Background
The purpose of this experiment is to make the students aware of the terminology used by microbiologist and professionals in related fields to describe their findings during research. The methods used to describe characteristics of microorganism need to be uniform to allow other scientists to readily interpret the work of others. The identification of the cultural characteristics of an organism allows the researcher to determine the possible taxonomic classification of the organism (Cappuccino 29).
Materials and Methods
To complete this experiment, we used three different types of cultures: nutrient agar slants, nutrient agar plates, and nutrient agar broth. The nutrient broth was a Trypticase soy broth culture. The agar plates were made in an earlier lab to save time and allow us to complete all the work in this lab.
We inoculated the slants using aseptic technique. We started by turning on the Bunsen burner and lighting it with striker provided in the microbiology kit. First we picked up a tube containing M. luteus. Then we picked up a slant pre-labeled with M. luteus and put it in the same hand. With the other hand we picked up the inoculating loop and flamed it until the wire was red. Subsequently, using the same hand that the sterile loop was in we uncapped the tube containing M. luteus and flamed the necks of both tubes by passing them through the flame of the Bunsen burner quickly three times. Using the sterile loop we took a loopful of the inoculum and put it on the slant by zigzagging the loop up from the base of the slant. Then we flamed and capped both tubes and flamed the inoculating loop. After that we put the tubes back in the holder and put the loop back in the box.
We completed these same procedures again using E. coli in the place of M. luteus.
This time we inoculated the plates using the four-way streak-plate technique. We started by labeling all of our streak plates and dividing it out into quadrants with the wax pencil. First, we flamed our inoculation loop until it was red. After this we let it cool for about fifteen seconds and then took a loopful of the M. luteus and streaked it across the first quadrant like we were coloring in cursive. Then we flamed the loop again and let it cool for about fifteen seconds. Using the sterile loop we dragged the M. luteus from the first quadrant to the second quadrant and streaked it across that quadrant in the same manner as the first. Once again, we flamed the loop and let it cool a bit and then used it to drag the M. luteus from the second quadrant to the third quadrant and streaked it across that quadrant in the same manner. Once again, we flamed the loop and let it cool a bit and then used it to drag the M. luteus from the third quadrant to the fourth quadrant and streaked it across that quadrant in the same manner.
We completed these same procedures again using E. coli in the place of M. luteus.
This time we inoculated the broth cultures using aseptic techniques. With a pre-labeled tube and a tube of M. luteus in hand, we were ready to begin. With the other hand we picked up the inoculating loop and flamed it until the wire was red. After that, using the same hand that the sterile loop is in we uncapped the tube containing M. luteus and flamed then necks of both tubes by passing them through the flame of the Bunsen burner quickly three times. Using the sterile loop we took a loopful of the inoculum and put it in the broth stiring lightly to ensure that the inoculum would get in the broth from the loop. Then we flamed and capped both tubes and the inoculating loop. After that we put the tubes back in the holder and put the loop back in the box.
We completed these same procedures again using E. coli in the place of M. luteus.
With the completion of our lab for the day, we put the tubes of E. coli and M. luteus in the bio bucket. We put all of our inoculations in the thirty seven degree Celsius incubator, put up the supplies and wiped down our area with bleach.
The cultures were incubated for a period of 48 hours and then transferred to a refrigerator.
Results
Streak plate
Growth on the slant
Broth culture
The results of this experiment allowed us to practice classifying the characteristics of microbial growth on a common culture. We came back to class for the following lab and took our cultures out of the refrigerator. Using the growth on the mediums, we documented the type of growth based on the graphs provided in the lab manual.
Conclusion
During the course of this lab, we learned many of the terms required to classify microbial growth. After the growth on the medium we had to use the terms to describe the abundance of growth, pigmentation, optical characteristics, form, and consistency. Our data compared favorably towards other groups in the lab. The only inconsistency we seemed to have was lack of growth on a nutrient agar slant. We think that this was because we did not let the inoculation loop cool long enough to not destroy the microorganisms we were trying to inoculate. We fixed this by using a timer to make sure that we let the loop cool long enough. A major improvement to all the labs would be to allow more time for the labs to be completed. Most of the labs we have to rush to get everything completed on time.
Works cited
Cappuccino, James, and Natalie Sherman. Microbiology: A Laboratory Manual. Tenth Edition. Boston: Pearson, 2014. Print.
Last updated on 7-April-2014 at 2:29 PM
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