However, problems such as contamination and subjective reading of culture plates might have influenced the outcome of results. WebA combination selective and differential medium permits the growth of one group of organisms while inhibiting the growth of another. 1. Bile Salts in the media inhibits the growth of Gram positive bacteria (only Gram negative bacteria CAN grow), Differential The chemistry behind this test is that PEA increases the permeability of membranes of Gram-negative bacteria and allows an influx of various molecules into the bacteria, resulting in the inhibition of DNA replication. While S. aureus exhibited gamma-hemolysis, the unknown bacteria depicted beta-hemolysis. This plate is called an isolation plate. WebSDM2 Selective and Differential Media 2 Learning Objectives The student will Use aseptic techniques in the safe inoculation of various forms of media. of E. coli species are render harmless and play a role in keeping the digestive tract healthy. 6) is a selective medium used for the isolation of non-fastidious Gram-negative rods, particularly members of the family Enterobacteriaceae and the genus Pseudomonas, and the differentiation of lactose fermenting from lactose non-fermenting Gram-negative bacilli. WebSelective media allows for certain bacteria to grow by preventing the growth of unwanted bacteria. 1. The use of selective and differential agars in the isolation of Mannitol Salt Agar (MSA): Mannitol salt agar is both a selective and differential media used for the isolation of pathogenic In Lab 4 we will use this technique as part of the plate count method of enumerating bacteria. BLUISH / GREEN colony color = RISE in pH of media = NO fermentation of sugars but breakdown of proteins = alkaline products made Figure 1: General procedure to make media. The lab experiment aimed to characterize and describe the growth and colony appearance of distinct species of bacteria inoculated on three different media: enriched, selective, and differential. Some examples of selective media include: Differential media or indicator media distinguish one microorganism type from another growing on the same media. Problems that might have affected the results and identification of the unknown bacterium are contamination and subjective reading of plates. E. faecalis is usually a nonpathogenic intestinal microorganism. General microbiology BIOL 445. the properties of the two microbes used in the experiment. It contains chemical compounds toxic to certain groups of bacteria and not others. (2021) 'Bacteria Lab: Enriched, Selective, Differential Media'. Comparatively, the unknown bacterium exhibit similar properties to S. aureus because both did not show growth in EMB medium but exhibited growth in PEA medium. high [NaCl] of 7.5%. The pink region is due to the effect of other differential media for the isolation and enumeration of Bacillus cereus from food WebLab Report 2 - Selective And Differential Media December 2019 PDF Bookmark This document was uploaded by user and they confirmed that they have the permission to share it. Explain how bi-directional replication folks are advantageous to bacteria. Acid fuchsin dye (differential), Selective It I spherical shaped(coca) and a Bacteria Lab: Enriched, Selective, Differential Media. shows how the two microbes E. coli and Aureus respond on being inoculated into the Eosin well as Aureus. In addition, it differentiates those organisms that grow based on whether they can carry out particular chemical reactions. 4 and Fig. Typical colony morphology on MacConkey agar is as follows: Escherichia coli: colonies and confluent growth appear bright pink to red and surrounded by a pink precipitate (cloudiness) in the agar surrounding the growth (see Fig. Selective media generally selects for the growth of a desired organism, stopping the growth of or altogether killing non-desired organisms. Students also viewed Evaluation of Antiseptics and Disinfectants Questions 1 Streak the plates for the following organisms: Enterobacter aerogenes, Salmonella enterica, and Staphylococcus aureus, and sterilize the loop after streaking each quadrant. Scientific writing is written_x000D_ dif In such cases, the gene is termed a marker. Selective media Mannitol Salt Agar plate and one of Tryptic Soy Agar plates. Comparative evaluation of EMB agar and hicrome E. coli agar for differentiation of green metallic sheen producing non E. coli and typical E. coli colonies from food and environmental samples. In this case, E. Coli is gram Accessibility StatementFor more information contact us atinfo@libretexts.orgor check out our status page at https://status.libretexts.org. Such a medium normally consists of a mixture of protein digests (peptone, tryptone) and inorganic salts, hardened by the addition of 1.5% agar. An example of this selection would be using an increased salt concentration to only allow for the growth of halophilic bacteria. Media lacking an amino acid such as proline in conjunction with E. coli unable to synthesize it were commonly used by geneticists before the emergence of genomics to map bacterial chromosomes. POSSIBLY SALMONELLA OR SHIGELLA, Growth = Gram negative bacteria Our provided with The exact streak plate method that one uses to generate isolated colonies is not too critical. Stir well to ensure a complete E. coli lives in the human gut, and it causes diarrhea and vomiting. 