The purpose to this lab was to isolate and identify two unknown bacteria from a mixed culture provided to us by our instructor. This study was done by applying all of the methods that have been instructed on thus far in microbiology laboratory class. Each test performed, provided us with some key information about the unknown microbes in question and how the bacteria function.
Materials and Methods
Over a two week period, eight prepared types of test media were provided to identify the assigned unknown mixed cultures. Not all of these tests were performed on every culture, as some were used only for gram positive or gram negative bacteria. The tests performed and what constituted a positive or negative test are as follows:
Lab day 1; today in lab we obtained the unknown mixed culture “041”and one brain-heart infusion agar (BHIA). The first step was the preparation of the medium, the bottom of the BHIA dish was labeled with the bacterium number, initials, and section; then divided into four quadrants. The second step, we used the septic technique to transfer a small amount of culture with a flame-sterilized inoculating loop to the first quadrant, flamed and cooled the loop again then transferred a small amount of the culture from the first quadrant to the second using the quadrant streaking method as illustrated on page 18 of the lab manual, repeating this process until all four quadrants were properly streaked.
Lab day 2; we collected our BHIA medium and began by identifying the morphology and cell-to cell arrangements of the colonies. Two different colonies were observed, the first colony was yellow in color and larger in size and the white colored colony was slightly smaller in size. As instructed, each colony was prepared for gram staining, one slide for the large yellow colony and one for the smaller white colony. After properly gram staining the slides as directed in chapter six of the lab manual, the smears were examined... [continues]
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