medium, causing visible hemolysis (destruction of red blood cells) on the agar plate. In colonial morphology, hemolysis is classified into three types: alpha-, beta ...
However, this is not true pleomorphism, as individual virions are not changing shape, but being succeeded by virions with different shapes. One example is the bacterial viruses of the Plasmaviridae family. [13] A group of haloarchaeal viruses has been shown to exhibit pleomorphism as well. [14]
The bacterial flagellum is made up of protein subunits of flagellin. [12] Its shape is a 20-nanometer-thick hollow tube. It is helical and has a sharp bend just outside the outer membrane; this "hook" allows the axis of the helix to point directly away from the cell.