Identification of Escherichia Coli

Introduction 

Bacteria affect various aspects of human beings, therefore, knowing their identities, sources, modes of actions, and impacts can help us to treat the diseases they cause to human beings (Leimbach, Hacker &Dobrindt , 2013). Identification of bacteria is made in the laboratories using various methods. The purpose of this experiment and report is to identify Escherichia coli from a sample provided in the laboratory using different means of identification. This paper is categorized into subheadings for easy analysis; introduction, the procedures used, the results of the experiment, discussion, and conclusion. The Escherichia Coli is a bacterium that is mostly found in the human intestinal tract and thrives in optimum temperatures of 30 degrees to 37degrees Celsius. 

Materials and Methods 

A sample containing the strains of unknown bacteria was provided labeled 123. The sample included strains of unknown gram-negative and gram-positive bacteria. Techniques of identifying both grams positive and gram-negative bacteria were applied to isolate the two types of bacteria and develop pure cultures of both bacteria. The first pure culture was obtained by performing the streaking method on the nutrient agar plate following the laboratory manual that was provided. The nutrient agar plate was then placed in the incubator to grow the pure cultures of the bacteria. After the growth of the bacteria after three days, a second streaking and incubation were done to obtain pure cultures of the strains of gram-negative and gram-positive bacteria. Then the gram stain test was done to isolate the gram-positive strains from the unknown gram-negative strains of bacteria present in the broth following the procedure from the lab manual. Then, a gelatin agar test was done to determine the production of gelatinase enzyme. There was no gelatinase enzyme produced by the gram-negative bacteria; there was no notable color change. 

The lactose test was then done to detect the presence of gram-negative bacteria. The lactose test aimed to identify the presence of fermentation that leads to the production of acid. The inoculums was inoculated into lactose fermentation tube. After some time the broth turned red and then to yellow which means acid was produced. Simmons citrate test was then done to confirm if the bacterium still in the medium could use citrate as its source of energy. The inoculums were then streaked on the Simmons citrate agar and inoculated for two days. The Simmons agar remained green meaning there was no reaction. For verification purposes to determine the presence of a gram-negative bacteria , a nitrate test followed. The purpose of the nitrate test was to determine if the nitrate was reduced to nitrite. A reagent containing nitrate was added to the broth which did not have any notable reaction; the color did not change to red. 

Results 

This list identifies the results of all the tests performed on the unknown gram-negative bacteria. 

Table 1 lists the test, purpose of test, reagents or media, observations, and results. 

Table 1. Gram-negative unknown tests 

Among the three tests done on the broth, Gram stain identified the presence of four gram-positive bacteria and one gram-negative bacteria. The list below determines the test performed on the unidentified gram-positive specimen. 

Table 2 lists the test, purpose of test, reagents, observations, and results 

Table 2. Gram-positive unknown tests 

The three tests performed to identify the gram-negative bacteria were; Gram Stain Test, Simmons Citrate Test, and Lactose Test. 

Discussion and Conclusion 

Crystal violet stain is first used to stain the bacteria cells, followed by a sequence of tests to eliminate the loosely bound purple stains. Then a second stain called safranin is used to stain the bacteria cells. Then, a gelatin agar test is done to determine the production of gelatinase enzyme (McNally et al ., 2013) . There was no gelatinase enzyme produced, which suggests that the bacteria present is gram-negative. The lactose test is then done to spot the possible existence of gram-positive bacteria. The broth turned red and then to yellow which means acid was produced. This eliminated the bacterium Proteus vulgaris which is a gram-positive bacteria. Simmons citrate test is then done to confirm if the bacterium could use citrate as its source of energy. The Simmons agar remained green meaning there was no reaction. This test eliminated Enterobacteraerogenes and Klebsiella pneumonia bacteria for the bacteria that were known. The only bacteria that was left from the tests performed were Escherichia coli . For verification purposes to determine the presence of E. coli, a nitrate test followed. The purpose of the nitrate test was to determine if the nitrate was reduced to nitrite. The four-gram positive bacteria identified from the tests were; Pseudomonas aeruginosa , Proteus vulgaris,Enterobacteraerogenes , and Klebsiella pneumonia. 

However, the experiment had disparities which were caused by human errors in a laboratory: Firstly; the cultures were left in the open air for too long which caused contamination, and secondly; the apparatus used were not well sterilized. On the next experiment to obtain the right results, all the laboratory rules and regulations would be followed 

There are numerous species of bacteria on earth; some are found on the earth surface, some in the layers of the earth, some on external bodies of other organisms, some in the internal parts of the bodies of other organisms, while others are found on the air ( Leimbach et al ., 2013) . There are both harmful and beneficial bacteria. For instance, E. coli is located in the human intestines and is beneficial in the process of digestion. Many bacteria affect various aspects of human life, therefore, knowing their identities, sources, modes of actions, and impacts can help us to treat the diseases they cause to human beings (Schieber, 2015) . For instance, E. coli has been proven to be clinically significant in human life in many ways. They help in digestion and absorption of nutrients (Chakababa et al ., 2013). Consequently, E. coli has a negative influence on human life like causing urinary tract infection and neonatal meningitis, especially in infants. Urinary tract infections and neonatal meningitis are treated through antibiotic therapy by administering ampicillin. 

References 

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Leimbach, A., Hacker, J., &Dobrindt, U.(2013) . E. coli as an all-rounder: the thin line between commensalism and pathogenicity. Curr. Top. Microbiol. Immunol. 358 , 3–32 

McNally, A. Cheng, L., Harris, S. R. &Corander, J. (2013). The Evolutionary Path to Extraintestinal Pathogenic, Drug-Resistant Escherichia coli Is Marked by Drastic Reduction in Detectable Recombination within the Core Genome, Genome Biology and Evolution , 5(4), 699–710. 

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