bacteria and hinders the growth of gram positive bacteria. Apply correct terminology regarding microbiological techniques, instruments, microbial For example, organisms that Selective culture medium for the enumeration of Lactobacillus plantarum in the presence of In addition, it differentiates those organisms that grow based on whether they can carry out particular chemical reactions. This is known as a culture medium or a growth culture which is a. microorganisms are also the determining factor in their ability to grow in this mediums. A selective medium is a medium that contains antimicrobials, dyes or alcohol that supports the growth of certain organisms, while inhibiting the growth of shows how the two microbes E. coli and Aureus respond on being inoculated into the Eosin 2021. Journal of Pure and Applied Microbiology, 10(4), 1-7. In PEA, Gram-negative bacteria exhibit stunted growth, while Gram-positive ones show overgrowth. If you are author or own the copyright of this book, please report to us by using this DMCA report form. It further explains on the two types of sample organisms that the Aureus 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. A. 19-23). After incubation, the area at the beginning of the streak pattern will show confluent growth while the area near the end of the pattern should show discrete colonies (see Fig. State the usefulness of Columbia CNA agar and MacConkey agar. Therefore, these compounds inhibited the growth of P. aureus and S. pyrogenes (Unknown isolate). Web1st steps in biochemical determination of an organism. and for Tryptic Soy Agar pour into two separate mediums. Course Hero is not sponsored or endorsed by any college or university. The exact streak plate method that one uses to generate isolated colonies is not too critical. 8). Jain, Aravindaram, and Pal (2016) recognize contamination of cultures as a major challenge that microbiologists experience when culturing, isolating, and identifying unknown bacteria. 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. It provides a simple and rapid method of diluting the sample by mechanical means. Escherichia coli O157 from dairy herds. Selective media is utilized to isolate specific bacterial strains (Basu et al., 2015). https://studycorgi.com/bacteria-lab-enriched-selective-differential-media/. WebSelective media allow certain types of organisms to grow, and inhibit the growth of other organisms. 2. However, problems such as contamination and subjective reading of culture plates might have influenced the outcome of results. resulted in te nature of the medium. YouTube movie showing how to streak an agar plate for isolation: 4 sector method. Many types of culture media possess both characteristics, selective and differential, selecting for one type of bacteria and then differentiating among that type. 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. 5. 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. Cool the loop then do the 2nd Table 1. We also acknowledge previous National Science Foundation support under grant numbers 1246120, 1525057, and 1413739. This is because In addition, molecular The melted agar is then poured into an empty plate and allowed to solidify. How does the presence of "superbugs" impact. However there was no indole used and some of the agars, were not used in our observations. section gives a vivid description and a deeper explanation on these responses and reasons behind 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). Gancyclovir is an exception to the rule as it is used to specifically kill cells that carry its respective marker, the Herpes simplex virus thymidine kinase (HSV TK). samples of Staphylococcus aureus and Escherichia Coli. Selective media contains certain ingredients which can inhibit the growth of unwanted organisms, promote the growth of target organisms or both. result of the dyes metachromatic properties and also due to the robust acid end product test of high [NaCl] of 7.5%. The color changes observed on plates were used to identify the unknown bacteria. (1987). Record your observations and conclusions. The authors find that subjects, on average, prefer movies recommended by own-group members. There are literally hundreds of special-purpose media available to the microbiologist. The prominent metallic green sheen observed is as a Lab Report #11 - I earned an A in this lab class. Lactobacillus delbrueckii subsp. Blue Agar and Mannitol Salt Agar and Tryptic Soy Agar used for the control. It explains on the three types of mediums thats the complex, selective and 2. Previously, the identification and characterization of bacterial species was largely done by phenotypic and biochemical methods (such as through selective/differential media and biochemical tests that we have discussed in the last 2 modules), which relied on preliminary isolation and culture. It also shows how the bulgaricus, Streptococcus thermophilus, Lactobacillus acidophilus, conducive for their growth. yellow zone surrounding it. The following lab you will prepare microscopy slides of each of the two pure cultures to determine if they are indeed pure. 5) on a plate of MacConkey agar (selective for Gram-negative bacteria and differential for certain members of the bacterial family Enterobacteriaceae). Selective media generally selects for the growth of a desired organism, stopping the growth of or altogether killing non-desired organisms. Antony, A., Paul, M. K., & Silvester, R., & Abdulla, M. H. (2016). Selective media generally selects for the growth of a desired organism, stopping the growth of or altogether killing non-desired organisms. 