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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).
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.
A small number of other unusual shapes have been described, such as star-shaped bacteria. [42] 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. [43] [44]
Gram-negative bacteria are bacteria that, unlike gram-positive bacteria, do not retain the crystal violet stain used in the Gram staining method of bacterial differentiation. [1] Their defining characteristic is that their cell envelope consists of a thin peptidoglycan cell wall sandwiched between an inner ( cytoplasmic ) membrane and an outer ...
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]
It is described using terms like brittle, creamy, sticky and dry. Staphylococci are considered to have a creamy consistency, [1]: 173 while some Neisseria species are sticky, and colonies of diphtheroid bacteria and beta-hemolytic streptococci are typically dry. [1]: 167–8 Bacteria that produce capsules often have a slimy (mucoid) consistency.
Streptococcus is a genus of gram-positive or spherical bacteria that belongs to the family Streptococcaceae, within the order Lactobacillales (lactic acid bacteria), in the phylum Bacillota. [2] Cell division in streptococci occurs along a single axis, thus when growing they tend to form pairs or chains, which may appear bent or twisted.