3 Tests To Identify Escherichia Coli

1443 words - 6 pages

In order to identify an unknown bacterium a variety of tests can be performed. The unknown bacterium that underwent a few of these tests was determined to be Escherichia coli. A Gram stain, citrate utilization test using Simmons citrate agar, and a urease detection test with phenol red were performed on the assigned bacterium. The unknown bacterium was determined to be E. coli because the tests concluded that the specimen was Gram-negative, bacilli, citrate utilization negative, and urease production negative. It is concluded that E. coli cannot utilize citrate as its sole carbon source and it cannot convert urea into ammonia and carbon dioxide.

Introduction
It is important in microbiology to be able to identify an unknown microorganism. Many tests that characterize functions of bacteria have been developed to accomplish this task. The unknown bacterium that was tested was discovered to be Escherichia coli. E. coli is a Gram-negative, bacillus bacterium. Gram-negative means there is an outer membrane surrounding the thin peptidoglycan layer of the cell. Bacillus means that the bacterium is rod-shaped. The E. coli was identified as Gram-negative and bacilli from performing a Gram stain. A Gram stain uses crystal violet for the primary dye and safranin as a counter stain (1). Gram-positive bacteria have a very thick peptidoglycan layer in their cell wall. This thick cell wall will stay stained purple by the crystal violet-iodine complex, and Gram-negative bacteria will be decolorized and stained pink from the safranin counter stain (1). The peptidoglycan layer’s thickness determines whether it is stained pink or purple.
To test an organism’s ability to use citrate as a source of carbon, a citrate utilization test is. This test is done by the use of Simmons citrate agar. A transport protein enzyme, citrate permease, is required to utilize citrate; an organism that does not produce citrate permease cannot utilize citrate as a carbon source. Sodium citrate is the only carbon source the medium contains, therefore if the organism cannot utilize citrate as a carbon source, it cannot convert the nitrogen source, ammonium dihydrogen phosphate, to ammonium and ammonium hydroxide (4). If the organism can use citrate as a carbon source, the ammonium compounds produced change the pH of the agar from neutral to alkaline, thus changing the color of the medium from green to deep blue. The deep blue color is produced by the pH indicator bromthymol blue included in the medium. Note that growth on the agar alone not accompanied by the change in color, does not indicate a positive test for citrate utilization because there is no evidence of the conversion of the nitrogen source to ammonium compounds (4).
Urease is an enzyme produced by some organisms that degrades urea to ammonia and carbon dioxide. To test an organism’s ability to produce the enzyme urease, a urease detection test is performed (2). The urease broth is a differential medium that contains urea,...

Find Another Essay On 3 tests to identify Escherichia coli

E. coli Traceability and Eradication Act: Protecting Consumer Health

2292 words - 9 pages ). Technological advances in agricultural business have brought forth factory farming and has become a popular technique to raise animals. However, factory farming creates problems, and one of the critical issues is the contamination of Escherichia coli also known as E. coli. The confined, concentrated, and unsanitary environment in factory farms causes animals to become prone to disease. Regardless of the animals' condition, they are sent to slaughterhouses

Escherichia coli Fact Sheet Essay

1137 words - 5 pages not have to be hospitalized and can reach full recovery at home. The recommended treatment for this infection is to drink lots of liquids and to get plenty of rest. Antibiotics should not be used to treat the symptoms of this infection. Taxonomy of the Species Domain: Bacteria Kingdom: Bacteria Phylum: Proteobacteria Family: Enterobacteriaceae Class: Gamma Proteobacteria Genus: Escherichia Order: Escherichia Species: Escherichia coli (E

E Coli and Salmonella in Swine Finishing Barns

2973 words - 12 pages Infect Dis. 2009 Jul 1;49(1):132-41. 2. Mollenkopf DF, Weeman MF, Daniels JB, Abley MJ, Mathews JL, Gebreyes WA, and Wittum TE. Variable within- and between-herd diversity of CTX-M cephalosporinase-bearing Escherichia coli isolates from dairy cattle. Appl Environ Microbiol. 2012 Jul;78(13):4552-60. 3. Doi Y, Paterson DL, Egea P, Pascual A, López-Cerero L, Navarro MD, Adams-Haduch JM, Qureshi ZA, Sidjabat HE, and Rodríguez-Baño J. Extended-spectrum

E. Coli (escherichia coli)

865 words - 3 pages intensive care, the average death rate is 3 - 5%. Antidiarrheal agents, such as loperamide, should be avoided.What can be done to prevent the illness?Always wash hands (using proper scrubbing techniques), shower often and take care of personal hygiene. Never eat undercooked or even pinkish meat (ground beef, hamburger etc.). Contaminated meat is the easiest and most common way to be infected by E. coli.E. coli will continue to be a public health

