In the three previous labs we examined bacteria microscopically. Staining provides valuable information as to bacterial morphology, gram reaction, and presence of such structures as capsules and endospores. Beyond that, however, microscopic observation gives little additional information as to the genus and species of a particular bacterium. To identify bacteria, we must rely heavily on biochemical testing. Since DNA codes for protein synthesis, then different species of bacteria must, by way of their unique DNA, be able to synthesize different protein enzymes .
Enzymes catalyze all the various chemical reactions of which the organism is capable.
This in turn means that different species of bacteria must carry out different and unique sets of biochemical reactions . After incubation, you then observe each medium to see if specific end products of metabolism are present. This can be done by adding indicators to the medium which react specifically with the end product being tested, giving some form of visible reaction such as a color change . The results of these tests on the suspected microorganism are then compared with known results for that organism to confirm its identification. Lab 7 will demonstrate that different bacteria, because of their unique enzymes, are capable of different biochemical reactions.