Unknown Paper

Topics: Gram staining, Staining, Bacteria Pages: 7 (2815 words) Published: December 1, 2010
The objective of these “unknown” experiments was to take a mixed culture, which contains two unknown species, and identify those species through a series of tests. The group was informed that one species of bacteria would be a gram-negative bacillus and the other would be a gram positive coccus. The tests to be conducted ranged from streak plate isolation to biochemical tests. Each test to be conducted was discussed and agreed upon by all group members. The results of each test were analyzed by the group and led to selection of the next test that would further narrow the possible identity of the unknown species. On September 16, 2010, our group was given a mixed culture in which we were to identify two organisms within the mixture, by running several biochemical tests. On this day our objective was to prepare the specimen of the mixed culture into discrete colonies. Each member of our group then conducted a streak plate and we would later pick the best plate of isolated colonies. To perform a streak plate, aseptic technique was required. We had our mixed culture in the form of a broth therefore our inoculating instrument would be a loop. We also needed our agar plates each marked into four quadrants and a Bunsen burner. We then proceeded to transfer the mixed culture to the plates aseptically. In preparation for the transfer of the mix culture to a plate we placed the tube of broth in our non-dominant hand. The loop was sterilized by placing it into the fire of the Bunsen burner until the entire wire became red hot, “red is dead”. The tube was uncapped facing the cap downward along with the inoculated loop in the dominant hand. We then passed the tube through the flame of the Bunsen burner briefly to burn off any contaminates that may be present at the opening of the tube. The inoculated loop was then inserted into the broth of the mixed culture to obtain the organisms to be transferred to the plate. The tube was then passed though the Bunsen burner again, capped, and put aside. With the sterilized loop containing the organism we proceeded to transfer the organism to the plate of quadrant I in a zigzag movement. We then re-flamed the loop till red and cooled the instrument to the side of quadrant II. Then from quadrant I we made four lines crossing into quadrant II. We re-flamed the loop till red and then cooled the instrument again to the side of quadrant III. From quadrant II we made four lines crossing into quadrant III. From quadrant III we continued making four more lines crossing into quadrant IV. We inoculated our loop once more, freeing the instrument of any organism by re-flaming till red. Once we each completed a streak plate, the plates where taped and marked with the date, initials, and group number.

On September 23, 2010, we obtained our plates made from September 16. We identified discrete colonies into two organisms that we named yellow and beige. The yellow organism was an obvious yellow pigmentation, moderate in size, entire, circular, raised colony and the beige was an off-white pigmentation, small, entire, circular, umbonate colony. We next chose the best representative colony of each organism to be transfer to a nutrient agar slant. Again we aseptically transferred the organisms, yellow and beige, into individual agar slants. Our instrument that we used was a loop along with two slant tubes and a Bunsen burner. With our selected plate ready and available, the slant in the least dominated hand, we inoculated the loop till red, uncapped the tube, flamed the tubes, obtained the yellow organism from the plate, and transferred it to the slant in a zigzag motion. We then re-flamed the tube, capped the test tube, and flamed the loop. Then we proceeded with the same procedures for the beige organism. The purpose of transferring the organisms was to evaluate the abundance of growth, pigmentation, optical characteristics, form (not applied due to the use of a zigzag rather then a straight line), and...
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