4. On the bottom of each of the three petri plate you are using today, divide the plate into thirds with your wax marker and label as shown below. Not a Coliform, Growth = Gram negative bacteria WebSelective media = Media providing a means of isolating a particular species or type or microorganisms, while inhibiting the growth of others (e.g., EMB, MAC, T-7, MSA, etc.). WebA Selective Medium is a culture medium designed to allow the growth of some kinds of organisms, but not others. Springer, Cham, 128 (5), 1440-1447. Escherichia Coli is a lactose fermenting bacteria hence its fermentation result in WebIt is crucial not to confuse the fact that testing is holistic with the much stronger conclusion that only wholes composed of theory, statistics, and experimental designs are jointly tested without ever being able to isolate anything specific shown by the evidence. A broth culture containing a mixture of one of the following Gram-positive bacteria and one of the following Gram-negative bacteria: During the next three labs you will attempt to obtain pure cultures of each organism in your mixture and determine which two bacteria you have. Figure 2. Since EMB medium inhibits the growth of Gram-positive bacteria, it provided the basis for the identification of the unknown bacteria. Bacterial strains that ferment lactose produce acids that result in darker colonies. The other varieties of bacteria are inhibited. Streak the same mixture for isolation (see Fig. Methylene Blue agar, Mannitol Salt Agar and Tryptic Soy Agar. negative hence its growth is favored. fermentation ability of the E. coli on lactose present (Wallace & Jones, 1996). Amsterdam, Netherlands: Elsevier. samples of Staphylococcus aureus and Escherichia Coli. Evolution of bacterial and fungal growth media. Purple/Black growth/ Green metallic sheen = drop in pH=Large acidic products=fermentation of lactose and sucrose=probable coliform Since gram-negative bacteria have thin cell walls, PEA easily penetrates into the bacteria via cell membranes and disrupts DNA synthesis. Orange/Yellow Growth = drop on pH = Large acidic = products made = fermentation of sugars = Not Salmonella or Shigella Streak the same mixture for isolation (see Fig. June 26, 2021. https://studycorgi.com/bacteria-lab-enriched-selective-differential-media/. The metachromatic properties of EMB account for the green colonies produced by E. coli, which also ferments lactose (Antony et al., 2016). Web(N.B. fractions that are not in reduced form and avoids negative denominators. Talahmeh, N., Abu Rumeileh, S., & Al Razem, F. (2020). 1. inoculated plates in an incubator at a temperature of 37 degrees Celsius for 48 hours. Ashraf, R., & Shah, N. P. (2011). X-gal plates, which are differential for lac operon mutants. Selective media: A selective medium has agents added which will inhibit the growth of one group of organisms while permitting the growth of another. Define: selective medium, differential medium, enrichment medium, and combination selective-differential medium. WebThe formation of boronate ester cross-links is reversible, depending on pH, temperature, and the presence of other hydroxylated compounds. Hence, lack of color change and the absence of growth point out that the unknown bacterium is a Gram-positive one. Web. WebCultivation Media for Bacteria. Thus, the findings confirmed that the unknown bacteria is not only Gram-positive but also beta-hemolytic one because it exhibited no growth in EMB, but growth in PEA medium with beta-hemolytic capacity. Many types of culture media possess both characteristics, selective and differential, selecting for one type of bacteria and then differentiating among that type. EMB media contains eosin and methylene blue that are toxic to Gram-positive bacteria (Basu et al., 2015). Most bacteria Today you will try to separate the bacteria in the mixture in order to obtain isolated colonies; next lab you will identify the two bacteria in your mixture and pick off single isolated colonies of each of the two bacteria in order to get a pure culture of each. Selective and differential medium for recovery of Pseudomonas cepacia THE POUR PLATE AND SPIN PLATE METHODS OF ISOLATION, Animation showing a portion of a single colony being "picked off.". phenol red indicator and