User:Catherine Anania/Notebook/Microbiology and Identifying Bacteria with DNA Sequence

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Lab 3

The objectives of this lab were to understand the characteristics of bacteria, observe antibiotic resistance, and to understand how DNA sequences are used to identify species.

In this lab, we observed the bacteria that was grown on from our Hay Infusion cultures that were made in the previous class. It is unlikely that an Archaea would have grown on the agar plants, since archaea are known to live in very extreme conditions, while we collected our sample from a very temperate transect.

When observing the agar plants, the appearance and smell might change week to week due to the rapid growth of the bacteria. We only waited two days before observing the agar plants, but had we waited longer, there would likely be far more colonies of bacteria present and a much stronger smell.

Image:serialdilutionbac1.jpeg

The agar plates where the antibiotic was present had a lower growth of bacteria compared to those with an absence of antibiotic. Thus, the antibiotic did limit the bacteria to an extent, but by no means eliminated it. A significant number of bacteria were able to resist the antibiotic, presumably due to the high rate of reproduction and short life cycle, which allowed mutations to occur, making some of the bacteria immune to the antibiotic. There may have also been bacteria present that were immune to tetracycline. Bacteria resistant to tetracycline include Staphylococcus spp., Streptococcus spp., Neisseria gonorrheae, anaerobes and Enterobacterieae. Mechanisms of tetracycline include tetracycline efflux, ribosome protection, and tetracycline modification. In contrast, tetracycline is used to treat acne and cholera, which are still susceptible to the antibiotic.

Image:bacteriacharacterizatione.jpeg


The bacteria grown here was then extracted to be used in PCR sequencing to identify the type of bacteria by its DNA sequence in an upcoming lab.

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