Microbiology lab selective and differential media. Bacteria Lab: Enriched, Selective, Differential Media 2022-10-14
Microbiology lab selective and differential media Rating:
Microbiology lab selective and differential media are important tools used to identify and differentiate various microorganisms. Selective media are designed to favor the growth of specific microorganisms while inhibiting the growth of others. Differential media, on the other hand, are used to distinguish between different types of microorganisms based on their physical and biochemical characteristics.
One example of a selective media is EMB (eosin methylene blue) agar, which is used to differentiate between lactose-fermenting and non-lactose fermenting gram-negative bacteria. Lactose-fermenting bacteria, such as Escherichia coli, will produce acid from the lactose in the media, leading to a change in the pH of the media. This acid production will cause the EMB to change color from purple to pink, allowing for the identification of lactose-fermenting bacteria. Non-lactose fermenting bacteria will not produce acid, and the media will remain purple.
Another example of selective media is MacConkey agar, which is used to differentiate between gram-negative bacteria that are capable of fermenting lactose and those that are not. This media contains bile salts and crystal violet, which inhibit the growth of gram-positive bacteria and allow for the selective growth of gram-negative bacteria. Lactose-fermenting bacteria will produce acid and cause the media to turn pink or red, while non-lactose fermenting bacteria will not produce acid and the media will remain clear.
Differential media, such as blood agar, are used to differentiate between microorganisms based on their ability to produce certain enzymes or their ability to utilize certain substrates. Blood agar contains sheep's blood, which allows for the detection of hemolysis, the destruction of red blood cells. Bacteria that produce certain enzymes, such as streptolysin, can cause the destruction of red blood cells and lead to a clear halo around the bacterial colony on the media. The presence or absence of hemolysis can be used to differentiate between different types of bacteria.
In conclusion, selective and differential media are essential tools in microbiology labs for the identification and differentiation of microorganisms. These media allow scientists to isolate and study specific microorganisms, providing important information about their characteristics and abilities.
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. People that could not would either starve or die of an allergic reaction. There are two factors that I could think of that would cause zero growth on the MSA plate and that would be the use of a non-viable culture or temperature conditions that were unfavorable. Blood agar is a differential medium that distinguishes bacterial species by their ability to break down the red blood cells included in the media. Medical and pathology laboratories often use MacConkey agar to isolate potentially harmful gram-negative bacteria from clinical samples. People that could eat peanuts would be fine. Why or why not? Due to the petri dish having a dilution gradient, growth occurred on part of the plate where cells were not separated and other parts of the plate where there were isolated colonies.
By gathering samples from humans infected with a known type of bacteria, researchers can use differential media to identify the species and biochemical properties of that species, allowing them then to understand the severity of a particular bacterial infection. In addition to the selective bile salts and crystal violet, MacConkey agar contains a pH indicator and the sugar lactose. Bright pink growth with purple agar surrounding growth. Selective Media The next type of media is selective media. Examples of Selective and Differential Media The examples of selective and differential media in this section have previously been mentioned above. Agar Plate Tests Types of Bacteria EMB Indicate Lactose Fermentation by Colony Coloration Phenylethyl Alcohol Blood Agar E.
Lesson Summary Let's review. The quadrant method incubates an agar using a four-streak pattern. Some components in the media serve to inhibit the growth of non-target cells while others enhance the appearance of target colonies. Differential Media Selective vs. Some select by including very specific energy sources or antibiotics in the media. Steps Used in Identifying an Unknown Bacterium in a Laboratory I. Let's take this a little further.
I bet that every one of us knows someone who is allergic to peanuts. In conclusion, the experiment successfully identified the unknown bacterium based on the outcomes of other five bacteria, namely, E. In order to get separate colonies on a streak plate, individual cells are removed from the first colony with an inoculating loop and transferred to the next colony by streaking the bacteria with the loop across each individual colony. In practice specimens are generally inoculated on enriched, differential, and selective media to facilitate rapid identification, diagnosis, and possibly treatment. For instance, differentiating between inhibited growth and normal growth or beta-hemolysis and alpha-hemolysis was subjective.
This is due Mon. Inoculate 4 different bacteria onto each kind of medium. Use discount References Antony, A. For example, if a microorganism is resistant to a certain antibiotic, such as ampicillin or tetracycline, then that antibiotic can be added to the medium in order to prevent other cells, which do not possess the resistance, from growing. A culture can contain only one species of bacteria, called a pure culture, or can contain many different species, called a mixed culture.
Often a medium is formulated so that it is both selective and differential functions. Take a photograph of each culture one photo of each plate showing all growth on that plate. 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. What is a differential medium? A differential media contains specific ingredients or chemicals that allow the observer to visually distinguish which species possess and which species lack a specific biochemical process. It is important to use sterilization technique so the plates will not become contaminated while doing a streak plate 1. Culture media can therefore perform both selective and differential functions this thus reducing cost and labor in real world settings. People that could eat peanuts would be fine.
Microbiology Lab: Selective/Combination Differential Media Flashcards
Now that you know who is allergic to peanuts, suppose you want to encourage the survival of peanut-resistant people while inhibiting the survival of the peanut-allergic. Some members of this genus are harmful pathogens, while others are not. Normally-colored or colorless colonies indicate that the organism ferments neither lactose nor sucrose and is not a fecal coliform. Enriched media are supplemented with nutrient sources and growth factors for culturing fastidious cells Basu et al. As mentioned previously, MacConkey agar also contains bile salts and crystal violet dye to inhibit the growth of gram-positive bacteria thereby allowing gram-negative bacteria to flourish.
The mediums we were given are both selective and differential. Bacteria that cannot metabolize the peptone proteins cannot grow. Take a photograph of each culture one photo of each plate showing all growth on that plate. NFS 2031 Food Microbiology Lab 1 Lab: Biochemical Tests and Selective and Differential Media Objectives Utilize both selective and differential media in growth and identification of bacteria. Microbiologists can therefore use differential and selective media, which contain ingredients that perform the functions of both types of media in one culture, thus reducing the need for two separate processes. In contrast, slow fermenters of lactose produce small amounts of acids and generate pink coloration on the media.
Eosin Methylene Blue Agar EMB is a selective medium which selects for Gram- negative bacteria because of the presence of the dyes eosin and methylene blue which inhibit growth of gram-positive bacteria. Many disease-causing bacteria found in human feces are Gram-negative, like E. The ingredients present in many selective media is determined by the conditions needed for the target organisms to grow. Gram-positive species are unable to grow in the presence of bile salts and crystal violet, ensuring that more colonies will be the Gram-negative pathogens of interest. 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. Blood agar is often used to distinguish between the different species of pathogenic Streptococcus 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.