E. coli, commonly known as E. coli, was discovered by Escherich in 1885 and has been considered a part of the normal gut flora for a long period of time and is considered to be non-pathogenic. bacteria. It was not until the middle of the 20th century that it was recognized that some special serotypes of E. coli are pathogenic to humans and animals, especially to infants and young animals (avian), which often cause severe diarrhea and sepsis. It is a common prokaryote, according to Different biological characteristics classify pathogenic E. coli into six categories: enteropathogenic Escherichia coli (EPEC), enterotoxic Escherichia coli (ETEC), enteroinvasive E. coli (EIEC), enterohemorrhagic Escherichia coli ( EHEC), enteroadhesive E. coli (EAEC) and diffuse adhesion E. coli (DAEC). Escherichia coli belongs to Gram-negative bacteria (G-). Common species Escherichia coli O157:H7 serotype belongs to enterohemorrhagic Escherichia coli. It has been reported in many countries including China since 1982, and has been reported in many countries. In recent years, Japan has caused a number of large outbreaks caused by food contamination of the bacteria, which is particularly eye-catching. Among the intestinal pathogens usually isolated in the United States and Canada, it is currently ranked second or third. Escherichia coli O 157:H7 causes intestinal hemorrhagic diarrhea, about 2% to 7% of patients will develop into hemolytic uremic syndrome, the latter is most likely to occur in children and the elderly. Pathogenic E. coli causes epidemic outbreaks by polluting drinking water, food, and recreational water bodies. If the condition is serious, it can be life-threatening. Escherichia coli (E. coli) Gram-negative Brevibacterium, size 0.5 x 1-3 microns. Whole body flagellum, able to exercise, no spores. It can ferment a variety of sugars to produce acid and produce gas. It is a normal dwelling bacteria in the intestines of humans and animals. After the baby is born, it will enter the intestine with breastfeeding, and accompanying people for life, its metabolic activities can inhibit microorganisms that break down proteins in the intestine. Growth, reducing the harmful effects of protein breakdown products on the human body, but also the synthesis of vitamin B and K, as well as the bactericidal action of colicin. Under normal habitat conditions, it does not cause illness. However, if you enter the gallbladder, bladder, etc., it can cause inflammation. It is multiplied in the intestines and accounts for 1/3 of the dry weight of the feces. Facultative anaerobic bacteria. In the case of poor sanitation, the feces are often scattered in the surrounding environment. If the bacteria is detected in water and food, it can be considered as an indicator of contamination by feces, and there may be intestinal pathogens. Therefore, the number of coliforms (or coliform values) is often used as a hygienic standard for drinking water and food (or drugs). (The state stipulates that the number of E. coli in drinking water should not exceed 3). The antigenic composition of E. coli is complex and can be divided into bacterial antigen (O), flagellar antigen (H) and surface antigen (K). Resistance to body phagocytosis and anti-complement. According to the difference of bacterial antigens, E. coli can be divided into more than 150 types, of which 16 serotypes are pathogenic Escherichia coli, which often causes epidemic diarrhea and adult pleurisy. E. coli is an important material for studying microbial inheritance. For example, localized transduction was discovered in E. coli K12 strain in 1954. Lederberg experimented with two strains of auxotrophs of E. coli, laying the foundation for the study of bacterial bonding methods and genetic engineering. E. coli is the most important and most abundant type of bacteria in the gut of humans and many animals, mainly in the large intestine. When it invades some parts of the body, it can cause infections such as peritonitis, cholecystitis, cystitis and diarrhea. The symptoms of humans after infection with E. coli are stomach pain, vomiting, diarrhea and fever. The infection can be fatal, especially for children and the elderly. E. coli is a representative strain of the genus Escherichia. Generally, it does not cause disease. It is a resident bacteria in the intestines of humans and animals. Under certain conditions, it can cause intestinal infection. Some serotype strains are highly pathogenic and cause diarrhea, collectively known as pathogenic E. coli. The bacteria are more resistant to heat than other enterobacteria, and some bacteria survive after being heated at 55 ° C for 60 minutes or 60 ° C for 15 minutes. It can survive for weeks to months in natural water and last longer in lower temperature feces. Bile salts, brilliant green and the like have an inhibitory effect on Escherichia coli. Sensitive to sulfonamides, streptomycin, chloramphenicol, etc., but susceptible to drug resistance, is obtained by transfer of a plasmid with R factor. main feature Escherichia coli is the most important and most abundant type of bacteria in the intestines of humans and many animals. It is a flagellum that can move and has no spores. Mainly living in the large intestine. 