IntroductionThe objective of this lab was to identify cultures of unknown bacteria using various differential tests. There are many reasons to know the identity of microorganisms, including finding the correct antibiotic to treat infections that the bacteria may have caused. All methods and techniques used to identify unknown bacterium no. 79 were learned in the microbiology laboratory. Test Result The Stranger No. 79 was grown on a TSA inclination at a temperature of 370 C after two days, the microbe replicated into more than 100 microorganisms, which has cream-colored pigments and convex prospects. The microbe entire margins and convex reliefs. The microbe appears to be circular and 0.4-0.7 micrometers in diameter. Crystal violet, iodine, alcohol, and safranin were used to determine the Gram stain of unknown no. 79 as Gram-positive bacteria. Under the microscope with 100x oil lens, the microbe was seen as a cluster formed in the shape of a coconut. The motility of the bacteria was detected by growing the bacteria in a special type of nutrient agar, the test was performed in a deep tube containing the motility medium. We stick it with an inoculation needle in a straight line in the center of the depth, and the bacteria only grow along the inoculation line, which shows that the bacterium is not motile. Thioglycolate broth is a multipurpose, enriched, differential medium used primarily to determine the oxygen requirement of microorganisms. In this test the growth was everywhere but it was better at the top so this determined that unknown #79 is facultative anaerobic. The fermentation test is performed to detect the ability of microorganisms to ferment a specific carbohydrate. Based on fermentation tests the microbe fermented glucose, sucrose, lactose and maltose. Yes... half of the paper... All biochemical tests performed gave results as expected, with the exception of starch and urea digestion. On the first test the starch shows a false + test and then on the second test it comes back negative. The same thing happened with urea digestion: it showed a false + on the second test as a negative result, corresponding to the result of a known bacterium, staphylococcus aureus. Therefore, it was concluded that unknown no. 79 was staphylococcus aureus. ReferencesCommunity college of Denver (2014). Introduction to the microbiology laboratory manual. Boston, MA; learning solution per person Oxidative/fermentative glucose test. (2014, April 15). Retrieved April 23, 2014, from Wikipedia: http://en.wikipedia.org/wiki/Oxidative/fermentation_glucose_testGelatin hydrolysis test. (n.d.). Retrieved 4 22, 2014, from http://www.vumicro.com/vumie/help/VUMICRO/Gelatin_Hydrolysis_Test.htm