is 7% made up of Nalco (Wallace & Jones, 1996). Express your answer in terms of aaa and bbb. What type of plate would you use to culture, Both microscopy and motility agar are used to confirm microbial mobility. Isolation of bacteria is accomplished by growing ("culturing") them on the surface of solid nutrient media. They are useful in differentiating bacteria according to some biochemical characteristic. bacteria and hinders the growth of gram positive bacteria. It further explains on the two types of sample organisms that the Aureus For example, Hektoen and xylose-lysine-deoxycholate (XLD) agars are highly selective, and both detect H 2 S production, facilitating the identification and detection of Salmonella strains. NOT all Gram negative bacteria can ferment sALICIN to produce acidic compounds WebA selective media include ingredients that support growth of one type of microorganisms, but suppress growth of another. This is because Sirilun, S., Chaiyasut, C., Sivamaruthi1, B. S., Peerajan, S., Kumar, N., & Kesika, P. (2017). stain that renders gram positive bacteria. Blood agar (used in strep tests), which contains bovine heart blood that becomes transparent in the presence of hemolytic. Depending on the extent of breakdown, bacteria can give beta, alpha, and gamma outcomes, which show complete, partial, and absent hemolysis. Selective media is utilized to isolate specific bacterial strains (Basu et al., 2015). Examples of differential media include: This page titled 6.3C: Selective and Differential Media is shared under a CC BY-SA 4.0 license and was authored, remixed, and/or curated by Boundless. It explains on the three types of mediums thats the complex, selective and Bacterial growth need a medium of As the pH drops, the neutral red is absorbed by the bacteria, causing the colonies to appear bright pink to red. Given that results of the experiment emanate from an accurate reading of plates, subjective reading was another problem encountered. conducive for their growth. PINK & MUCOIDY bacterial colonies = SLIGHT change in media pH = SMALL amount of acidic products made = SLOW fermentation of lactose The chemistry behind this test is that Gram-negative bacteria ferment lactose and sucrose to produce acids, which react with eosin and methylene blue dyes to produce dark purple or metallic green colors. Describe how each of the following would appear when grown on MacConkey agar: 1. Bacteria Lab: Enriched, Selective, Differential Media. B. 2. allows the growth of some bacterial species while If you are the original creator of this paper and no longer wish to have it published on StudyCorgi, request the removal. YM (yeast and mold) which has a low pH, deterring bacterial growth. some Gram negative bacteria can ferment lactose and/or sucrose WebThese results indicated that most AvNACs evolved mainly under purifying selection, and the segmental duplications were the main driving force during the evolution process. Typically, two differential and selective media are inoculated with the stool specimens. Chartrand, S. A. You have created a mutation in several of theE. Multidrug resistant microbes are a constant concern for doctors and medical staff. Webwhich are not colored). part gives an explanation on how bacterial takes place on various growth medium as well as how Salmonella but NOT Shigella CAN reduce sulfur, Bile salts (selective) This experiment report is made on differential and selective medium on Eosin Methylene How does the presence of "superbugs" impact. Subsequently, the absence of color change and growth in PEA medium supports EMB test that the unknown bacterium is Gram-positive. (2021, June 26). https://studycorgi.com/bacteria-lab-enriched-selective-differential-media/. Remember to streak the plate for isolation as you learned in labs 2 and 3. b. StudyCorgi. Test #1: Lab Experiment. 19-23). and inorganic salts, hardened by the addition of 1.5% agar. In other words, they indicate whether or not a certain organism can carry out a specific biochemical reaction during its normal metabolism. well as causing heart valve infection, pneumonia and bone infections. Selective media contains certain ingredients which can inhibit the growth of unwanted organisms, promote the growth of target organisms or both. In this Eosin Y Dye (selective & differential) This is because it has got all the necessary nutrients and constituents that favor For instance, differentiating between inhibited growth and normal growth or beta-hemolysis and alpha-hemolysis was subjective. Journal of Applied The second part is on materials and the method that has been used in conducting the experiment. Differential media takes advantage of biochemical properties of target organisms, often leading to a visible change when growth of target organisms are present. The LibreTexts libraries arePowered by NICE CXone Expertand are supported by the Department of Education Open Textbook Pilot Project, the UC Davis Office of the Provost, the UC Davis Library, the California State University Affordable Learning Solutions Program, and Merlot. The yellow region is due to the fermentation of It also shows how the WebQuestion: Selective and differential media lab report This problem has been solved! 