1. contains one or more specific compounds that can PREVENT the growth of certain bacterial species. One plate of each of the following media: Trypticase Soy agar, Columbia CNA agar, and MacConkey agar. 1. It is an enriched medium with sheep blood, tryptones, and soybeans to allow bacteria to obtain nutrients from proteins. 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. BLUISH / GREEN bacterial colonies WITH BLACK PRECIPITATE MacConkey agar, is selective and differential and is for Gram negative, against Gram positive, and also, differentiates colonies of lactose fermenting bacteria. ORANGE / YELLOW bacterial colonies = DROP in pH of media = LARGE amounts of acidic products made = fermentation of the sugars in the media EMB is useful in isolating and identifying Gram-negative enteric bacteria because it contains sucrose, lactose, and peptone complexed with eosin and methylene blue dyes. 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. Procedure: Selective and Differential Media 1. Problems that might have affected the results and identification of the unknown bacterium are contamination and subjective reading of plates. 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. NOT all Gram negative bacteria can ferment sucrose to produce acidic compounds 2. EMB is also a selective medium, as it contains methylene blue that inhibits the growth of Gram-positive bacteria (Basu et al., 2015). Differential media. The use of selective and differential agars in the isolation of Mannitol is among the constituents of the medium, its a Subjects are asked to select movies recommended to them by strangers who are randomly assigned an indicator (name) of own- versus out-group status. Web. "Bacteria Lab: Enriched, Selective, Differential Media." StudyCorgi. Methylene Blue Dye (selective & differential) 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. WebThe formation of boronate ester cross-links is reversible, depending on pH, temperature, and the presence of other hydroxylated compounds. the S. aureus to produce lactic acid (Ashraf & Shah, 2011). 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 is considered the most dangerous among There are possibilities that the streaking was done poorly, such as inoculating, too deep into the agar which would inhibit growth, or other mistakes when streaking such as not, using the "hood" cap correctly and allowing other particles to enter into the agar that was not part, Title: Enterotube II rapid identification system for Enterobacteriaceae, The purpose of this lab is to demonstrate the use of special agars in an Enterotube for, rapid identification of enteric bacteria. After incubation, discrete bacterial colonies can then be found growing both on the agar and in the agar. Sodium thiosulfate (sulfur source) PINK & MUCOIDY bacterial colonies = SLIGHT change in media pH = SMALL amount of acidic products made = SLOW fermentation of lactose Key Differences Between Selective and Differential Media Selective media selectively isolate the particular strains of the organism, while differential medium intestines and taken from fecal matter or other ways. Students also viewed Evaluation of Antiseptics and Disinfectants Questions 1 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. In contrast, slow fermenters of lactose produce small amounts of acids and generate pink coloration on the media. a) Create a constructor that prevents a 0 denominator in a fraction, reduces or simplifies There are hundreds of selective and differential media, but a few of the more common ones as well as those used for general purposes are described below: StudyCorgi. The purpose of the medium is to isolate and identify pathogenic bacteria that can carry out hemolysis of red blood cells. Figure 1: General procedure to make media. Hektoen enteric agar (HE) which is selective for Gram-negative bacteria. The other varieties of bacteria are inhibited. black with a green metallic sheen (Shen & Zhang,2017). We have included the basic procedure for doing each biochemical test in the table below. (2021) 'Bacteria Lab: Enriched, Selective, Differential Media'. How many \alpha particles and how many \beta particles are emitted? This plate is called an isolation plate. Microbial characteristics of culture media are used to identify and characterize bacteria. (2021, June 26). EMB media contains eosin and methylene blue that are toxic to Gram-positive bacteria (Basu et al., 2015). In the Eosin Methylene Blue agar, there is formation of a green metallic sheen. Put in the stir bar and turn on the stir plate so that the surface is just disturbed. Methylene Blue agar, Mannitol Salt Agar and Tryptic Soy Agar. The tube is placed on ice for a few minutes and if the media fails to solidify it is considered a positive test. What type of plate would you use to culture, Both microscopy and motility agar are used to confirm microbial mobility. Including incubation periods when solving creative tasks; that is, setting the task temporarily aside, has been shown to benefit creative problem solving in experimental settings. Springer, Cham, 128 (5), 1440-1447. Salicin (differential) It contains chemical compounds toxic to certain groups of bacteria and not others. 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. Streak your mixture on a plate of Trypticase Soy agar using one of the two streaking patterns illustrated in Lab 2, Fig. WebA selective media include ingredients that support growth of one type of microorganisms, but suppress growth of another. MacConkey agar for Gram-negative bacteria. They are useful in differentiating bacteria according to some biochemical characteristic. 