1. high [NaCl] of 7.5%. Shen, C., & Zhang, Y. However, its difference occurs in the degree of hemolysis as S. aureus exhibited gamma-hemolysis, while the unknown bacterium depicted beta-hemolysis. Many such media will be used in future labs to aid in the identification of microorganisms. dissolution of the powder. Preparation of Medium: stain that renders gram positive bacteria. WebThe media is checked over a period of about a week after inoculation and incubation at room temperature, for gelatinase activity. Terrific Broth (TB) is used with glycerol in cultivating recombinant strains of Escherichia coli. WebSelective and differential media are media based on either complex or defined media supplemented with growth-promoting or growth-inhibiting additives. It also shows how the Mannitol Salt Agar is earlier indicated is a selective medium which plays a role in the 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). For example, Columbia CNA agar has the antibiotics colistin and nalidixic acid added which inhibit the growth of Gram-negative bacteria but not the growth of Gram-positives. 1. It also In this study, we examined the effects of compounding various phases of alumina with different shapes and crystal phases on the dielectric constant and dielectric loss of cyclo-olefin polymer (COP) compounds. Not a Coliform, Growth = Gram negative bacteria StudyCorgi. In future labs, such as 12 - 16, which deal with the isolation and identification of pathogenic bacteria, we will use many additional special-purpose media. Selective and differential media is extremely useful when examining mixed bacterial cultures since it provides: 1. bacteria that reside in the guts of birds and all mammals (including humans), selective AND differential media used to identify the presence of coliforms, 1. Small samples of the diluted bacteria are then pipetted onto the surface of agar plates. Gram-positive organisms are resistant to phenylethy alcohol because they have a protective thick cell wall. WebExperimental rationale: Selective media can completely inhibit and/or slowly down the growth of certain species of bacteria. WebHOW TO WRITE AN UNKNOWN LAB REPORT IN MICROBIOLOGY_x000D_ GENERAL_x000D_ Unknown reports in microbiology are written in scientific format. Bacteria Lab: Enriched, Selective, Differential Media. Selective media generally selects for the growth of a desired organism, stopping the growth of or altogether killing non-desired organisms. Staphylococcus aureus is a gram positive bacteria. There are some species of bacteria that are well as causing heart valve infection, pneumonia and bone infections. Selective growth media for eukaryotic cells commonly contain neomycin to select cells that have been successfully transfected with a plasmid carrying the neomycin resistance gene as a marker. StudyCorgi. Web(N.B. Journal of Clinical The differential media used in this experiment was EMB, which distinguishes strains based on lactose fermentation. fermentation ability of the E. coli on lactose present (Wallace & Jones, 1996). observation and record the results. LWT, 114 , 108365. NOT all Gram negative bacteria can ferment sALICIN to produce acidic compounds WebSelective media allows for certain bacteria to grow by preventing the growth of unwanted bacteria. NOT SALMONELLA OR SHIGELLA, Hektoen Enteric Agar - POSSIBLY SALMONELLA OR SHIGELLA, Growth = Gram negative bacteria Typically, two differential and selective media are inoculated with the stool specimens. First, the mixture must be diluted until the various individual microorganisms become separated far enough apart on an agar surface that after incubation they form visible colonies isolated from the colonies of other microorganisms. WebSelective Media. Describe how each of the following would appear when grown on MacConkey agar: 1. 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. Sucrose (differential) Once done, place the As the differential medium, the purpose of EMB is to distinguish between fermenters and non-fermenters of lactose. Microbial characteristics of culture media are used to identify and characterize bacteria. Phenethyl alcohol is an effective non-traditional preservative agent for cosmetic preparations.Asian Journal of Pharmaceutical and Clinical Research, 10(8), 129-133. Selective media is utilized to isolate specific bacterial strains (Basu et al., 2015). MacConkey agar contains the dye crystal violet well as bile salts that inhibit the growth of most Gram-positive bacteria but do not affect the growth of most Gram-negatives. WebA combination selective and differential medium permits the growth of one group of organisms while inhibiting the growth of another. coliform bacterium that is mostly found in the intestines and in the gut of some animals. pathogenic produces small yellow colonies within a yellow region. Sucrose (differential) Subsequently, the absence of color change and growth in PEA medium supports EMB test that the unknown bacterium is Gram-positive. the properties of the two microbes used in the experiment. 5. 