Mannitol Agar

In the beginning of lab, we were advised to obtain a nutrient agar petri plate, which is used for the cultivation of microbes supporting growth of non-fastidious organisms. Since it contains many nutrients, a wide variety of bacteria and fungi can grow. Taking the plate,

items presently in solid form in the lab kit or purchased separately for this laboratory

In the Voges-Proskauer test, I inoculated the tube with bacteria from my TSA plate and incubated the tube at 37 degrees Celsius for 3 days. After three days I placed some Barrits Reagent A and Barrits Reagent B in the test tube. The color change of red or pink indicates a positive reaction for acetoin which tells you that the organism is a butanediol fermentor.

The purpose of this lab was to identify an unknown microorganism using lab techniques. The importance of identifying microorganisms is essential to the survival of humans, expansion of modern day medicine and improvement of quality of life. In 1884, Hans Christian Gram designed a differential staining technique to identify bacteria that would change the future of microbiology. He give rise to a staining process, known as the Gram stain to differentiate microorganisms into two groups between positive and negative gram staining microorganisms. The Gram stain is essential in a lab technique as it distinguishes the cells based on the physical properties of the individual cell walls, and is almost always the first test preformed to differentiate a microorganism. The identification of weather a microorganism is gram positive or negative can revel the bacteria’s virulence, cell wall structure, resistance to antibiotics, resistance to physical disruptions and so much more. In order to identify the unknown provided, unknown #27, the Gram stain was the first test preformed. After discovering that the unknown bacterium was indefinitely a gram positive microorganism, the vast possibilities were narrowed down. However, In order to more definitively identify the unknown, the next step was to preform biochemical tests. A biochemical test identifies metabolic

Gerhart, D. “Ferdinand, Cohn, a Founder of Modern Microbiology”Features. Nov 1999. Retrieved on January 16, 2014 from microbeworld.org: http://www.microbeworld.org/images/stories/history_pdfs/f3.pdf

During the purification section of this lab, the LB/amp/ara agar plate was examined for well-isolated green colonies and the LB/amp plate was observed for white colonies with space between each other. These colonies were circled on the outside of the plates using a marker. Next, two 15 milliliter culture tubes containing 2 milliliters of nutrient growth media were obtained and labeled “+” and “-“. Using a new inoculation tube, the circled colonies from each plate were scooped out and immersed in their respective culture tubes. Once the bacteria was mixed into the solution, the tubes were sealed and placed horizontally into the 32⁰ incubator for 24 hours.

Just like eukaryote species, not all bacteria species are identical in the way they behave, grow or interact with their environment (Mujtaba & DeJarnette, 2012). Microbes can be unique in the way they grow on nutrient agar (NA) plates. How their colonies form on the agar plates can also be an exclusive property of specific bacteria species. Microbes can grow in the presence of different nutrients, environments and can also be inhibited by or thrive in the presence of specific agents in the medium. For example inoculating a blood agar plate with the organism, can indicate its hemolysis activity, which it will fall in one of the three groups alpha (α), beta (β), or gamma (γ).

You can grow microorganisms in liquid media or on solid media. Most bacteria can be grown in labs as long as the media contain a source of the major nutrients; carbon, nitrogen, sulphur, and phosphorous. They may also need to have other nutrients. These nutrients are made into a broth and the pH and salinity can be adjusted. The nutrient broth is placed in test tubes, which are plugged with cotton wool, capped with foil and then sterilised in an autoclave, at 121c for 20minutes. These tubes are then cooled before they are inoculated. To prepare the streak plates we dipped an inoculating loop into ethanol then placed it in the flame until the loop glowed red. Still holding the inoculating loop by its handle we removed the lid from

While completing the 5 tests I used medium that have a purpose selective and differential. Selective mediums “inhibit the growth of some organisms and encourage the growth of others” (1). Differential mediums differentiate between microorganisms using indicators such as color as the pH of the medium changes (1).

The process of using different media allows seperation of different bacterial organisms for identification relatively quickly. Where come bacteria will grow on blood agar and chocolate agar, some will grow on only one, or on neither. The ph of the media can be changed and the media can be inoculated with various antibiotics known to kill certain strains of bacteria.

The instructor's manual also parallels the laboratory manual, exercise by exercise, providing labels for unlabeled diagrams and answers to questions that appear in the laboratory reports. For some exercises, special instructional suggestions that propose alternative procedures, laboratory equipment, or laboratory techniques are provided.

When isolating the types of bacterium that is gram-positive, motile, halophilic, mannitol fermenters that grow in the presence and absence of oxygen you would use the mannitol salt agar (MSA), mannitol fermentation, and semisolid stab tests. To isolate a halophilic bacterium, mannitol salt agar (MSA) can be used as a test. For a mannitol salt agar (MSA) test, you would need a plate where the agar is mannitol salt and 7.5% NaCl. The 7.5% NaCl mix with mannitol shows the selective and differential part of the test because some bacterium is not able to tolerate the high level, but can be mannitol fermenters.

With the help of his influence and research, Louis Pasteur helped the world understand where germs came from, starting after he graduated from college in 1845 until he died in 1885. Joseph Lister took the research further by adapting the germ research and using disinfectants to improve post surgery recovery. Together they are remembered for their contribution to modern medical science, and so it is appropriate that a process and product are named for

The goal of the streptococcus lab was to isolate and characterize the type of streptococcus microorganism that may be located in the back of the one’s throat (the source of the specimen). In order to isolate a specific type of organism, a sample is collected by doing a throat swap. The sample was streak on a Columbia Nalididxic Acid agar (CNA) plate by using the three way method. The CNA was used as a selective media for colistin and nalidixix acid but also used for differential reactions for hemolytic reaction as well as on a Blood Agar Plate (BAP). On the CNA plate, the antibody Optochin was added to see if there were growth and to check what type of hemolytic reaction it had. If it had alpha hemolytic, then we stop there. If the sample is beta hemolytic, another test is necessary to be done in order to confirm result that was received, which is a test with the Bacitarcian antibiotic. From the BAP, a colony was picked and inoculate in broth for growth in order to

The Indole portion of the test is performed by adding Kovac's reagent to the inoculated SIM medium. The Kovac's reagent reacts with the indole (if indole is present) to produce a pinkish-red or reddish-purple ring around the top of the test tube. If indole isn't present, there will be no color change. The presence of indole indicates that the bacteria produces tryptophanase, an enzyme which breaks down tryptophan into smaller components, one of which being indole.