A brief description of the basic structure, special structure and function of bacteria (figure)

The structure of bacteria includes basic structures and special structures.
cell walls, cell membranes, cytoplasms and nucleosomes are the basic structures, and the diaphragms, whiplash, germs and buds are the special structures of certain bacteria. the basic structure of
bacteria is mainly composed of cell wall, cell membrane, cytoplasm, nucleias and other parts, some bacteria also have the membrane, whiplash, bacteria hair, cilia and other special structures.
the diameter of the vast majority of bacteria is between 0.5 and 5 m.
. The cell wall is a thick, tough and resilient membrane structure located at the outermost part of the cell. the thickness of the
varies from bacteria to bacteria and is generally 15-30nm. the main component of
is peptide polysaccharides, which are made up of N-acetyl glucan and N-acetyl cell wall acid, which are connected into large molecules by beta-1,4 glycoside bonds.
N-acetyl cell wall acid molecules have four peptide side chains, adjacent polysaccharides between the short peptides through the peptide bridge (Gram-positive bacteria) or peptide bonds (Gram-negative bacteria) bridge dating together, forming a peptide polysaccharides layer, like plywood, bonded into multiple layers. polysaccharides in
polysaccharides are the same in each species, while lateral short peptide chains have differences between species.
the walls of Gram-positive bacteria cells are about 20-80nm, with 15-50 layers of peptide polysaccharides, each layer 1nm thick, containing 20-40% phosphoric acid, and some have a small amount of protein.
the walls of Gram-negative bacteria are about 10nm thick, only 2-3 layers of peptide polysaccharides, and other components are more complex, with lipopolysaccharides, bacterial outer membranes and lipoproteins being from the outside.
, there is a gap between the outer membrane and the cells.
peptide polysaccharides are the main components of gram-positive bacterial cell walls, and any substance that can destroy the structure of peptide polysaccharides or inhibit its synthesis has a bactericidal or bactericidal effect.
such as lysozyme is N-acetyl cytose, penicillin inhibits the activity of transpeptide enzyme, inhibits the formation of peptide bridges.
the function of bacterial cell walls to maintain cell shape, inhibit mechanical and osmosis damage (Gram-positive bacteria can withstand 20kg/cm2 pressure), mediate cell-to-cell interactions (invasion of the host), prevent macromolecule invasion, and assist in cell movement and division.
off-walled cells are called bacterial protoplasms or spherical bodies (due to incomplete de-walling), and the ability to survive and move is greatly reduced after de-walling.
, cell membrane is a typical unit membrane structure, thickness of about 8 -10nm, the outer close to the cell wall, some Gram-negative bacteria also have an outer membrane.
usually does not form an endocosphragm system, except for ribonucleosis, there are no other eukaryotic cells, and the electron transfer chain for breathing and photosynthesis is located on the cell membrane.
some pronuclear organisms (blue bacteria and purple bacteria) for photosynthesis, the inner pleats of the membrane form a pigmented inner membrane, which is related to the light capture reaction.
some Ofthei-positive bacterial membrane pleats form a small tubular structure, called the midmembrane or interbody, the midmembrane body expands the surface area of the cell membrane, improves metabolic efficiency, has the name of the proposed mitochondria, in addition to possible dna replication.
bacterial cell membrane function: the electron transfer chain for breathing and photosynthesis is located on the cell membrane.
some photosynthesis pronuclear organisms (blue bacteria and purple bacteria), the inner pleats of the membrane form a pigmented inner membrane, which is related to the light capture reaction.
some gram-positive bacterial membrane spleies form a small tubular structure, called the midmembrane body (mesosome) or interbody, the midmembrane body expands the surface area of the cell membrane, improves metabolic efficiency, is called the proposed mitochondria (Chondroid), in addition to possible dna replication.
, cytoplasm bacteria, like other pronuclear organisms, do not have nuclear membranes, and DNA is concentrated in the low electron density region of the cytoplasm, known as nucleosomes, or nucleosomes.
bacteria generally have 1-4 nucleosomes, more than 20.
nucleosomes are ring-shaped double-stranded DNA molecules, containing a amount of genetic information can encode 2000-3000 kinds of proteins, space construction is very streamlined, there are no inclusions.
because there is no nuclear membrane, so DNA replication, RNA transcription and protein synthesis can be carried out simultaneously, unlike eukaryotic cells, these biochemical reactions are strictly separated in time and space.
each bacterial cell contains about 5000-50,000 ribosomes, some attached to the inside of the cell membrane, mostly free of cytoplasm.
bacterial ribosomes have a deposition coefficient of 70S, consisting of large subunits (50S) and small subunits (30S), which contain 23SrRNA, 5SrRNA and more than 30 proteins, and 16SrRNA and more than 20 proteins.
