The identification of the unknown bacterium was determined through a series of tests using differential media and a Gram stain. These tests revealed information about the motility, metabolism and enzymes of the unknown microorganism. The most basic technique for all tests is called the aseptic technique. This technique serves to “prevent sample contamination” (Leboffe and Pierce, 2010). This is the first technique taught to students in the laboratory. Aseptic transfers were performed with an inoculating loop or needle between the stock of microorganisms on sterile medium. Sterile media included tryptic soy broth or tryptic soy agar. To prevent contamination, inoculation loops and needles are usually sterilized in a Bunsen burner flame, but a micro-incinerator has been used in the laboratory instead. Other measures taken to avoid contamination include holding an open test tube at an angle and heating the edge of the test tube and the surrounding air (Leboffe and Pierce, 2010). A microscopic examination was usually combined with a stain. For example, a Gram stain can be used to identify the shape of the microorganism and the number of peptidoglycan layers it has. The cell shape and type can be used to determine which genera unknown bacteria might be classified into. Differential means have been used to “distinguish different species of bacteria” (Madigan, Martinko, Stahl, Clark, 2012). Although all species of bacteria are capable of surviving in soil, there are visible differences. Selective media were used to promote the growth of specific bacterial species while inhibiting others. Differential and selective media provide more information than normal media. To distinguish a positive from a negative result for a test, both positive and negative controls are needed because the results can be varied. There is no correct species concept for bacteria. The most widely accepted concept groups species “on the basis of overall genomic similarity and sharing of phenotypes deemed ecologically important” (Vos, 2011). This concept is different from the biological species concept used for eukaryotes. The biological species concept defines a species as a group of organisms in a population capable of interbreeding and producing viable offspring in nature. Species of bacteria do not undergo sexual reproduction, making the biological species concept inadequate for defining a species of bacteria. Another aspect of bacteria that makes it difficult to define the species concept is the ability of prokaryotes to perform horizontal gene transfer.