Escherichia Coli Absorbancy of Green Florescent Protein through Heat Shock

1459 words - 6 pages not enough to cause a necessary mutation. Among other techniques, heat shock can be used to help the acceptance of the plasmid by the bacteria. The amount of Escherichia Coli (Dh5α) transformed with the Green Florescent Protein Plasmid (pGFPuv) is quite low with the current temperature. The heat shock temperature used could be optimized to create a better acceptance rate of the plasmid.There are many different strains of GFP. The original

Escherichia coli 0157:H7

1052 words - 4 pages . Entry, Spread and Multiplication: After food contaminated with E. coli 0157:H7 is ingested, it travels through the digestive system and attaches to the mucosal epithelial cells of the large intestine and forms a pedestal, which leads to destruction of the microvili. The bacteria will then multipy and produce toxins, which, in addition to diarrhea cause vomiting in 50% of cases and fever in 30%. The average incubation period is 3-4 days

Bacteria and Antibiotic Lab Write Up

1344 words - 5 pages antibiotic against Bacillus cereus. It only killed an eleven millimeter diameter circle of Bacillus cereus, as opposed to most other antibiotics tested against Bacillus cereus, which killed an average of about twenty five millimeter diameter circles. Penicillin was less than half as effective against Bacillus cereus than most other antibiotics. However, Penicillin was more effective against Bacillus cereus and Escherichia coli, than Micrococcus luteus

Bacteria Lab Report

1750 words - 7 pages , erythromycin does not necessarily kill the bacteria, but leaves them unable to replicate. The remaining bacteria are incapable of surviving and are destroyed by the immune system.The three different pathogens, Escherichia coli, Shigella flexneri, and Staphylococcus aureus were exposed by Erythromycin and the effects were examined.Escherichia coli (E. coli), a prokaryote with one circular chromosome composed of monocistronic (single genes) and

The Human Genome Project

478 words - 2 pages The Human Genome ProjectThe Human Genome Project is a 13-year project started in 1990 and coordinated by the U.S. Department of Energy and the National Institutes of Health. The project originally was planned to last 15 years, but rapid technological advances have accelerated the expected completion date to 2003. Project goals are to·identify all the approximate 30,000 genes in human DNA,·determine the sequences of the 3 billion

Identifying Two Unknown Species of Bacteria

1353 words - 5 pages citrate it produces carbon dioxide that reacts with sodium and water, also found in the medium, to produce sodium carbonate. Sodium carbonate elevates the pH causing a color change from green to blue (a positive result). The second bacterium was gram positive. There are three tests that are used to identify gram positive bacteria. The three tests are hemolyses on blood agar, Mannitol fermentation on mannitol salt agar, and the coagulase test

Prokaryotic Cells

1905 words - 8 pages appearance. It was allowed to air dry. After that by using forceps slide "E" was fixed in burner flame by using heat fix method. Above procedure was repeated for slide "S". Only difference was instead of "Escherichia .coli" culture for Slide "S" a culture of "Staphylococcus aureus" bacteria was used. Slides "S" and "E" were handled by forceps. A solution of gram's crystal violet

Similar Essays

Qualitative Tests For Carbonyls: Aldehydes Vs. Ketones. Various Chemical Tests Identifying Ketones And Aldehydes Are Used In This Experiment In Order To Identify An Unknown Carbonyl Compound.

1040 words - 4 pages Laboratory #6Qualitative Tests for Carbonyls: Aldehydes vs. KetonesIntroductionVarious chemical tests identifying ketones and aldehydes are used in this experiment in order to identify an unknown carbonyl compound. The tests used are: 2,4-dinitrophenylhydrazone test, Tollen's Test, Benedict's Test, Chromic Acid Test, aka Bordwell-Wellman Test, Schiff's Test, and Iodoform Test. These classification tests provide results based on color change or

Decision Making Identify And Describe A Minimum Of 3 Problems, Relating To Decision Making That Occur When Managers Complete Performance Reviews

877 words - 4 pages When managers and supervisors perform employee's performance appraisal/performance evaluations it has come to my attention that they are being inconsistent in the way they rate or evaluate employees. This could jeopardize our performance appraisal program. The problems I found can be rectified very easily and need to be taken care of as soon as possible. One of the problems I found was many managers and supervisors are affected by the halo

Esherichia Coli Essay

1401 words - 6 pages plate and the plate is then examined for evidence of beta-hemolysis and for a zone of inhibition around a bacitracin disk that is placed on the blood agar plate. Some bacteria will not grow due to antibiotic susceptibility and where beta hemolysis occurs there will be a cleared area around the bacteria. The unknown bacterium 48 was determined to be Escherichia coli. As determined by the testing done on the bacteria, the bacterium is a gram

Fundamentals Of E. Coli Essay

1538 words - 7 pages Contents  Introduction  History  Characteristics  Mechanism of action  Factors affects growth  Toxins  Symptoms  Transmission  Complications  Outbreaks  Food Association  Diagnosis  Disinfetants  Trearment  Vaccination  Preventions  References Enterohemorrhagic Escherichia coli Introduction E.coli is a gram negative bacteria present in