small subunits of 30S are sensitive to tetracycline and streptomycin, and 50S are sensitive to erythromycin and chloramphenicol.
genetic factors, called plasmids, that can be autonomously replicated in addition to the DNA of the bacterial nucleus.
plasmids are exposed ring-shaped double-stranded DNA molecules with genetic information of 2-200 genes that can replicate themselves and sometimes integrate into nuclear DNA.
plasmid DNA is very important in genetic engineering research, and is often used as a carrier of gene recombination and gene transfer.
cytoplasmic particles are particles in the cytoplasm, which temporarily store nutrients, including polysaccharides, lipids, polyphosphates, etc.
bacterial cytoplasm function: genetic factors, called plasmids, that can be autonomously replicated outside of the DNA of the bacterial nucleus.
plasmids are exposed ring-shaped double-stranded DNA molecules containing 2 to 200 genes, which can replicate themselves and sometimes integrate into nuclear DNA.
plasmid DNA is very important in genetic engineering research, and is often used as a carrier of gene recombination and gene transfer.
cytoplasmic particles are particles in the cytoplasm, which temporarily store nutrients, including polysaccharides, lipids, polyphosphates, etc.
4. The special structure of bacteria 1, the most appearance of many bacteria in the membrane is also covered with a layer of polysaccharides, the boundary is obviously called the diaphragm (capsule), such as pneumococcal bacteria;
the membrane is of great importance to the survival of bacteria, bacteria can not only use the membrane to resist adverse environment, protect themselves from white blood cells, but also have the ability to selectively adhere to the surface of specific cells, showing the ability to attack the target cells.
, for example, typhoid salmonella can specifically invade intestinal lymphatic tissue.
the filament bacteria of the bacterial membrane can also store the digestive enzymes secreted by the bacteria for attack on target cells.
2, whiplash is the moving organ of certain bacteria, consisting of a elastin called flagellin, which is structurally different from the whiplash of eyre.
bacteria can change the state of motion by adjusting the direction of whiplash rotation (both and counterclockwise).
3, the hair of bacteria is in some bacteria surface there is a more fine, shorter and straight hard silk, must be observed with electric mirror.
characteristics are: fine, short, straight, hard, multi, bacteria hair and bacterial movement is not related, according to the shape, structure and function, can be divided into common bacteria hair and sexual hair two categories.
the former is related to bacterial adsorption and infestation of the host, while the latter is a hollow tube, which is related to the transmission of genetic material.
cilia, a movement-like protrusion protruding from the surface of some eukaryotic cells.
4, spores in certain bacteria under certain conditions, cytoplasm dehydration concentration, in the bacteria to form a circular or oval, thick wall, refractive strong, very low water content, very high resistance of the dormant body, called spores or spores.
because each cell only forms a spore, so the formation of spores is asexual reproduction, spores on nutrition, energy needs are very low, strong resistance, can protect bacteria through the bad environment, with less water content, thick and dense film, shell no permeability, the core contains a variety of heat-resistant enzymes and so on, so the heat, drying, chemical disinfectant and other physical factors are extremely strong resistance. the formation of
spores is an extremely complex process, including morphological structure, chemical composition and other changes.
mainly goes through the following stages in structure: (1) nuclear material fusion into axial filament (rod-shaped).
(2) at the center or end of the cell, the cell membrane traps to form a diaphragm surrounding the nuclear material, creating a small cell.
(3) small cells are surrounded by the original cell membrane, producing pre-spores.
pre-spores are essentially a protoplasm surrounded by two layers of concentric membranes.
look at unstained live bacteria under an optical microscope, the presporations can be seen as a clear area that is significantly different from the rest of the bacteria.
(4) before spores are then surrounded by multi-layer membranes, such as the cortex, spores, etc., and eventually become mature spores, released due to the collapse of the cell wall. The special structure of
bacteria mainly includes whiplash, germ, diaphragm and bud cells.
whiplash is a bacterial motor organ consisting of simple keratin-myoproteins.
bacteria hair is divided into common bacteria hair and sex hair two kinds, ordinary bacteria hair can be linked to the host cell surface of the plum receptor, play a disjointed role, and the sex hair hollow is tube-like, can be transmitted between bacteria through the bonding of genetic material, so the genetic variation of the bacteria of the bacteria related to medicine - academic education network collection and finishing.
the membrane is a layer of polysaccharide outside the cell wall with antigen, which can resist the body's phagocytosis.
bud spys is a breeding body of certain bacteria, under certain environmental conditions, due to the concentration of cytosal dehydration concentrated into a circular or egg round small body, with multi-layer membrane structure, strong resistance to external chemical factors, can be hidden for several years or decades after re-breeding growth.
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