There are many reasons for knowing the identity of microorganisms. The reasons range from knowing the causative agent of a disease in a patient, so as to know how it can be treated, to knowing the correct microorganism to be used for making certain foods or antibiotics. This study was done by applying all of the methods that have been learned so far in the microbiology laboratory class for the identification of an unknown bacterium. Broth culture #72 was randomly selected and subjected to qualitative tests for identification. It is suggested that culture #72 is an example of Serratia marcescens and Micrococcus luteus. There were ten bacteria species possibilities: Stahylococcus epidermidis, Bacillus subtilis, Escherichia coli, Serratia marcescens, Sarcina lutea, Pseudomonas fragi, Micrococcus luteus, Alcaligenes faecalis, Clostridium sporogenes, and Micrococcus roseus. There were several qualitative tests that could be conducted to determine the identity of the unknown species, for example, Gram staining, Fermentation, Catalase, Oxidase, Starch Hydrolysis, Litmus Milk, MOI medium, and the Gelatin Test. All tests and techniques used were performed in accordance with The Microbiology Lab Manual.
Materials and Method: A stock broth culture of the two unknown species #72 was obtained. Two streaks were performed using loops of the stock broth on a fresh dish of nutrient agar and incubated for 48 hours @ 32C and @ 25C. There was separate colony growth that where two different colors one red and one yellow on the streak plate incubated @ 25C. Two slants where made with each colony growth and incubated for 48 hours @ 25C. A Gram stain was then carried out to differentiate the unknown samples. The Gram stain produced satisfactory results with a clear indication that the yellow species was Gram positive and the red species was Gram negative. The Gram stain was conducted to reveal
References: 1. Sigmon, J. Bio 225: Microbiology Lab Manual, York Technical College, 2004, pp. 1-58 2. http://microbewiki.kenyon.edu/index.php/MicrobeWiki