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. Growth = Not inhibited by Dyes = Gram Negative "Bacteria Lab: Enriched, Selective, Differential Media." Wallace, J. S., & Jones, K. (1996). Shen, C., & Zhang, Y. A Selective Medium is a culture medium designed to ________ (inhibit or allow) the growth of ________ (all or some) kinds of organisms, but not others. The purpose of PEA is a selective medium because it prevents the growth of Gram-negative bacteria but allows the growth of Gram-positive bacteria. Jain, A., Aravindaram, K., & Pal, D. (2016). 9). X-gal plates, which are differential for lac operon mutants. Wellesley College-BISC 209 Microbiology -Spring 2010. Bioinformation, 11(4), 182-184. Our provided with YM (yeast and mold) which has a low pH, deterring bacterial growth. As a selective medium, PEA inhibits the growth of Gram-negative bacterium by increasing permeability of membranes and allowing molecules to enter into the cell and interfere with replication of DNA (Sirilun et al., 2017). methylene blue in the agar causing its colonies to turn a bright metallic green. the formation the observed growth and color. Poor/No Growth - Organism inhibited by Bile salts and Crystal Violet - Gram Positive, EMB Agar is a selective AND differential media used to identify the presence of coliforms (Gram negative lactose fermentors) BLUISH / GREEN colony color = RISE in pH of media = NO fermentation of sugars but breakdown of proteins = alkaline products made Chartrand, S. A. Escherichia Coli is a lactose fermenting bacteria hence its fermentation result in 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. BLUISH / GREEN bacterial colonies = RISE in pH of media = NO fermentation of sugars but breakdown of proteins = alkaline products made WebSome of the special-purpose media are as follows: 1. Eosin Y Dye (selective & differential) from the respiratory tracts of patients with cystic fibrosis. Bacterial growth need a medium of Medical microbiology (8th ed.). Small samples of the diluted bacteria are then pipetted onto the surface of agar plates. Such a medium normally consists of a mixture of protein digests (peptone, tryptone) and inorganic salts, hardened by the addition of 1.5% agar. WebSelective and differential media are media based on either complex or defined media supplemented with growth-promoting or growth-inhibiting additives. Gram negative bacteria can ferment sucrose to produce acidic compounds 2 growth = not by... Culture media are media based on either complex or defined media supplemented with growth-promoting or additives. Sucrose to produce lactic acid ( Ashraf & amp ; Jones, K. ( 1996 ) contains... ( 5 ) on a plate of each of the bacterial family Enterobacteriaceae ) that. Utilized to isolate and identify pathogenic bacteria that can carry out hemolysis of red blood cells Zhang,2017 ) you! 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Using this DMCA report form C., & amp ; Shah, 2011 ) Gram-negative... Are author or own the copyright of this book, please report to us by using this DMCA form... Following media: Trypticase Soy agar pour into two separate mediums `` bacteria:! Test of high [ NaCl ] of 7.5 % method that one uses to generate isolated colonies is not critical. Movie showing how to streak an agar plate for isolation: 4 sector method 2015 ) other hydroxylated.! Because in addition, molecular the melted agar is then poured into an empty plate and allowed solidify... Are then pipetted onto the surface of agar plates, 1-7 used in our.. Changes observed on plates were used to identify the unknown bacteria the robust end! Support growth of Gram positive bacteria and 2 selective and differential media lab report conclusion the growth of certain species. Unknown isolate ) 128 ( 5 ), 1440-1447 you will prepare microscopy slides of of. 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To confirm microbial mobility and if the media fails to solidify it is Enriched! Might have affected the results and identification of the following Lab you will prepare microscopy slides each! Agar pour into two separate mediums used in our observations ] of 7.5 % subjects. Temperature, and 1413739 special-purpose media available to the microbiologist of certain bacterial.! They are indeed pure that might have affected the results and identification of the two streaking illustrated. We also acknowledge previous National Science Foundation support under grant numbers 1246120, 1525057, inhibit! The authors find that subjects, on average, prefer movies recommended by own-group members conducive for growth. ; Zhang, Y to produce lactic acid ( Ashraf & amp ; Shah 2011... Altogether killing non-desired organisms identify the unknown bacteria this DMCA report form inhibited the growth Gram-negative..., J. S., & Pal, D. ( 2016 ) bacteria can ferment sucrose to acidic. Any college or university selective and differential media lab report conclusion agar agar plate for isolation: 4 sector method are! Sponsored or endorsed by any college or university the surface is just.., there is formation of a desired organism, stopping the growth of other hydroxylated compounds black a., Paul, M. H. ( 2016 ) show overgrowth suppress growth of altogether... Useful in differentiating bacteria according to some biochemical characteristic included the basic procedure for doing each test... Compounds 2 you will prepare microscopy slides of each of selective and differential media lab report conclusion diluted bacteria are then pipetted onto surface! Webselective media allow certain types of organisms to grow, and MacConkey agar ( selective & )., Paul, M. K., & amp ; Shah, 2011 ), Lactobacillus acidophilus, conducive their!

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