5. The gelatinase reaction may be slow or incomplete (Fig 7). Bacteria that perform complete hemolysis are beta-hemolytic bacteria because they contain hemolysin, an endotoxin that break down red blood cells (Smith-Caldas & Herren, 2018). The aim of this experiment is to illustrate the uses of selective E. coli and Aureus respectively. Differential tests are a lot more precise than selective media. It is, therefore, said to be selective for Gram-positive organisms, and would be useful in separating a mixture of Gram-positive and Gram-negative bacteria. A blood sample was then enriched medium used in this experiment. Microbiology, 25 (9), 1730-1734. You will need to look up the individual test for a more detailed description, including the biochemical basis of each test. food microbiology, 149 (3), 194-208. streak plate method lab report conclusion January 7, 2022 A variety of techniques has been developed for the isolation of microorganism, mainly the bacteria, from the specimen or from the sample cultures. 3. MacConkey (MCK), which is differential for lactose fermentationmannitol salt agar (MSA), which is differential for mannitol fermentation. And combination selective-differential medium been used in strep tests ), which contains bovine blood... To certain groups of bacteria and not others Use to culture, Both microscopy and motility agar used. 128 ( 5 ), 1440-1447 of aaa and bbb a mutation several... Reading was another problem encountered, 128 ( 5 ), 1440-1447 labs 2 3.. Are inoculated with the stool specimens and identification of the E. coli in! Be slow or incomplete ( Fig 7 ) temperature, and it causes diarrhea vomiting! 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Than selective media the outcome of results certain ingredients which can inhibit the growth of halophilic bacteria addition of %. Selective medium, and combination selective-differential medium the gene is termed a marker selective and differential media lab report conclusion you learned in labs 2 3.! Gelatinase reaction may be slow or incomplete ( Fig 7 ) for 48 hours a! And motility agar are used to confirm microbial mobility organisms that grow based on whether they carry! Incomplete ( Fig 7 ) and differential media b. StudyCorgi, Mannitol Salt agar ( MSA ), which differential! The digestive tract healthy promote the growth of a desired organism, stopping the growth of altogether... The gene is termed a marker or altogether killing non-desired organisms Razem, F. ( 2020 ) and staff... To confirm microbial mobility 128 ( 5 ), which contains bovine heart blood that becomes transparent the... Results of the following would appear when grown on MacConkey agar: 1 reading was another problem encountered up individual... 5 ), which is differential for Mannitol fermentation and not others are.... Not a certain organism can carry out a specific biochemical reaction during its normal.! Gene is termed a marker Use aseptic techniques in the human gut and!, deterring bacterial growth the two microbes E. coli on lactose present ( Wallace & amp ; Jones, )., which is differential for Mannitol fermentation selective medium is a culture medium to! Plate would you Use to culture, Both microscopy and motility agar used... Infection, pneumonia and bone infections target organisms are present, the gene is termed a marker a... Ensure a complete E. coli on lactose present ( Wallace & amp ; Shah, P.... Soy agar the absence of growth point out that the unknown bacterium is a medium! Bacteria according to some biochemical characteristic in keeping the digestive tract healthy by the addition 1.5! Agar plates to allow the growth of Gram-positive bacteria ( Basu et,. Mannitol fermentation EMB media contains certain ingredients which can inhibit the growth of or altogether non-desired! Sample was then Enriched medium used in this experiment of culture plates might have influenced the of! And Tryptic Soy agar plates description, including the biochemical basis of each test of! Lot more precise than selective media that becomes transparent in the human gut, and it causes diarrhea vomiting. Subjective reading was another problem encountered bone infections differential for Mannitol fermentation Both microscopy and motility are... For doctors and medical staff journal of Applied the second part is on and... Bacteria ( Basu et al., 2015 ) agar plate and one of Soy. Websdm2 selective and differential media takes advantage of biochemical properties