5 February 2016 Exercise III- Microbiology and Identifying Bacteria Objective"'- the objective of this lab was to observe and identify bacteria based on their motility, gram stain, colony morphology, and sequencing of the 16s ribosomal subunit gene.
Hay Infusion Culture After a week the Hay infusion culture seemed to get lighter in color, with the soil and most of the leaves going to the bottom of the jar. However, there were some lighter in mass leaves that were still floating in the middle and the top. The smell of the Hay infusion culture seemed to worsen, a smell of poop mixed with decomposing material. I hypothesize that the smell and the appearance of the Hay infusion culture changed was because the environment’s pH and amount of material changed. Leading to microorganisms dying and changing. The Archaea did not grow on agar plates because Archaea grows only in extreme environments, which the agar plates did not provide.
Procedure I: Quantifying and Observing Microorganisms When I was recording the plates I had seen a substantial difference in the colony types between the plates with tetracycline and without tetracycline.
10^(-3)- The biggest difference observed was between agar plate with and without antibiotic was observed in this dilution. The agar plate without tetracycline contained a lawn of colonies that were dark green in color. While the agar plate without contained about 203 colonies of rod, yellow like bacteria. 10^(-5)- The colony types were similar between the one with tetracycline and without it. They looked like circular, yellow like bacteria. The only difference observed was that the one with the antibiotic had only one colony, while the one without it had about 130. In both plates Fungi was not observed. 10^(-7)- The agar plate without antibiotic had one rod, yellow like colony. While the one with antibiotic did not have any colonies. 10^(-9)- Interestingly enough the agar plate with tetracycline showed to have a fungi grown on it. While the one without tetracycline did not have anything. Antibiotics can not kill Fungi that why the colony was able to grow on the agar plate with tetracycline.
The observations confirm that the bacteria collected is not fully resistant to tetracycline antibiotic, reducing the amount of the bacteria colonies in those who had an antibiotic. The tetracycline however did not have any effect on the Fungus. Proving that the antibiotics cannot affect Fungal growth.
Mechanisms of Tetracycline
Tetracycline belonging to polyketide class, is widely used against bacterial infections. What it does it releases its promoter into the cell depressing the transcription of the bacterial cell that it had infected (Werten). This afterwards triggers allosteric cascade, even in the absence of magnesium, stopping bacterial protein synthesis. The bacterias that are sensitive to such antibiotic are bacterial pathogens such as Chlamydia, Mycoplasma and Rickettsia (Werten).
Werten, Sebastiaan, et al. "Tetracycline Repressor Allostery Does Not Depend On Divalent Metal Recognition." Biochemistry 53.50 (2014): 7990-7998. Academic Search Premier. Web. 5 Feb. 2016.
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