Spectrophotometer Lab Report

placed in a spectrophotometer. The data collected was used to view the growth of the bacteria and can be used to compare the growth of this E. coli strain to other E. coli strain, bacteria and the general bacterial growth curve. The data collected can make a template to possibly classify unknown bacteria. Not all bacteria replicate and grow at the same rate. Processes such as gram staining can be used in conjunction with monitoring the growth of a bacteria to further reinforce a hypothesis.
Materials and Methods:
Materials
Streptomyces and Antibiosis
The following materials and apparatus were used to complete the study of Streptomyces and its antibiotic properties. Soil samples were collected from the pond on the Brooklyn College campus,…show more content…
A spectrophotometer was used to monitor the growth of E. coli over a 180-minute period. Spectrophotometers uses light to measure the optical density of a solution, based on the solutions turbidity. Certain wavelengths of light are used for different bacteria and solutions. To measure the optical density of reproducing E. coli, an optical density, (OD) of 600, OD600 was used. To grow the E. coli, 190ml of 2% glucose nutrient media was added to a 250nl Erlenmeyer flask. 10ml of nutrient media was used to blank the spectrophotometer set at OD600. 10ml of E. coli stock culture were added to the 190ml nutrient media, creating a 1:20 dilution. The inoculated nutrient media was then placed into a 37C orbital shatter to incubate. All solutions measured with the spectrophotometer were placed in spectrophotometer tubes. To count the E. coli cells, cells were dyed with crystal violet. A Pasteur pipette was used to transfer the dyed cells to a hemocytometer which was then placed on the stage of a brightfield…show more content…
The pond is adjacent to the Brooklyn College Library and Ingersoll Hall. Prior to the execution of this experiment, the soil sample was mixed with 10ml of sterile water. No water was present during the completion of this exercise. Sterile technique was implemented and used for the remainder of the experiment. The cap of a centrifuge tube was used to collect approximately one (1) gram of soil from the sample. This was then added to a bottle containing 99ml of sterile water for a 10-2 dilution, 1ml of 10-2 dilution was then added to a bottle containing 99ml of water for a 10-4 dilution. 1ml from the 10-4 dilution was then added to 99ml of water for a final dilution of 10-6. 1ul of each was plated on different starch agar plates with the aid of a micropipette and a plate spreader. The plates were then incubated for a week. Following incubation, each plate was observed, and putative Streptomyces colonies were identified. Colonies were identified based on phenotypic qualities. Colonies that appeared, “fuzzy” powdery, leather like, raised and or pigmented colonies were identified as putative Streptomyces colonies. A putative colony was subjected to a gram stain. 3-4 drops of E. coli, cultured in solution was added to molten agar and placed on a nutrient agar plate to solidify. This was repeated two more times with a second and third., nutrient agar plate. This was due to the uneven