Next an MSA test was done and the results showed that there was growth but no color change. This illustrates that the unkown bacteria could tolerate high salt concentration but not ferment mannitol. The MSA plate eliminated Streptococcus pneumonia and Streptococcus pyogenes as choices since the bacteria can’t grow in high salt concentration. Staphylococcus aureus could be eliminated because not only did the unknown bacteria grow but also it didn’t change color to yellow. Lastly a Catalase test was done by taking a colony from the Blood Agar plate... ... middle of paper ... ...imary stain and not pick up the counterstain.
The EMB plate was used to isolate the gram negative rod because the EMB plate is selective for gram negative rods, inhibiting the growth of gram positive organisms. This will effectively isolate the gram negative bacteria, thus creating a pure colony. Furthermore, the EMB plate differentiates for a gram negative rod that has the enzyme to break down lactose or sucrose, releasing an acidic waste product. If the organism appears to be dark purple to black, then it means that the microbe can ferment lactose and sucrose. The purple colonies on the EMB plate reveal that the gram negative bacteria is able to ferment lactose and sucrose.
The Catalase Test indicated a positive result. This showed that the bacterium contained the enzyme catalase which converts hydrogen peroxide into water and gaseous oxygen. The positive control used for this test was Micrococcus and the negative control for this test was Entercoccus. The Sulfur Reduction, Indole Production, and Motility (SIM) Test results indicated that the bacterium lacked the enzymes cysteine reductase or thiosulfate reductase and thus was unable to reduce sulfur. The positive control used for sulfur reduction was Proteus mirabilis and the negative control used was Staphylococcus epidermidis.
In this experiment, a series of biochemical test and API 20 E test are carried out to identify the unknown bacterial species provided. MacConkey agar, a selective and differential medium which is designed to isolate and differentiate the gram negative enteric bacteria. Bile salts and crystal violet inhibit the growth of gram positive organisms. Lactose provides a source of fermentable carbohydrate, allowing for differentiation of lactose fermenting bacteria from lactose non-fermenting gram negative bacteria. It uses for differentiate gram negative bacteria between phenotypes with mutations that confer varying abilities to ferment particular sugar.
In order to identify an unknown bacterium a variety of tests can be performed. The unknown bacterium that underwent a few of these tests was determined to be Escherichia coli. A Gram stain, citrate utilization test using Simmons citrate agar, and a urease detection test with phenol red were performed on the assigned bacterium. The unknown bacterium was determined to be E. coli because the tests concluded that the specimen was Gram-negative, bacilli, citrate utilization negative, and urease production negative. It is concluded that E. coli cannot utilize citrate as its sole carbon source and it cannot convert urea into ammonia and carbon dioxide.
Phenolphthalein also did not react to this substance. The pH value was 7, neutral, also adding to the proof that this substance was water, because water is neutral. The substance was clear and odorless, and all of these reactions combined led me to my conclusion of substance A being water. Test-tube B: Test-tube B had spoiled milk in it. The substance reacted to blue litmus paper, and red litmus paper underwent no change.
Sucrose and lactose serve as fermentable carbohydrate sources which encourage growth and allow one to differentiate between fermenting and non-fermenting microbes. Vigorous fermenters of lactose or sucrose will produce quantities of acid sufficient to form the dark purple dye complex which is usually associated with a green metallic sheen. Slow fermenters will produce a smaller amount of acid production and appear brown-pink in color (Lab Handout; EMB). This experiment resulted in no color change which was expected as two previous tests indicated that my unknown was a gram- positive bacteria and this test is selective for gram-negative bacteria.
Based on the fermentation testes the microbe did ferment Glucose, Sucrose, lactose and Maltose. Si... ... middle of paper ... ...ll biochemical tests performed came out as expected except for the starch and urea digestion. On the first test starch shows a false + test and then on the second test it comes as a negative result. The same thing happened with the urea digestion it showed a false + test on the second test as a negative result, matching the result of a known bacterium, staphylococcus aureus.Therefore, it was concluded that unknown #79 was staphylococcus aureus. References Community college of Denver (2014).Introduction to microbiology laboratory manual.Boston,MA;person Learning solution Oxidative/fermentation glucose test.
It was determined using Thioglycollate agar deep the unknown culture was inoculated using a stabbing technique, and it was determined that the bacteria is facultative. The bacterium was also inoculated in glucose phenol red fermentation broth and lactose phenol red fermentation broth. Both tubes started red and the turned yellow if acid is present. So when the bacterium ferments it produces an acid and the phenol red turns yellow. There is also a small inverted tube that is placed inside of the tube which indicates whether gas was produced.
If a strong acid ion is added, the buffer simply replaces it with a weak acid ion, therefore causing little change in the pH of the solution. Household cleaning products usually have some form of a buffer, because otherwise, they would burn skin to touch. As expected, the two sodas were originally acidic, while the soap was basic.