User:Lynda Gabriela Arostegui/Notebook/Biology 210 at AU
Hay Infusion (January 28, 2016)
The smell of our culture this week was much stronger than the week before. The water also appeared less unclear and more dirty. To add, the film that was on the top layer of the container was also thicker and a film also lined much of the plant life. The changes observed from last week to this were probably due to the further reproduction of the microorganisms. Archaea will not have grown on the agar plates, because the environment was not severe enough. Archaea cultivate in extreme temperatures, which is why they can be found in hot springs.
Colonized Bacteria (January 28, 2016)
This week we observed the petri dishes (pictured above) we plated last week with diluted samples from our Hay Infusion Culture. We plated some samples with an antibiotic, tetracycline, and others without. As expected, or hoped for at least, the plates which were treated with tetracycline had fewer colonies, as opposed to the the plates without treatment. Thus, for the plates treated with antibiotics to have grown any bacteria, means that in the plate were antibiotic resistant bacteria. So the tetracycline killed off the "weakest" bacteria, and by the process of natural selection, antibiotic resistant bacteria grew in the dishes as they outlived the other and then reproduced, passing on their "fittest" genes; this still accounts for why these plates had far less colonies. The plates treated with antibiotic and diluted 10^-6 and 10^-8 grew no bacteria. These samples had minimal bacteria, meaning they also had less variability and the antibiotic had the best chance to work fully.
The following table shows how many colonies grew on each of the eight plates.
Mechanisms of Action for Tetracycline (January 28, 2016)
Tetracycline is an antibiotic that was discovered in the 1940s. It can work against organisms like chlamydiae, mycoplasmas, and rickettsiae, and protozoan parasites by limiting their protein synthesis. Tetracycline prohibits the attachment of tRNA to its acceptor site (Chopra). So without protein synthesis, amino acids cannot be processed and carry out their many functions.
Chopra, Ian, and Marilyn Roberts. “Tetracycline Antibiotics: Mode of Action, Applications, Molecular Biology, and Epidemiology of Bacterial Resistance.” Microbiology and Molecular Biology Reviews 65.2 (2001): 232–260. PMC. Web. 4 Feb. 2016.
Examined Organisms (January 28, 2016)
The first organism examined came from the plate diluted 10^-2 and had tetracycline. On the plate, it appeared circular with an entire edge and a convex surface. It also had an orange color. Under the microscope, the bacteria appeared to be round and green with motility, like the other samples, and was gram-negative (refer to Fig.1). The second organism also came from the same plate, however it was filamentous and white. It had an umbonate surface and was dry and powdery. This bacteria also looked round and green under the microscope, and was gram-negative. The third sample examined was extracted from the plate diluted 10^-4 and did not have tetracycline. From the naked eye, the bacteria appeared to be circular and whole with a convex surface and clear color. Under the microscope, the organism appeared to be very tiny. It was round and green, and the staining revealed it was gram-positive, as it can be seen in Fig. 2. The last sample observed was taken from the plate diluted 10^-6. As noted in the plate, this bacteria appeared to be circular, whole, smooth, and was raised. Like the other bacteria, this one was also very tiny and green with motility. The staining demonstrated that this bacteria was gram-postive.