In Microbiology lab I have learned a variety of different test that can be experimented with bacteria that will help prove what bacteria I have chosen for my project. Therefore, I am writing this paper to show that my results will provide evidence stating that my bacteria is Micrococcus luteus.
More specifically, in finding my evidence, multiple tests were introduced to my bacteria to determine how it would respond. The first test that will be discussed is a gram stain. This is one of the most important parts in figuring out bacteria. Usually a Gram-positive cell will appear purple and a Gram-negative will appear pink. My results for this test ...view middle of the document...
My test results for this were uninoculated because my bacteria had no change. When bacteria undergo aerobic respiration, oxygen is used as a terminal electron acceptor, where it is converted to water. At the same time, however, Hydrogen peroxide is a highly reactive oxidizing agent that can damage proteins, DNA, and RNA within the cell. To prevent this damage, aerobic organisms produce the enzyme catalase, which enzymatically converts hydrogen peroxide to water and oxygen gas (Chess 447). My results for this test were positive because I did observe bubbling when I added 1-2 drops of hydrogen peroxide making it positive for the Catalase test.
The Citrate test shows whether or not organisms use citrate as their carbon source and also if they use ammonium phosphate as their source of nitrogen, which will produce ammonia as a metabolic byproduct. I did not have a color change or growth for this test; therefore I received a negative result. An Oxidase test determines whether or not a bacterium uses cytochrome c oxidase. In aerobic respiration, the electron transport chain links the production of adenosine triphospate (ATP) to the oxidation of electron carriers such as nicotinamide adenine dinucleotide (NADH) and reduced flavin adenine dinucleotide (FADH2). This process ends with the transfer of electrons to oxygen, forming water (Chess 451). Cytochrome c may be the reason for electrons being transferred to water. When we did this experiment we looked to see if we observed a purple spot, once again, my test was negative.
The next test is the Urease test. Many bacteria, especially Gram-negative enterics, are able to further degrade urea to produce ammonia and carbon dioxide. Urea broth contains urea, a strong potassium phosphate buffer, and the pH indicator phenol red, which is peach colored at pH 6.6 and pink at 8.0 (Chess 489). My test tube was pink, making my test positive. The Hektoen Enteric Agar is used to isolate and culture several types of Gram-negative bacteria. Bile salts are present in this test, which inhibits the growth of Gram-positive bacteria, therefore I had no growth. Lactose, sucrose, and salicin are also included in the experiment. All of these can help Gram-negative bacteria grow and ferment.
When transferring my bacteria to the Mannitol Salt agar, I realized that the plate has two sides making sure that there is no mixed culture because it contains mannitol along with the pH indicator phenol red. The MacConkey agar is normally used to further the growth of Gram-negative bacteria providing information about the gram reaction and ability to ferment lactose. I received a negative result. The Nitrate reduction test is used to show that some bacteria can transfer electrons to nitrogen. I received a negative reaction. Cells of certain bacterial genera contain a waxy substance in their cell walls known as mycolic acid, a complex lipid that inhibits passage of...