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The plasma membrane or bacterial cytoplasmic membrane is composed of a phospholipid bilayer and thus has all of the general functions of a cell membrane such as acting as a permeability barrier for most molecules and serving as the location for the transport of molecules into the cell.
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.
Spiral bacteria are another major bacterial cell morphology. [ 2 ] [ 30 ] [ 31 ] [ 32 ] Spiral bacteria can be sub-classified as spirilla, spirochetes, or vibrios based on the number of twists per cell, cell thickness, cell flexibility, and motility.
In bacteria, both nutrients and waste products of metabolism reach the interior of the cell by diffusion, which places an upper limit on the size of these organisms. Cells of the large sulfur bacterium Thiomargarita namibiensis, discovered in 1999, contain a large sac filled with water and nitrates, which pushes most of the cytoplasm close to ...
Thiomargarita namibiensis has a distinct genetic architecture because of its remarkable cell size and environmental niche. The DNA of T. namibiensis is dispersed over nucleoid areas situated under the cell membrane, in contrast to normal bacteria, which have a concentrated nucleoid. This peripheral design provides efficient cellular activities ...
[5] [6] The name spheroplast stems from the fact that after the microbe's cell wall is digested, membrane tension causes the cell to acquire a characteristic spherical shape. [4] Spheroplasts are osmotically fragile, and will lyse if transferred to a hypotonic solution.
A small number of other unusual shapes have been described, such as star-shaped bacteria. [44] 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. [45] [46]
M. capsulatus are thermotolerant; their cells are encapsulated and tend to have a diplococcoid shape. The cell wall is composed of three layers: outer membrane, peptidoglycan layer, and inner membrane. There are extensive intracytoplasmic membranes that are believed to be formed by invaginations of the inner cell membrane.