In my first year of college, I began to do research in a microbiology laboratory. I stayed there until I come to the United States and participated in two projects. I have learned many things from this experience that are very important for my college carrier.
First project: Antagonist Acitivity of Shigella sonnei: Extraction, Purification and Characterization of Bacteriocins
Bacteriocins are antibacterial substances produced by a wide range of taxa, including Shigella. The genus includes four species, all agents of acute enteritis, extremely prevalent disease, especially in less developed regions. Bacteriocins contribute to the virulence of the bacteria, and it is plausible to assume that the synthesis of such substances explain the low infectious dose of the microorganism. Considering the importance of the subject and the lack of research in this topic, we have proposed the development of a project to study the production of bacteriocins by a sample of isolated S. sonnei from child with acute diarrhea.
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| Look how cool and beautiful they are! |
The test sample, previously known to express antagonism, was submitted to protein extraction and the precipitated intracellular extract (C75) was selected for subsequent stages of the project. First, we aim to determine the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of C75. The value of MIC and MBC was 200UA/mL. The equivalence of these values showed that C75 has bactericidal activity and this setting was an important step in the characterization of the substance.
Thereafter, C75 was purified by sequential chromatography steps and obtained active fractions were analyzed by mass spectrometer. The data obtained indicate that enable proteins were partially purified. Several proteins have been sequenced, and none of them had similar sequence already described. There was some identity between antagonist proteins and enzymes involved in carbohydrate metabolism, amino acid synthesis and in the quorum sensing process. Also sequences similar to unknown function proteins were obtained.
Our results suggest that the S. sonnei sample synthesizes bacteriocins not yet described or, alternatively, proteins already described which function as an antagonist substance has not been identified yet. The optimization of the purification protocol used is an essential step in the detailed characterization of the bacteriocins.