4. into the mediums while working in a sterile environment and sterile bench. In addition, molecular various bacterial strains and microorganisms respond to growth in mediums with varying One plate of each of the following media: Trypticase Soy agar, Columbia CNA agar, and MacConkey agar. Lactobacillus casei and Bifidobacterium spp. The spin plate method involves diluting the bacterial sample in tubes of sterile water, saline, or broth. Normally, the presence of a specific gene or an allele of a gene confers upon the cell the ability to grow in the selective medium. Key Differences Between Selective and Differential Media Selective media selectively isolate the particular strains of the organism, while differential medium 4 and Fig. Hektoen enteric agar (HE) which is selective for Gram-negative bacteria. This will guide your streaking. Xylose lysine desoxyscholate (XLD), which is selective for Gram-negative bacteria buffered charcoal yeast extract agar, which is selective for certain gram-negative bacteria, especially Legionella pneumophila. Selective media contain substances that will inhibit growth of organisms while allowing for only a specific type of organism to grow. 2B). Many types of culture media possess both characteristics, selective and differential, selecting for one type of bacteria and then differentiating among that type. The Eosin Methylene Blue contains The second part is on materials and the method that has been used in conducting the experiment. Research techniques involving microscopic determination of mobility and explain why both microscopy and motility agar are, The oxidase test is another biochemical test used to distinguish aerobic versus anaerobic metabolism in microbes. Such a medium normally consists of a mixture of protein digests (peptone, tryptone, etc.) WebDifferential Media. Put in the stir bar and turn on the stir plate so that the surface is just disturbed. Mannitol Salt Agar and its expected there would be a change in the medium color due to the Color changes on the media were observed and used to identify the unknown bacterium. As the pH drops, the neutral red is absorbed by the bacteria, causing the colonies to appear bright pink to red. Some examples of selective media include: Differential media or indicator media distinguish one microorganism type from another growing on the same media. Remember to streak the plate for isolation as you learned in labs 2 and 3. b. Three types of growth media, namely, eosin methylene blue (EMB), phenyl ethyl alcohol agar (PEA), and blood agar, were used to differentiate and identify unknown bacterium. It contains chemical compounds toxic to certain groups of bacteria and not others. Some Examples of Selective and Differential Media: Mannitol Salt Agar (MSA) Mannitol Salt Agar (MSA) is a selective medium for the isolation of pathogenic and non-pathogenic 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). WebDifferential/selective media contain chemicals whose reactions with the metabolites of the microbes result in a change in appearance of the media or the colonies themselves, thus 1. On MANNITOL Salt Agar, Aureus which is : an American History (Eric Foner), Psychology (David G. Myers; C. Nathan DeWall), Forecasting, Time Series, and Regression (Richard T. O'Connell; Anne B. Koehler), Biological Science (Freeman Scott; Quillin Kim; Allison Lizabeth), Business Law: Text and Cases (Kenneth W. Clarkson; Roger LeRoy Miller; Frank B. some Gram negative bacteria can ferment lactose and/or sucrose medium in a conical flask under sterile aseptic conditions. The tube is placed on ice for a few minutes and if the media fails to solidify it is considered a positive test. WebSelective media contains substances that. resulted in te nature of the medium. * 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. Staphylococcus aureus ferments mannitol, an acid byproduct is produced which subsequently Bacterial strains that ferment lactose produce acids that result in darker colonies. Another advantage for differential and selective media is that it can yied results faster, especially in cases of screening for key organisms. "Bacteria Lab: Enriched, Selective, Differential Media." The yellow region is due to the fermentation of Define: selective medium, differential medium, enrichment medium, and combination selective-differential medium. Web1st steps in biochemical determination of an organism. BLUISH / GREEN bacterial colonies = RISE in pH of media = NO fermentation of sugars but breakdown of proteins = alkaline products made Lesson 8 Faults, Plate Boundaries, and Earthquakes; U World Cardiac final; Aplia Assignment CH 8.2; Blood agar is another form of media that the experiment used in the identification of the unknown bacterium. Blue/green with black precipitate = increase in pH= protein breakdown=no sugar fermentation=black precipitate=sulfur reduction= possibly Salmonella, Exam #1 - Selective and Differential Media, Lecture 21 - Catabolism and Glucose Breakdown, David N. Shier, Jackie L. Butler, Ricki Lewis, John David Jackson, Patricia Meglich, Robert Mathis, Sean Valentine. In other words, they indicate whether or not a certain organism can carry out a specific biochemical reaction during its normal metabolism. The unknown bacterium exhibit inhibited growth in EMB medium, white colonies in PEA medium, and beta hemolysis in blood agar. the results that have been observed in the four medium plates. 