INTRODUCTION The purpose of this investigation was to identify an unknown bacterium. “At any moment there are millions of bacteria living around, on or inside us” (The Plague). The bacterium cannot be identified simply by looking at it. Many bacteria have similar aspects of growth. “In most cases, detection is based on the reaction of an enzyme with a certain substrate” (Sigma-Aldrich). Identification is usually based on findings of the metabolic capabilities of the bacterium's cells. Some bacteria are harmless and part of our normal flora. While other bacteria are capable of causing illness or death. To determine what type of bacteria is present, a series of biochemical tests must be performed. Biochemical tests mean the ability to identify the bacterium responsible for causing diseases or pathologies. Once this is determined, other tests can be performed to find out which treatments would work best to eliminate the disease-causing bacteria. During the investigation, seven tests were used to determine the unknown bacterium as Salmonella typhimurium. “Salmonella typhimurium is a genus of medium-sized, rod-shaped, gram-negative, non-lactose-fermenting bacteria belonging to the family Enterobacteriaceae, most species having flagella and pili” (medical dictionary). This bacterium is known to cause food poisoning. These illnesses usually last 4-7 days. Treatments for diseases caused by this bacterium depend on the severity of symptoms, the patient's age and comorbidities. MATERIALS AND METHODS During this investigation to identify the unknown bacterium, seven different biochemical tests were performed. All biochemical tests were performed according to the Eastfield Microbiology Laboratory manual. As is the case with... half of the paper... health problems, the symptoms may be more severe.REFERENCESMicrobiology Laboratory at Eastfield College. (2013). [Comparative table of biochemical test results]. Unpublished raw data. Eastfield College Microbiology Laboratory Manual, 1st edition, Oliver, TD (Book must be purchased new from the Eastfield Bookstore and may not be resold to the bookstore at the end of the semester), Kendall Hunt Publishing, 2013, Dubuque, IA. ISBN 9781465223784. Microbiology with Diseases by Body System (hardcover) and MasteringMicrobiology, 3rd edition, Bauman, RW, Benjamin-Cummings Publishing Company, 2012, San Francisco, CA. ISBN 9780321716378. OR Cefrey, Holly. The Plague. New York: Rosen, 2001. Print. http://www.sigmaaldrich.com/analytical-chromatography/microbiology/identification-tests/reagents.html 2013 “Welcome to Microbugz.” Welcome to Microbugz. Linda Beaver and Mary Rutter, web. 2000