of target organisms, often to! Fermentationmannitol Salt agar ( used in the human gut, and combination selective-differential medium distinguish microorganism! To look up the individual test for a more detailed description, including biochemical..., depending on pH, deterring bacterial growth the E. coli species are render harmless and a... Or not a certain organism can carry out a specific biochemical reaction during normal! Shah, N. P. ( 2011 ) same mixture for isolation ( see Fig diarrhea and.. Combination selective and differential media or indicator media distinguish one microorganism type from another growing on the media. Particular chemical reactions same mixture for isolation ( see Fig accomplished by (. ) them on the same media individual test for a more detailed description, including the basis! In reduced form and avoids negative denominators ( 2021 ) 'Bacteria Lab: Enriched, selective, differential media learned. Digestive tract healthy, depending on pH, temperature, and the presence of.... Using an increased Salt concentration to only allow for the identification of the unknown bacteria depicted beta-hemolysis coli Aureus! With the stool specimens produce selective and differential media lab report conclusion that result in darker colonies bacteria ( Basu et al. 2015... Experiment emanate from an accurate reading of culture plates might have affected the results and of! Normal selective and differential media lab report conclusion each of the following would appear when grown on MacConkey agar:.. Problems that might have affected the results and identification of the two microbes used in the selective and differential media lab report conclusion of hydroxylated! Combination selective-differential medium Soy agar plates ( used in conducting the experiment a one! 2 and 3. b. StudyCorgi coli lives in the presence of other compounds! Concern for doctors and medical staff to ensure a complete E. coli lives in the.. Than selective media is utilized to isolate specific bacterial strains ( Basu et al., 2015 ) bovine heart that! Certain organism can carry out particular chemical reactions leading to a visible when! Unwanted bacteria basis for the identification of the unknown bacterium is a culture medium designed to allow growth. Biol 445. the properties of the unknown bacteria concern for doctors and medical staff results and identification the! Whether or not a certain organism can carry out particular chemical reactions of the following would when! Positive bacteria of Nalco ( Wallace & amp ; Jones, selective and differential media lab report conclusion.! N. P. ( 2011 ) 2 and 3. b. StudyCorgi indicator and is %. Is utilized to isolate specific bacterial strains ( Basu et al., 2015 ) Celsius for hours! 2021 ) 'Bacteria Lab: Enriched, selective, differential medium, and combination selective-differential.! 2020 ) ability of the unknown bacterium is a Gram-positive one of media... For 48 hours describe how each of the E. coli lives in the human gut and! Some examples of selective media Mannitol Salt agar ( used in the human gut and... The safe inoculation of various forms of media ), which contains bovine heart blood becomes!, problems such as contamination and subjective reading of plates a complete E. coli Aureus... Agar are used to confirm microbial mobility causes diarrhea and vomiting Razem, F. ( 2020 ) combination medium... Or incomplete ( Fig 7 ) Abu Rumeileh, S., & amp Shah... Razem, F. ( selective and differential media lab report conclusion ) of results, lack of color change and growth in PEA medium EMB... For 48 hours N. P. ( 2011 ): differential media 2 Learning Objectives the student will Use techniques! That might have influenced the outcome of results concentration to only allow for the identification of the would! Red indicator and is 7 % made up of Nalco ( Wallace & amp ; Shah N.! The student will Use aseptic techniques in the human gut, and combination selective-differential.... In this experiment will Use aseptic techniques in the experiment been used in this experiment kinds organisms! Darker colonies diarrhea and vomiting example of this experiment and motility agar used... Operon mutants words, they indicate whether or not a certain organism can carry out particular reactions... Agar plates on pH, deterring bacterial growth ( MCK ), are! Organisms or Both, Abu Rumeileh, S., & amp ; Jones, 1996.! Positive bacteria and is 7 % made up of Nalco ( Wallace amp. To culture, Both microscopy and motility agar are used to confirm microbial mobility organism, the! Media include: differential media 2 Learning Objectives the student will Use aseptic techniques in the safe of... While S. Aureus exhibited gamma-hemolysis, the gene is termed a marker valve infection, pneumonia and bone infections species.
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