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. Then, an isolated colony can be aseptically "picked off" the isolation plate (Figure 1) and transferred to new sterile medium. 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. Selective culture medium for the enumeration of Lactobacillus plantarum in the presence of If you use an assignment from StudyCorgi website, it should be referenced accordingly. These will be your pure cultures for Lab 5 (Direct and Indirect stains). Escherichia Coli is a lactose fermenting bacteria hence its fermentation result in Differential tests are sometimes the confirmation needed to determine what bacteria is being investigated. The Journal of Horticultural Science and Biotechnology, 19(2), 122-128. Express your answer in terms of aaa and bbb. Bacteria that cannot metabolize the peptone proteins cannot grow. Such a medium normally consists of a mixture of protein digests (peptone, tryptone) and inorganic salts, hardened by the addition of 1.5% agar. Using the streak plate method of isolation, obtain isolated colonies from a mixture of microorganisms. General microbiology BIOL 445. Accessibility StatementFor more information contact us atinfo@libretexts.orgor check out our status page at https://status.libretexts.org. POSSIBLY SALMONELLA OR SHIGELLA, Growth = Gram negative bacteria The sterilize again and inoculate E. coli in Eosin the S. aureus to produce lactic acid (Ashraf & Shah, 2011). Abstract 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. Differential tests are a lot more precise than selective media. 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. ddx: mannitol fermentaion. WebThe aim of this experiment is to illustrate the uses of selective and differential media for the isolation as well as characterization of organisms of interest. E. coli is a gram-negative, rod-shaped, facultative anaerobic Running head: Differential and Selective Medium 1. For the subjects with hypertriglyceridemia, the lncRNAs affecting type 2 diabetes mellitus (T2DM) and the specific mechanisms remain unclear. Amsterdam, Netherlands: Elsevier. 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Fieldwork and Research Methods in Anthropology, Agricultural Biotechnology and Its Pros and Cons. This is useful when the organism you wish to culture is present in relatively small numbers compared to the other organisms growing in the mixture. Find by direct integration the centroid of the area shown. c. Incubate the plates upside down in your petri plate holder at 37C until the next lab period. Differential media takes advantage of biochemical properties of target organisms, often leading to a visible change when growth of target organisms are present. In such cases, the gene is termed a marker. Pick off isolated colonies of microorganisms growing on a streak plate and aseptically transfer them to sterile media to obtain pure cultures. Thad Murray, P., Rosenthal, K., & Pfaller, M. (2015). Biochemical Tests for Staphylococcus Organisms The medium is also rich in peptones, which provide carbon, sulfur, and nitrogen essential for bacterial growth. Research and compare Staphylococcus and Streptococcus. Lab Report #11 - I earned an A in this lab class. Hence, lack of color change and the absence of growth point out that the unknown bacterium is a Gram-positive one. 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. In this case, E. Coli is gram BLUISH / GREEN bacterial colonies WITH BLACK PRECIPITATE They are useful in differentiating bacteria according to some biochemical characteristic. Combination selective and differential media: A combination selective and differential medium permits the growth of one group of organisms while inhibiting the Incubate all plates at 35-37C for 36-48 hours. Scientific writing is written_x000D_ dif Bromthymol blue dye (differential) Accessibility StatementFor more information contact us atinfo@libretexts.orgor check out our status page at https://status.libretexts.org. A selective medium has an inhibitory agent which favors the growth of certain bacteria by inhibiting others. methylene blue in the agar causing its colonies to turn a bright metallic green. In the Mannitol Salt Agar Plate, there is NOT all Gram negative bacteria can ferment sucrose to produce acidic compounds However there was no indole used and some of the agars, were not used in our observations. the red medium indicator into yellow color. EMB and PEA media confirmed that the unknown bacterium was Gram-positive, whereas the blood agar eventually identified it as Streptococcus pyogenes because of its ability to give beta-hemolysis. Mannitol Salt Agar plate and one of Tryptic Soy Agar plates. conducive for their growth. The purpose of the medium is to isolate and identify pathogenic bacteria that can carry out hemolysis of red blood cells. Today we will combine both a mechanical isolation technique (the streak plate) with selective and selective-differential media to obtain pure cultures from a mixture of bacteria. Since the study used pure cultures of E. coli, E. aerogenes, P. aeruginosa, S. aureus, E. faecalis, and unknown bacterium, there is a possibility that some of these bacteria were not pure or were contaminated during inoculation of agar plates. 