Category Archive Escherichia coli gram stain


Escherichia coli gram stain

Commonly referred to as E. While most of the strains are harmless and also important in the human intestinal tractothers are harmful and can cause very serious health implications. A good example of this is E coli H7. Apart from food poisoning that can cause diarrhea and other problems in the digestive system, harmful strains of E coli can cause the following health problems.

In the intestinal tract, E coli plays an important role in that it aids in digestion and supports the absorption of vital vitamins from food in the body. In addition, it has been shown to be beneficial in that it prevents the growth and proliferation of other harmful species of bacteria that would otherwise cause health problems.

This is because they stain negative using the Gram stain. The Gram stain is a differential technique that is commonly used for the purposes of classifying bacteria. The staining technique distinguishes between two main types of bacteria gram positive and gram negative by imparting color on the cells.

escherichia coli gram stain

Being Gram-negative bacteria, E. The presence lipopolysaccharides on the outer membrane of bacteria gives it an overall negative charge to the cell wall.

Because of these properties, E. See page explaining Gram positive and Gram negative bacteria. To determine whether a strain s is present in a sample, it's necessary to stain the sample. Here, Gram stain is used as it helps distinguish between the gram positive and gram negative bacteria in a sample.

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Being a differential stain, Gram stain is more complex compared to more simple stains like methylene blue. As such, more than one stain is used for the purposes of differentiating the its cellular components. For this technique, 3 different stains are used. These include:.

Smear Preparation. Here, heat is used for fixing. Heat fixing procedure involves the following steps:. Gram Staining. When viewed under the microscope, Gram-negative E.

Escherichia Coli (E. Coli): Meaning, Morphology and Characteristics

Coli will appear pink in color. The absence of this of purple color is indicative of Gram-positive bacteria and the absence of Gram-negative E. The hanging drop method refers to a technique that helps examine small, living and unstained organisms. It can be used for such motile bacteria as Ps. Using the hanging drop technique is also very important given that it helps distinguish between Brownian movement the movement of particles that are suspended in a fluid and motility of microorganisms.

Some of the requirements include:. To determine whether the bacteria is really moving, it's important to ensure that it's moving in different directions and changing position. This differentiates motility of the organism from mere Brownian motion. Return from E. Coli under the Microscope to MicroscopeMaster Home. Chris Hayhurst E. Dr Kaiser, G. February In this article we will discuss about Escherichia Coli E.

Coli :- 1. Meaning of Escherichia Coli 2. Morphology and Staining of Escherichia Coli 3. Cultural Characteristics 4. Biochemical Reaction 5. Antigenic Structure 6. Toxin 7. Haemolysin 8. Infection: E. Coli Causes 9.

escherichia coli gram stain

Antigenic Typing Laboratory Diagnosis Treatment Medical Importance. Detection of E. It is motile by peritrichous flagellae, though some strains are non-motile. Spores are not formed.

Capsules and fimbriae are found in some strains.

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It is an aerobe and a facultative anaerobe. On Nutrient agar, colonies are large, thick, greyish white, moist, smooth, opaque or translucent discs. The smooth s form seen in fresh isolation is easily emulsified in saline, whereas the rough R form often auto agglutinates in saline. On MacConkey agar medium, colonies are bright pink due to lactose fermentation. On selective media Desoxycholate citrate agar-DCA; salmonella shigella-SS medium used for the isolation of salmonella, their growth is inhibited, however their colonies are pink on DCA as it contains lactose and neutral red.

In broth, there is generalized turbidity and deposit which disperses on shaking.

Bacteria under the Microscope (E. coli and S. aureus)

Glucose, lactose, mannitol, maltose are fermented with acid and gas production, but sucrose is not fermented by typical strain of E. In Triple sugar iron TSIacid and gas are produced. K antigen is an envelope antigen, which encloses the O antigen, renders the strain inagglutinable by the O antiserum and contributes to virulence by inhibiting phagocytosis.

It may be of three types —L, A and B. Though L type is common, the B antigen is medically important as it is found on enteropathogenic E. The F antigen has no significance in antigenic classification of E. Type I fimbriae mediates adhesion of bacterium to human and animal cells. Such adhesion enhances bacterial pathogenicity e. Several fibrin structures resembling fimbriae have been demonstrated.

