1. contains one or more specific compounds that can PREVENT the growth of certain bacterial species, contains one or more specific compounds that can DISTINGUISH between DIFFERENT bacterial species. NOT all Gram negative bacteria produce the same AMOUNT of acidic compounds if they can ferment lactose or sucrose, Poor to NO growth = Color changes on the media were observed and used to identify the unknown bacterium. Gram positive bacteria, Growth = Gram negative bacteria 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. 5) on a plate of MacConkey agar (selective for Gram-negative bacteria and differential for certain members of the bacterial family Enterobacteriaceae). B. the growth of a broad variety of bacteria and other nutrients, it is non-selective and hence was Differential media: A differential medium contains additives that cause an observable color change in the medium when a particular chemical reaction occurs. The aim of this experiment is to illustrate the uses of selective Some of these strains P. aeruginosa and E. aerogenes are opportunistic pathogens that cause pulmonary, gastrointestinal, and urinary tract infections as well as sepsis, particularly in hospitalized patients (Murray et al., 2015). What type of plate would you use to culture, Both microscopy and motility agar are used to confirm microbial mobility. The Journal of Horticultural Science and Biotechnology, 19(2), 122-128. BLUISH / GREEN bacterial colonies = RISE in pH of media = NO fermentation of sugars but breakdown of proteins = alkaline products made Selective media contain substances that will inhibit growth of organisms while allowing for only a specific type of organism to grow. These will be your pure cultures for Lab 5 (Direct and Indirect stains). * Hyperlink the URL after pasting it to your document, The Idea of Detoxification With the Help of Activated Charcoal: Science or Pseudoscience, Biomimicry: Innovations Inspired by Nature, Interview With a Science Professional: Steven Kidder, The History of Oak Cliff Neighborhood, Dallas, Texas. Bromthymol blue dye (differential) As one of the media used to identify the unknown bacterium, EMB is a differential and selective medium. Table 1. bacteria and encourages the growth of gram positive bacteria. For each medium, pour into its specific culture medium one for each delbrueckii subsp. For example, organisms that Tabulated Results that Identified the Unknown Bacterium. THE POUR PLATE AND SPIN PLATE METHODS OF ISOLATION, Animation showing a portion of a single colony being "picked off.". Streptococcuseosin methylene blue (EMB), which is differential for lactose and sucrose fermentation. Journal of Clinical Gram-positive organisms are resistant to phenylethy alcohol because they have a protective thick cell wall. The yellow region is due to the fermentation of It also shows how the 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. 3. Accessibility StatementFor more information contact us atinfo@libretexts.orgor check out our status page at https://status.libretexts.org. One plate of each of the following media: Trypticase Soy agar, Columbia CNA agar, and MacConkey agar. Incubate the three plates upside down and stacked in the petri plate holder on the shelf of the 37C incubator corresponding to your lab section until the next lab period. International journal of This culture medium can also be used to distinguish microorganisms that metabolize lactose from those that cannot utilize this sugar through a color indicator (Antony, Paul, & Silvester, & Abdulla, 2016). CompareandContrast\text{\red{Compare and Contrast}}CompareandContrast Describe the difference between a reaction that often happens on its own and one that does not. Preparation of Medium: In addition, molecular It is an enriched medium with sheep blood, tryptones, and soybeans to allow bacteria to obtain nutrients from proteins. 4. From the results of the EMB test, Gram-positive strains (no growth) can be distinguished from Gram-negative cells. Test #1: Lab Experiment. well as Aureus. These are used only for enteric bacteria which are found in the. Pick off isolated colonies of microorganisms growing on a streak plate and aseptically transfer them to sterile media to obtain pure cultures. In the Eosin Methylene Blue Agar plate, E. coli appears large. A blood sample was then enriched medium used in this experiment. Combination selective and differential media: A combination selective and differential medium permits the growth of one group of organisms while inhibiting the WebCultivation Media for Bacteria. Also E. coli would grow on contaminated water or stale food. Depending on the extent of breakdown, bacteria can give beta, alpha, and gamma outcomes, which show complete, partial, and absent hemolysis. When picking off single colonies, remove the top portion of the colony without touching the agar surface itself to avoid picking up any inhibited bacteria from the surface of the agar. Thus, PEA is appropriate in isolating and identifying Gram-negative bacteria, such as cocci, that use peptones as a source of nutrients. "Bacteria Lab: Enriched, Selective, Differential Media." For instance, differentiating