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Generally, the basic morphologies are spheres (coccus) and round-ended cylinders or rod shaped (bacillus). But, there are also other morphologies such as helically twisted cylinders (example Spirochetes), cylinders curved in one plane (selenomonads) and unusual morphologies (the square, flat box-shaped cells of the Archaean genus Haloquadratum ...
[31] [32] [33] Bacteria may alter their shape by simpler transitions from rod to coccoid (and vice versa) as in Escherichia coli, [34] by more complex transitions while establishing multicellularity [31] or by the development of specialized cells, structures or appendages where the population presents a pleomorphic lifestyle. [35]
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.
Many bacteria secrete extracellular polymers outside of their cell walls called glycocalyx. These polymers are usually composed of polysaccharides and sometimes protein. Capsules are relatively impermeable structures that cannot be stained with dyes such as India ink. They are structures that help protect bacteria from phagocytosis and desiccation.
Staphylococcus was one of the leading infections in hospitals and many strains of this bacterium have become antibiotic resistant. Despite strong attempts to get rid of them, staphylococcus bacteria stay present in hospitals, where they can infect people who are most at risk of infection. [4] Staphylococcus includes at least 44 species.
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.
[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.
Bacteria do not have a membrane-bound nucleus, and their genetic material is typically a single circular bacterial chromosome of DNA located in the cytoplasm in an irregularly shaped body called the nucleoid. [68] The nucleoid contains the chromosome with its associated proteins and RNA.