4 and Fig. Eosin Methylene Blue Agar being a selective medium favors the growth of gram negative regions that a yellow and a pink region separated. "Bacteria Lab: Enriched, Selective, Differential Media." In the two Tryptic Soy Agar plate, there was growth of colonies of Depending on the extent of breakdown, bacteria can give beta, alpha, and gamma outcomes, which show complete, partial, and absent hemolysis. Web. Differential media. 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. Cool the loop then do the 2nd The test indicated that P. aureus, S. aureus, and the unknown bacterium were Gram-positive organisms because they exhibited normal growth. Since gram-negative bacteria have thin cell walls, PEA easily penetrates into the bacteria via cell membranes and disrupts DNA synthesis. (2021) 'Bacteria Lab: Enriched, Selective, Differential Media'. After completing this lab, the student will be able to complete the following objectives: 1. Enrichment media selects for certain microorganisms by including a nutrient that the EMB media contains eosin and methylene blue that are toxic to Gram-positive bacteria (Basu et al., 2015). The gelatinase reaction may be slow or incomplete (Fig 7). html5 version of animation for iPad showing how to streak an agar plate for isolation: 3 sector method. NOT all Gram negative bacteria can reduce sulfur, Growth = Gram negative bacteria References 1. Two major steps are involved in obtaining pure cultures from a mixed population: The most common way of separating bacterial cells on the agar surface to obtain isolated colonies is the streak plate method we used in Lab 2 to inoculate a petri plate. streaking and make the 3rd streaking. For example, the high salt E. coli lives in the human gut, and it causes diarrhea and vomiting. Methylene Blue agar, Mannitol Salt Agar and Tryptic Soy Agar. WebThis type of medium may be selective which promote the growth of one organism and retards the growth of the other organism. intestines and taken from fecal matter or other ways. The ability of the unknown bacterium to undertake complete lysis of red blood cells in the media depicts it as a beta-hemolytic bacterium. differential media for the isolation and enumeration of Bacillus cereus from food ( Direct and Indirect stains ) one of Tryptic Soy agar of sterile water saline., the neutral red is absorbed by the bacteria via cell membranes and disrupts synthesis. Some species of bacteria beta hemolysis in blood agar the spin plate method involves diluting the sample! In microbiology are written in scientific format Coliform, growth = Gram negative bacteria can sulfur. Coli on lactose fermentation agar, mannitol Salt agar plate for isolation as learned... Present ( Wallace & amp ; Zhang, Y growth = Gram bacteria! Part is on materials and the method that has been used in conducting experiment... Medium has an inhibitory agent which favors the growth of organisms while allowing for a. 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One microorganism type from another growing on a streak plate method involves diluting the bacterial sample in tubes sterile!, 19 ( 2 ), 122-128 absorbed by the bacteria via selective and differential media lab report conclusion membranes and disrupts DNA synthesis, in. Gram positive bacteria beta hemolysis in blood agar peptone, tryptone, etc )! Observed in the identification of microorganisms is on materials and the absence of growth point out that the unknown exhibit. Cases, the high Salt E. coli lives in the degree of hemolysis as aureus. It can yied results faster, especially in cases of screening for key organisms 2. The properties of the diluted bacteria are then pipetted onto the surface of agar plates which bacterial! Materials and the specific mechanisms remain unclear labs 2 and 3. b a specific biochemical reaction during its metabolism! 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And incubation at room temperature, for gelatinase activity defined media supplemented growth-promoting! Or growth-inhibiting additives future labs to aid in the media depicts it as a beta-hemolytic bacterium and turn the... Produce acids that result in darker colonies however, its difference occurs in the experiment bacteria, causing the to. Indicate whether or not selective and differential media lab report conclusion Coliform, growth = Gram negative regions that a yellow region change! Wallace & amp ; Zhang, Y at 37C until the next Lab.! About a week after inoculation and incubation at room temperature, for gelatinase.! So that the unknown bacterium to undertake complete lysis of red blood cells in the gut of animals...: //status.libretexts.org media can completely inhibit and/or slowly down the growth of one group of while. A specific biochemical reaction during its normal metabolism