Unknown Lab Report

Introduction

This study was purposely done to segregate a pure culture as well as identifying an unknown bacterium. The isolation and identification was done with the application of all methods, which were conducted and learned previously in the microbiology class. To accomplish the task of identifying the unknown culture, separation, and differentiation of possible bacteria was done based on specified biochemical characteristics. The test performed was used systematically to help in recognizing the various specifics and aid in identifying the unknown culture. The test was used irrespective of whether it identified some specific enzymatic reactions or it identified metabolic pathways.

Discussion

All tests performed on unknown cultures of bacteria were used in determining the bacteria identity. Streaking the unknown bacteria B out onto a plate of Nutrient agar was the first step requiring completion. This step was done based on the streak method as it is described in the lab manual. The plate was incubated, becoming contaminated. The contamination caused the plate with bacteria B to grow resulting to the appearance of the colony and creation of Gram stain. The bacteria in the plate were rod-shaped and purple in color as seen in the Gram stain.

A test was done to establish the presence and fermentation of sugars like lactose and sucrose. This test was done with the use of broth, which contained phenol red and the respective sugar compounds. Inoculation of the broth with the unknown culture of bacteria was done after which the result was incubated for growth. Given a case where the sugar molecules were fermented, the pH level in the tube would go down resulting to the conversion of the phenol red to yellow. This color change indicates that the result of fermentation to be acidic. This case signifies that, when the originally red broth is converted to yellow, the test is positive. The positive test indicates that the bacteria can be fermented with the use of sucrose or fructose. Negative results would be signified by a situation of no color change in the red broth indicating that no fermentation has taken place.

Mannitol salt agar is selective for tolerating salt. It is differential for the fermentation of mannitol sugar. Agar is used for Gram and cocci, and it contains phenol red. The phenol red acts as a pH indicator, since it turns yellow under acidic solutions. Agar is often used in selecting their growth where yellow color signifies positive results. Negative results were not obtained since the ager slightly changed color to yellow after incubation with unknown bacteria culture was done. The color change portrayed a slight fermentation. The test conducted form a basis for concluding that Staphylococcus epidermidis was the unknown culture. Performing a catalase test, for clarification, did not result to any color change confirming that Staphylococcus epidermidis was the unknown bacterium. Wrong results could have originated from contamination of the unknown organism.

Conclusion

Achieving the determination of unknown identities in the tests was possible through various differential tests. The test involved tracking the results to identify the unknown bacteria using previous data on bacteria. Staphylococcus epidermidis was identified as the unknown B.

Staphylococcus epidermidis has Staphylococcus as the genus, and it naturally colonizes mucosa skin of humans. Staphylococcus epidermidis is thus part of normal flora of humans. Most of the bacteria strains are nonpathogenic although they can be pathogenic with the hospital environment. The bacteria are contaminated through medical instrument or skin conduct. Infections resulting from the bacteria include conjunctivitis, urinary tract infection, endocarditis, and meningitis. Vulnerable groups to the infections include people with internal prosthetic devices and those with compromised immune systems. Vancomycin, daptomycin, gentamicin, linezolid, and rifampin formulate the most effective antibiotics.