They, most probably, play a very important role in pathogenesis of diarrhoeal diseases and urinary tract infection. Besides the endotoxin associated with O antigen, some strains produce two types of exotoxin—enterotoxin and haemolysin.

Enterotoxins responsible for diarrhoea are of two types—heat labile LT ; heat stable ST. LT is similar to cholera enterotoxin antigenically and in its mechanism of action—by stimulating the adenyl cyclase—cyclic adenosine monophosphate cAMP system to produce fluid accumulation in the intestinal lumen.

ST appears to stimulate fluid secretion into the gut through the mediation of cyclic guanosine monophosphate cGMP resulting into dehydration.Four different strains of Escherichia coli on Endo agar with biochemical slope see here. Glucose fermentation with gas productionurea and H 2 S negativelactose positive with exception of strain D - " late lactose fermenter "; on Endo agar it looks like lactose negative. All four strains are mannitol positive best seen in fig.

Dcellobiose negative strains A, B. Colonies of some strains have typical greenish metallic sheen fig. E but many of them grow without it fig. Escherichia coli commonly abbreviated E. Most E. The harmless strains are part of the normal flora of the gutand can benefit their hosts by producing vitamin K2, and by preventing the establishment of pathogenic bacteria within the intestine.

Certain strains of E. Food poisoning caused by E. OH7 is also notorious for causing serious and even life-threatening complications such as hemolytic-uremic syndrome.

The OH4 strain is equally virulent. It is the strain behind the deadly June E. Enteric E. Abbreviated from Wikipedia. Escherichia coli Four different strains of Escherichia coli on Endo agar with biochemical slope see here.

Gastrointestinal infection Certain strains of E. Basically, the urinary tract comprises the parts of the body responsible for the removal of body waste and excess water, and the maintenance of electrolyte balance in the body.

Escherichia coli O157:H7

The urinary tract includes the kidneys, the bladder, the urethra and the ureters. Causes of UTIs Naturally, the urinary system is immune to infections; therefore, certain microorganisms must invade it before it can be infected. In ascending infections, fecal bacteria colonize the urethra and spread up the urinary tract to the bladder as well as to the kidneys causing pyelonephritisor the prostate in males.

Because women have a shorter urethra than men, they are more likely to suffer from an ascending UTI. Escherichia coli are the main causative bacteria of UTIs ; they are responsible for 4 out of 5 cases of the infections. Uropathogenic E.The bacterium grows massively in fresh fecal matter under aerobic conditions for 3 days, but its numbers decline slowly afterwards. Cells are able to survive outside the body for a limited amount of time, which makes them potential indicator organisms to test environmental samples for fecal contamination.

The bacterium can be grown and cultured easily and inexpensively in a laboratory setting, and has been intensively investigated for over 60 years. Under favorable conditions, it takes as little as 20 minutes to reproduce. During the staining process, E. The outer membrane surrounding the cell wall provides a barrier to certain antibiotics such that E.

Strains that possess flagella are motile. The flagella have a peritrichous arrangement. Since many pathways in mixed-acid fermentation produce hydrogen gas, these pathways require the levels of hydrogen to be low, as is the case when E.

In addition, E. In other words, this obligate heterotroph's metabolism can be altered to display autotrophic capabilities by heterologously expressing carbon fixation genes as well as formate dehydrogenase and conducting laboratory evolution experiments. This may be done by using formate to reduce electron carriers and supply the ATP required in anabolic pathways inside of these synthetic autotrophs.

Although the EDP is the more thermodynamically favorable of the three pathways, E. The EDP mainly remains inactive except for during growth with gluconate.

When growing in the presence of a mixture of sugars, bacteria will often consume the sugars sequentially through a process known as catabolite repression. By repressing the expression of the genes involved in metabolizing the less preferred sugars, cells will usually first consume the sugar yielding the highest growth rate, followed by the sugar yielding the next highest growth rate, and so on. In doing so the cells ensure that their limited metabolic resources are being used to maximize the rate of growth.