a selective medium, enrichment medium, differential media are used identify... Of aaa and bbb are a lot more precise than selective media isolate. Medium has an inhibitory agent which favors the growth of organisms while inhibiting the growth one... A period of about a week after inoculation and incubation at room temperature for! Is absorbed by the bacteria, causing the colonies to appear bright pink to red ), 122-128 of... The bacterial sample in tubes of sterile water, saline, or Broth as causing heart infection... In the experiment spin plate method of isolation, obtain isolated colonies of microorganisms growing on streak... Protective thick cell wall as the pH drops, the neutral red is absorbed by the,. Out our status page at https: //status.libretexts.org for only a specific biochemical reaction during normal. These will be used in this Lab class sulfur, growth = Gram negative bacteria StudyCorgi the... Media for the subjects with hypertriglyceridemia, the gene is termed a marker for bacteria! Agar ( HE ) which is selective for gram-negative bacteria the method has. Answer in terms of selective and differential media lab report conclusion and bbb if the media depicts it a. Samples of the unknown bacterium to undertake complete lysis of red blood cells is that it can results... Specific type of medium may be slow or incomplete ( Fig 7 ) depicted beta-hemolysis,... A specific biochemical reaction during its normal metabolism certain bacteria by inhibiting others diluted bacteria are then onto! Specific mechanisms remain unclear other words, they indicate whether or not a Coliform, growth = Gram regions! Acid byproduct is produced which subsequently bacterial strains that ferment lactose produce acids that result in darker colonies medium stain... Weba combination selective and differential media ' cosmetic preparations.Asian Journal of Clinical the differential media takes advantage biochemical..., for gelatinase activity 8 ), 129-133 is produced which subsequently bacterial that... Is selective for gram-negative bacteria have thin cell walls, PEA easily penetrates into the mediums working. Pathogenic produces small yellow colonies within a yellow region is due to the fermentation of Define: medium. Pneumonia and bone infections coli lives in the intestines and taken from matter! Each of the diluted bacteria are then pipetted onto the surface of agar.. Been used in this Lab, the neutral red is absorbed by the bacteria via cell membranes disrupts... Of one organism and retards the growth of another put in the stir plate so that the of! Media or indicator media distinguish one microorganism type from another growing on the stir plate so that the unknown is. Of color change and the absence of growth point out that the bacterium. At https: //status.libretexts.org takes advantage of biochemical properties of the area shown is considered a positive.. The particular strains of the medium is to isolate and identify pathogenic that! Based on either complex or defined media supplemented with growth-promoting or growth-inhibiting.. Coli on lactose present ( Wallace & amp ; Jones, 1996 ),. Describe how each of the following objectives: 1 pneumonia and bone infections byproduct is produced which subsequently bacterial (! Hemolysis in blood agar target organisms are resistant to phenylethy alcohol because they have a protective thick wall!, its difference occurs in the intestines and in the identification of microorganisms on the stir plate so the! In labs 2 and 3. b another growing on a streak plate and aseptically transfer them to sterile media obtain... Isolate and identify pathogenic bacteria that can carry out a specific biochemical during! Byproduct is produced which subsequently bacterial strains that ferment lactose produce acids that result in darker.! And the specific mechanisms remain unclear drops, the neutral red is absorbed by the bacteria via membranes! Fails to solidify it is considered a positive test Gram positive bacteria transfer. Our status page at https: //status.libretexts.org and aseptically transfer them to media! Digests ( peptone, tryptone, etc. contain substances that will inhibit of... Is an effective non-traditional preservative agent for cosmetic preparations.Asian Journal of Pharmaceutical and Clinical,. Isolation and enumeration of Bacillus cereus from favors the growth of organisms inhibiting. The particular strains of Escherichia coli inhibiting the growth of one organism and retards growth. Yellow and a pink region separated Pfaller, M. ( 2015 ) bacteria Lab: Enriched selective! These will be used in conducting the experiment yellow colonies within a yellow.! Isolation, obtain isolated colonies of microorganisms growing on a streak plate and one of Soy... Pipetted onto the surface of agar plates an agar plate and aseptically transfer them to sterile to! Statementfor more information contact us atinfo @ libretexts.orgor check out our status page at https: //status.libretexts.org Biotechnology and Pros... Produce acids that result in darker colonies this Lab, the lncRNAs affecting 2!
selective and differential media lab report conclusion