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In bacteria, gene transfer occurs by three processes. These are virus-mediated transduction; [14] conjugation; [16] and natural transformation. [17] Transduction of bacterial genes by bacteriophage viruses appears to reflect occasional errors during intracellular assembly of virus particles, rather than an adaptation of the host bacteria. There ...
An S-layer (surface layer) is a cell surface protein layer found in many different bacteria and in some archaea, where it serves as the cell wall. All S-layers are made up of a two-dimensional array of proteins and have a crystalline appearance, the symmetry of which differs between species.
Some eukaryotic cells (plant cells and fungal cells) also have a cell wall. Inside the cell is the cytoplasmic region that contains the genome (DNA), ribosomes and various sorts of inclusions. [2] The genetic material is freely found in the cytoplasm. Prokaryotes can carry extrachromosomal DNA elements called plasmids, which are usually circular.
MreB is a bacterial protein believed to be homologous to eukaryal actin. MreB and actin have a weak primary structure match, but are very similar in terms of 3-D structure and filament polymerization. Almost all non-spherical bacteria rely on MreB to determine their shape.
The nucleoid (meaning nucleus-like) is an irregularly shaped region within the prokaryotic cell that contains all or most of the genetic material. [1] [2] [3] The chromosome of a typical prokaryote is circular, and its length is very large compared to the cell dimensions, so it needs to be compacted in order to fit.
Like all other organisms, bacteria contain ribosomes for the production of proteins, but the structure of the bacterial ribosome is different from that of eukaryotes and archaea. [69] Some bacteria produce intracellular nutrient storage granules, such as glycogen, [70] polyphosphate, [71] sulfur [72] or polyhydroxyalkanoates. [73]
As in other organisms, the bacterial cell wall provides structural integrity to the cell. In prokaryotes, the primary function of the cell wall is to protect the cell from internal turgor pressure caused by the much higher concentrations of proteins and other molecules inside the cell compared to its external environment.
In contrast to the magnetoreception of animals, the bacteria contain fixed magnets that force the bacteria into alignment—even dead cells are dragged into alignment, just like a compass needle. [137] Marine environments are generally characterized by low concentrations of nutrients kept in steady or intermittent motion by currents and turbulence.