Introduction
Bacteria are omnipresent, found in all ecosystems, in any kind of biological community and even under the most extreme conditions where normal human habitation is impossible. They can be found thriving in the subfreezing temperatures of the North Pole while others can be found even in highly acidic solutions like vinegar.
The explanation for such natural profligacy is the vast number of enzymes available to bacteria. While no single bacterium excretes all possible enzymes, every species characteristically produces one or several of these. Microbial Physiology, the branch of microbiology responsible for the study of these enzymes, employs a spectrum of tests that detect the known set of enzymes unique to each species of microbe. This is a potent, indirect approach to identifying a bacterium species in any unknown sample.
Objectives
- To acquire a microbial specimen from its natural habitat and culture it for microbial testing.
- To identify the unknown microbe using a series of physiological tests
Method
We took the specimen from tap water and plated the bacteria into media using multiple interrupted streaking. Streaking facilitates the taking of pure cultures from isolated colonies for future plating. After culturing the bacteria in multiply plates, we commenced testing beginning at approximately 24 to 48 hours of growth. The tests we ran were those for glucose, lactose, Mannitol, H2S, Nitrate reduction, starch hydrolysis, oxidation, decarboxylase testing, urease production, indole production, Methyl red, V-P, and motility.
Results and Discussion
Employing both morphological examination and the battery of physiological tests, we determined the microbe to be Micrococcus luteus. The specimen showed negative results to Indole, Methyl red, starch hydrolysis and ornithine decarboxylase testing. It also proved to be nonmotile in nature. However test results for catalase, urease, oxidase, citrate production, and gelatin hydrolysis proved to be positive. Under the microscope with a magnification of 97 – 100x oil immersion, the microbe proved to have no endospores and prominent morphological features were the tetrad pairs of cocci shape.
Conclusion
Taking into consideration the results of the experimental screening series, we conclude that physiological tests are the methods best suited to identifying unknown microbes. No one bacterium can survive all these conditions and use all nutrients available (Pollack et al., 2005, 108) since every species of bacteria is limited to a unique set of enzymes. Hence, physiological identification provides species-specific results, whereas morphological identification is limited by the fact that many bacteria species share morphological features.
Works Cited
Pollack, Robert et al. “Laboratory Exercises in Microbiology” John Wiley and Sons, Inc, 2005.
Madigan, Michael et al. “Biology of Microorganisms” New Jersey: Pearson’s Education, Inc, 2003.