between inhibited growth and normal growth or beta-hemolysis and alpha-hemolysis was subjective. The tube is placed on ice for a few minutes and if the media fails to solidify it is considered a positive test. The exact streak plate method that one uses to generate isolated colonies is not too critical. medium in a conical flask under sterile aseptic conditions. MacConkey (MCK), which is differential for lactose fermentationmannitol salt agar (MSA), which is differential for mannitol fermentation. observation and record the results. various bacterial strains and microorganisms respond to growth in mediums with varying DARK PURPLE to BLACK bacterial colonies GREEN METALLIC SHEEN = DROP in media pH = LARGE amounts of acidic products made = VIGOROUS fermentation of lactose and/or sucrose, 1. The following lab you will prepare microscopy slides of each of the two pure cultures to determine if they are indeed pure. StudyCorgi. Poor/No growth = Inhibited by Bile Salts = Gram Positive samples of Staphylococcus aureus and Escherichia Coli. Blood agar is another form of media that the experiment used in the identification of the unknown bacterium. distinguishes between related Media formulation may combine ingredients of (1315) Therefore, boronic acid networks often exhibit self-healing properties, (1618) are injectable, (19,20) and have stimuli-responsive behavior. Research the oxidase test and describe how it is performed. This paper was written and submitted to our database by a student to assist your with your own studies. Thus, in this experiment, lactose-users like E. faecalis, and E. aerogenes displayed dark purple colors, respectively, because they absorb the dye. b) Overload the addition, subtraction, multiplication and division operators for this class. Orange/Yellow Growth = drop on pH = Large acidic = products made = fermentation of sugars = Not Salmonella or Shigella Mannitol Salt Agar and its expected there would be a change in the medium color due to the There are many types of media used in the studies of microbes. COLORLESS bacterial colonies = NO change in media pH = NO acidic products present = NO fermentation of lactose OR sucrose Since EMB medium inhibits the growth of Gram-positive bacteria, it provided the basis for the identification of the unknown bacteria. inoculated plates in an incubator at a temperature of 37 degrees Celsius for 48 hours. 4 and Fig. Given a mixture of a Gram-positive and a Gram-negative bacterium and plates of Columbia CNA, MacConkey, and Trypticase Soy agar, describe the steps you would take to eventually obtain pure cultures of each organism. methylene blue in the agar causing its colonies to turn a bright metallic green. c) Overload the relational and equality operators for this class. Shen, C., & Zhang, Y. The sterilize again and inoculate E. coli in Eosin "Bacteria Lab: Enriched, Selective, Differential Media." (1987). Follow oral and written instructions and manage time in the lab efficiently. In Lab 4 we will use this technique as part of the plate count method of enumerating bacteria. POSSIBLY SALMONELLA OR SHIGELLA, Growth = Gram negative bacteria Many such media will be used in future labs to aid in the identification of microorganisms. StudyCorgi. However, there are some strains that harmful that causes diarrhea id one drinks Enriched media are supplemented with nutrient sources and growth factors for culturing fastidious cells (Basu et al., 2015). depending on original sample density. Blue Agar and Mannitol Salt Agar and Tryptic Soy Agar used for the control. 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. 3). 4. Mannitol Salt Agar (MSA): Mannitol salt agar is both a selective and differential media used for the isolation of pathogenic Eosin Methylene Blue Agar being a selective medium favors the growth of gram negative In such cases, the gene is termed a marker. X-gal plates, which are differential for lac operon mutants. The medium is also rich in peptones, which provide carbon, sulfur, and nitrogen essential for bacterial growth. Terrific Broth (TB) is used with glycerol in cultivating recombinant strains of Escherichia coli. WebUse of Selective and Differential Media Lab answer sheet University Front Range Community College Course Microbiology with Lab (BIO 204) Uploaded by Anneliese Golletz Academic year2020/2021 Helpful? It lacks inhibitory substances. Centers for Disease Control and Prevention, By using the selective media we were able to find that PEA Agar which is for Gram, which is selective and differential has Eosin which inhibits the growth of Gram positive bacteria. A selective medium is a medium that contains antimicrobials, dyes or alcohol that supports the growth of certain organisms, while inhibiting the growth of NOT all Gram negative bacteria can ferment sucrose to produce acidic compounds 1. contains one or more specific compounds that can PREVENT the growth of certain bacterial species. (2021, June 26). Salmonella & Shigella CANNOT breakdown lactose, sucrose or salicin sugars However there was no indole used and some of the agars, were not used in our observations. 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