1. Escherichia coli is a bacterium that belongs to prokaryotes; it has a cell wall composed of peptidoglycan, which contains only simple organelles of ribosomes, and no nuclei in the nucleus; plasmids in cytoplasm are often used as carriers in genetic engineering. 2. The metabolic type of E. coli is a heterotrophic anaerobic type. 3. The relationship between the human body and E. coli: in the case of no disease (under normal conditions), it can be considered as mutual benefit (usually considered to be this relationship in the high school stage); in the case of disease, it can be considered as parasitic. 4. The medium is added with Eosin and Blue, and the colonies are dark purple and have a metallic luster to identify the presence or absence of E. coli. 5. Application of Escherichia coli in biotechnology: Escherichia coli is the host of exogenous gene expression, with clear genetic background, simple technical operation, simple culture conditions and large-scale fermentation economy, which are highly valued by genetic engineering experts. At present, E. coli is the most widely used and most successful expression system, and is often the preferred system for efficient expression. 6. The status of E. coli in the ecosystem, if it lives in the large intestine, belongs to consumers, if it lives outside the body is a decomposer. 7. Its genomic DNA is a circular molecule in the nucleus. There may be multiple circular plasmid DNAs at the same time. 8. The pseudonucleus of E. coli cells has a DNA molecule of about 4 700 000 base pairs in length and about 4 400 genes distributed on the DNA molecule. The average length of each gene is about 1 000 bases. Correct. 9. The metabolic type of E. coli is a heterotrophic anaerobic type. E.coli Escherichia coli is a kind of bacteria that is closely related to our daily life. The scientific name is "Escherichia coli", which belongs to one of the major classes of enterobacteria. It is a single-celled organism that is parasitic in the human large intestine and harmless to the human body. It has a simple structure, rapid reproduction and easy cultivation. It is a biologically important experimental material. Within a few hours of the baby's birth, E. coli settled in the intestines after swallowing. Under normal circumstances, most E. coli are very self-sufficient, they will not bring any harm to our health, but also competitive to resist the attack of pathogenic bacteria, while also helping to synthesize vitamin K2, and the human body is Mutually beneficial symbiotic relationship. Only in special circumstances such as reduced immunity and long-term lack of irritation in the intestines, these good people in the week will make waves and move to places other than the intestines, such as the gallbladder, urethra, bladder, and appendix, causing infection in the corresponding parts. Or a systemic disseminated infection. Therefore, most E. coli is often seen as an opportunistic pathogen. Pathogenic nature 1. Colonization factor (CF): also known as Adhesin, the pili of E. coli. The pathogenic E. coli must first adhere to the intestinal wall of the host to avoid intestinal peristalsis and intestinal secretions. The colonization factors for human diarrhea are CFAI, CTAII (Colonization factorantigen I, II), and the colonization factor has strong immunogenicity and can stimulate the body to produce specific antibodies. E. coli has many virulence factors, including endotoxin, capsule, sputum secretion system, adhesin and exotoxin. (The sputum-type secretion system is a bacterial effect system that delivers toxic gene products to eukaryotic target cells. It consists of more than 20 proteins.) 2, Adhesin can make bacteria adhere to the cells of the urinary tract and intestines, to avoid the urine scouring during urination and the use of intestinal motility. E. coli adhesins are characterized by high specificity. Including: colonization factor antigen 〡, 〢, 〣; accumulation of adhesion pilom and sputum; bundle forming pili; tight adhesin; P pili; invasion of plasmid antigen protein and Dr pili. 3, exotoxin E. coli can produce a variety of exotoxins, including: Shiga toxin 〡 and 〢; heat-resistant enterotoxin 〡 and 〢; heat-labile enterotoxin 〡 and 〢. In addition, hemolysin A plays an important role in diseases caused by urinary pathogenic Escherichia coli. 4. Enterotoxin: It is an exotoxin released during the growth and reproduction of enterotoxic Escherichia coli. It is divided into heat-resistant and heat-labile. Heat labile enterotoxin (LT): heat Unstable, inactivated at 65 ° C for 30 minutes. It is a protein with a large molecular weight and is immunogenic. It consists of two subunits, A and B. A is further divided into A1 and A2, of which A1 is the active part of the toxin. After the B subunit binds to the GM1 ganglioside receptor on the surface of the intestinal mucosal epithelial cell membrane, the A subunit crosses the cell membrane and acts with adenylate cyclase to convert intracellular ATP into cAMP. When cAMP is increased, it causes excessive secretion of intestinal fluid, which exceeds the absorption capacity of the intestine and causes diarrhea. The immunogenicity of LT is similar to that of Vibrio cholerae enterotoxin, and the antiserum of both is cross-neutralizing. Heatstable enterotoxin (ST): stable to heat, not destroyed at 100 ° C for 20 minutes, small molecular weight, immunogen Lighted Mirror With Organizer Tray
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