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How to Identify Unknown Bacteria

This activity was performed in order for us to identify two unknown bacteria supplied to us by our instructor. With the use of differential tests and culture media, we were able to recognize and classify these two microorganisms. Each test provided us some key information pertaining to the specific bacterium studied. Differential tests such as SIM, Citrate, Phenol Red, Urease and Triple Sugar Iron tests were utilized in this laboratory exercise. Strict sterile techniques were followed and practiced all throughout the procedure in order to obtain accurate results.

The results of these tests showed that the two unknown bacteria being studied are: Streptococcus pyogenes and Micrococcus luteus. This laboratory exercise enabled us to practice and exhibit our skills in handling bacteria as well as utilizing our expertise in carrying out various tests. It also enabled us to build up problem solving abilities in order to come up with the two unknown bacteria. Introduction Bacteria are unicellular microorganisms that can be identified thru their morphological structures and other differential tests.

They play a very significant function in nature. Most of them are harmless, however, many causes illnesses. Bacteria prefer banding collectively in organized, structured and mutual communities called biofilms (Ben-Ari, 2008). These microbial communities are accountable for many chronic infections and diseases. Identification of unknown bacteria in the laboratory aids in planning and establishing therapeutic regimen to fight the specific microorganisms. Culturing a specific species of bacteria also could be done with the knowledge of their exact identification and classification.

Bacteria had been used and utilized as antibiotics to combat specific infections (Canu, 1997). Streptococcus pyogenes are the primary bacterial offenders for sore throat, other skin infections like impetigo. They are also the cause of necrotizing fasciitis or commonly known as the flesh eating disease. When these bacteria invade the bloodstream, it could cause toxic shock which is very fatal (Brown, 1997). These common microorganisms survive only in humans and is contagious.

Prompt antibacterial medications and treatment is needed to stop infection. Micrococcus luteus thrives in mammalian skin and is part its normal flora. Although this bacterium is non pathogenic, it colonizes the human mouth, oropharynx and upper respiratory tract. This bacteria were isolated from the tongue, tooth plaques (supra gingival plaques) as well as gum edges. They feed on smelly breath (Biotech Week, 2005). Techniques regarding sterile techniques and doing pure cultures were already established prior to doing this laboratory exercise.

Gained knowledge on bacterial strains, and their pathogenic ability are also essential. It is imperative to be cautious and careful when handling microorganisms at all times. Materials and Methods Unknown bacteria are given by the instructor. The first step performed was the preparation of the culture medium. The bottom of the Petri dish was labeled with the bacterium number. All the culture media needed in order to identify the two unknown bacteria given will be made.

The bacterial media were as follows: SIM medium, MR-VP medium, nutrient broth, nutrient agar, nitrate broth, nitrate agar, Simmon’s Citrate Agar, Phenol red dextrose/ lactose broth. Biochemical tests including phenol red carbohydrate, catalase production, oxidase production, methyl red test, citrate utilization and tryptophan hydrolysis were done. SIM medium is a combination differential medium which is represented by three parameters: sulfur reduction, indole production and motility. Simmons citrate agar is used to test the ability of the bacteria to use citrate as a carbon source.

This media contains sodium citrate as the only source of carbon and ammonium hydrogen phosphate as the single source of nitrogen. Its pH indicator is the bromthymol blue. Phenol Red Broth is used to differentiate gram negative bacteria. Phenol red is used a pH indicator as it contains peptone. Triple sugar iron test is a differential medium containing lactose, sucrose, a small amount of dextrose, ferrous sulfate and phenol red as its pH indicator. This is used to differentiate enteric bacteria based on its aptitude to decrease sulfur and ferment carbohydrates.

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