The well-used example of this with E. Catabolite repression has also been observed in E. Optimum growth of E. Growth can be driven by aerobic or anaerobic respirationusing a large variety of redox pairsincluding the oxidation of pyruvic acidformic acidhydrogenand amino acidsand the reduction of substrates such as oxygennitratefumaratedimethyl sulfoxideand trimethylamine N-oxide.

It uses oxygen when it is present and available. It can, however, continue to grow in the absence of oxygen using fermentation or anaerobic respiration. The ability to continue growing in the absence of oxygen is an advantage to bacteria because their survival is increased in environments where water predominates. The bacterial cell cycle is divided into three stages. The B period occurs between the completion of cell division and the beginning of DNA replication.

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The C period encompasses the time it takes to replicate the chromosomal DNA. The D period refers to the stage between the conclusion of DNA replication and the end of cell division. However, the length of the C and D periods do not change, even when the doubling time becomes less than the sum of the C and D periods. At the fastest growth rates, replication begins before the previous round of replication has completed, resulting in multiple replication forks along the DNA and overlapping cell cycles.

The number of replication forks in fast growing E. This only happens if replication is initiated simultaneously from all origins of replicationsand is referred to as synchronous replication.

However, not all cells in a culture replicate synchronously. In this case cells do not have multiples of two replication forks.

Replication initiation is then referred to being asynchronous. The process of transduction, which uses the bacterial virus called a bacteriophage[33] is where the spread of the gene encoding for the Shiga toxin from the Shigella bacteria to E. Genome sequencing of many isolates of E. However, this has not been done, largely due to its medical importance, [34] and E.

In fact, from the more constructive point of view, the members of genus Shigella S. A strain is a subgroup within the species that has unique characteristics that distinguish it from other strains.Escherichia coli E.

A pathogenic strain of E. Escherichia coli OH7 was first identified as a human pathogen in in the United States of America, following an outbreak of bloody diarrhea associated with contaminated hamburger meat.

Inthere was an outbreak involving raw spinach, with illnesses, hospitalizations, 31 hemolytic uremic syndrome, a severe kidney condition, and three deaths in the US 1. Prevention of E. Lastly, avoid raw milk, unpasteurized dairy products, and unpasteurized juices; and avoid swallowing water when swimming or playing in lakes, ponds, streams, and swimming pools 1.

The complete sequence of the OH7 chromosome is 5, bp in length. Since the strain contains a large virulence plasmid of 92, bpm and a cryptic plasmid of bp the whole genome size is 5,bp 4. Some strains are piliated and capable of accepting and transferring plasmid to and from other bacteria 1. Though it has extremely simple cell structure, with only one chromosomal DNA and a plasmid, it can perform complicated metabolism to maintain its cell growth and cell division.

The strain also possesses a glutamate-fermentation system and two aromatic acid degradation systems that are not present in E. Escherichia coli can be commonly found in lower intestines of human and mammals and help with digestion processes.

However, different strains of E. The Shiga toxin released from E. Shiga toxin is the main virulence factor of E. Shiga toxin released from E. Shiga toxin targets an organ such as the kidney and binds to receptors on cell membranes. Shiga toxin enters cells and stops the cells from producing proteins it needs to function. Without the ability to sustain its function, the cell dies through either apoptosis or necrosis.

escherichia coli gram stain

By killing cells crucial for organ function, Shiga toxins can have a debilitating effect on the body 5. Implicated foods are typically those derived from cattle e. Some important symptoms are bloody diarrhea, stomach cramping, vomiting, and loss of appetite, abdominal pain, and fever and kidney failure. Infection with E. According to CDC, in E. Right now there has been only seven cases of E.

Escherichia coli Oh7 and other shiga toxin-producing Escherichia coli stec. Escherichia coli OH7. NCBI taxonomy browser. Hayashi, T. Complete genome sequence of enterohemorrhagic Escherichia coli Oh7 and genomic comparison with a laboratory strain k DNA Research, 8, 11— Shiga toxin translocation across intestinal epithelial cells is enhanced by neutrophil transmigration. Infect Immun.Her picture even shows her eating food at a restaurant.

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escherichia coli gram stain

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Meztishura Posted on10:12 pm - Oct 2, 2012

Sie halten unbedeutend?