Lab Report
Microbiology Laboratory Report
Identification of Unknown Bacteria
03/10/05- 04/01/05
Authors: Richard Hendricks, Jessica Prebish; NMU
Abstract:
Broth culture 16 was randomly selected by our group and subjected to qualitative tests for taxonomic identification. The culture did appear homogenous throughout the testing period and is currently retained by Northern Michigan University’s department of Microbiology. We suggest that culture 16 is an example of Escherichia coli.
Background:
Techniques used were in accordance with NMU Professor Dr. D. Becker’s lab manual (ISBN 0-390-53911-
2; McGraw Hill). Changes in protocol or interpretation are noted where they were implemented, but strict adherence to the manual prevailed.
Materials and Methods:
Microscope, incubator, and deionizer functioned correctly throughout testing period, with stains, dishes, agars, and test reagents readily available. Lab procedures are considered orthodox and usage thereof is noted chronologically.
3/15/05
We obtained a 24 hour old stock broth culture of the unknown specimen 16. It appeared turbid, reflecting a substantial amount of growth. To determine that the stock culture was pure, we performed a streak plate using loops of the stock broth on a fresh dish of nutrient agar and then incubated it for 48 hours at Standard
Temperature and Pressure; 37C, 1 ATM (STP).
A Gram stain was then carried out to differentiate the unknown sample from a broad class to a more specific category of bacteria. The Gram stain distinguishes between Gram-positive and Gram-negative bacteria based on the composition of the cell walls. Gram-positive bacteria appear purple and Gramnegative bacteria appear pink after staining. The first Gram stain produced unsatisfactory results and was then repeated with a clear indication of negativity. Light pink staining was evident on the cells in the field of view (FOV) and a search of the slide revealed uniformity in the sample. From these results we
Identification of Unknown Bacteria
03/10/05- 04/01/05
Authors: Richard Hendricks, Jessica Prebish; NMU
Abstract:
Broth culture 16 was randomly selected by our group and subjected to qualitative tests for taxonomic identification. The culture did appear homogenous throughout the testing period and is currently retained by Northern Michigan University’s department of Microbiology. We suggest that culture 16 is an example of Escherichia coli.
Background:
Techniques used were in accordance with NMU Professor Dr. D. Becker’s lab manual (ISBN 0-390-53911-
2; McGraw Hill). Changes in protocol or interpretation are noted where they were implemented, but strict adherence to the manual prevailed.
Materials and Methods:
Microscope, incubator, and deionizer functioned correctly throughout testing period, with stains, dishes, agars, and test reagents readily available. Lab procedures are considered orthodox and usage thereof is noted chronologically.
3/15/05
We obtained a 24 hour old stock broth culture of the unknown specimen 16. It appeared turbid, reflecting a substantial amount of growth. To determine that the stock culture was pure, we performed a streak plate using loops of the stock broth on a fresh dish of nutrient agar and then incubated it for 48 hours at Standard
Temperature and Pressure; 37C, 1 ATM (STP).
A Gram stain was then carried out to differentiate the unknown sample from a broad class to a more specific category of bacteria. The Gram stain distinguishes between Gram-positive and Gram-negative bacteria based on the composition of the cell walls. Gram-positive bacteria appear purple and Gramnegative bacteria appear pink after staining. The first Gram stain produced unsatisfactory results and was then repeated with a clear indication of negativity. Light pink staining was evident on the cells in the field of view (FOV) and a search of the slide revealed uniformity in the sample. From these results we
References: Benson-Brown, Amy (2001) Microbiological Applications Lab Manual; Complete version, 9e Harley, John (1996) Laboratory Exercises in Microbiology, Sixth Ed. J.G. Holt, Lippincott, Williams and Wilkins, 9th ed. (1994) Bergey’s Manual of Determinative Bacteriology Kleyn, J