The Role Of Bacterial Defense Systems Against Viruses

1029 WordsMar 14, 20175 Pages
Organisms have evolved over time to become masters of survival . An example of this is bacteria, which have existed for nearly 3.5 billion years (1) and have evolved CRISPR/Cas as a mechanism of defense against exogenous sources such as bacteriophages . CRISPR (clustered randomly interspaced short palindromic repeats) was first discovered in 1993 by Francisco Mojica (2).The CRISPR locus contains spacers, motifs, and associated genes related to the locus to help with the destruction of target sequences. The application of these components in technology has the capacity to change science , as it allows for greater specificity and efficiency than other gene editing technologies such as TALEN (Transcription activator-like effector nucleases)…show more content…
Additionally, the investigators delved into spacer content relatedness to resistance. Investigators created variant loci and then tested them for resistance by deleting and adding spacers in the CRISPR locus. Results from this experiment suggested that spacers did not provide resistance to phages without specificity, as resistance was not necessarily increased when arbitrary spacers were added to the locus. Consequently, this led investigators to believe there were more factors involved in the CRISPR system, which led them to consider the effects of cas genes on resistance. Cas genes were previously thought to only be involved in DNA repair, however, they were also thought be involved in immunity. When cas-5 was inactivated, phage resistance was lost. This result lead to the overall result of the Barrangou paper, which was that the locus specificity for the target DNA of the phage, while cas genes provided as enzymatic machinery to provide immunity. After the foundations of the CRISPR locus were established by Barrangou, Jinek et al. investigated the specific process in which target DNA is cleaved in bacteria using the CRISPR/Cas system. Preceding Jinek’s study, the process of CRISPR-based immunity had been established, and different systems of CRISPR/cas had been disclosed. The focus of Jinek’s study was type II CRISPR, which process pre-crRNAs
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