Microbiology

Micrococcus luteus 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 were Gram-positive cocci.  A capsule stain is preformed to see if the bacteria cells of some species are protected against harsh environmental conditions. A capsule is a complex layer of sugars and proteins called a capsule (Chess 325). Results for my experiment came out negative for this test; therefore I did not observe capsules. An Endospore stain may also be done testing for spores that provide protected structures that allow the cell to survive harsh condition. Most bacteria cannot live if conditions are not right for them. For example temperature is a huge factor in bacteria growth.  I received a negative result, in other words, my bacteria has no spores.  My bacteria are also resistant to the antibiotics Ampucillin and Bacitracin.   An Eosin Methylene Blue (EMB) agar is used for the detection of enteric bacteria in dairy products and foods; this test uses two dyes, eosin and methylene blue, to suppress the growth of Gram-positive organisms (Chess 391)  Because my bacteria are Gram-positive, I had no growth for this test. Kligler’s iron agar (KIA) contains a small amount of glucose and a much larger quantity of lactose as well as a pH indicator that signifies the production of acid resulting from the fermentation of either sugar (Chess 415). 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 aqueous dyes through the cell wall (Chess 339). The Acid-Fast stain shows if this is true for certain bacteria. My result was negative. Lastly, there were no usual patterns to my bacteria, such as, swarming or feathering. I had no green or amber diffusible pigment in agar. My test dealing with fermentation of sucrose, dextrose, and lactose were all negative and I did not get a red-ring so there was no indole produced. There are many interesting facts about Micrococcus luteus. The bacterium belongs to the family Micrococcaceae. It has been associated with the spoilage of fish products and it also degrades the compounds in sweat into one’s producing unpleasant odors. Some strains of Micrococcus luteus may occasionally be opportunist pathogens causing septic shock, pneumonia, and urinary tract infections in an immune-deficient person. Its biohazard level is one and its growth temperature is twenty-six degrees Celsius. It may be referred to as milk micrococci and can result in spoilage of milk products. The bacteria are most commonly found in mucous membranes such as the nasal cavities, the lining of the mouth, etc. It may also be found in dust, soil in air that we breathe, and is part of the human skin flora. M. luteus cannot survive long even in these conditions. Because it is on skin and in the nasal cavity, it may be over looked as a source of a clinical infection. Breaking down the words of the bacteria: Micrococcus luteus allows us to understand what the bacteria represent. The prefix micro meaning microbe and coccus which stands for the organism’s spherical shape. The second portion of the name: luteus stands for yellow. Because Micrococcus luteus is so easily overlooked that it has caused several deaths in immunocompromised children (caused by leukemia) from pulmonary hemorrhages because of Micrococcus. From other sources Micrococcus luteus has also been discovered to aid in recurrent bacteremia, septic arthritis, endocarditis, meningitis, and intracranial suppuration. Even with these problems being found and known to be caused by Micrococcus luteus, there is no vaccination to aid in escaping these issues. Micrococcus luteus is known to be Gram-positive cocci. It is arranged in either diplococci or tetrads; I noticed mine to be tetrads. A key to this bacterium is the bright yellow colonies, which was very obvious in my experiment. Also it is not known for spores and is non-motile. There is growth on the mannitol salt agar, but does not ferment. Non-hemolytic (gamma), catalase positive, and it is also nitrate reduced. I found all of these items to be true throughout my process with Micrococcus and that has led me to know that I have found my bacteria! References: http://www.thelabrat.com/restriction/sources/Micrococcusluteus.shtml http://en.citizendium.org/wiki/Micrococcus_luteus http://microbewiki.kenyon.edu/index.php/Micrococcus