Clusted regularly interspaced palindromic repeats (CRISPRs) and their associated cas genes confer immunity to bacteria and archaea by incorporating segments of foreign DNA, known as spacers, into their chromosome to recognize and inactivate the invader in the future. Our research project aims to clone the CRISPR1 system from Streptococcus thermophilus strain LMD-9 and transform it into Escherichia coli and Bacillus subtilis. The design of our experiment was motivated by the increasing threat of antibiotic resistant bacterial populations to human health. By designing bacteria that have a fitness advantage from the CRISPR system, we could wipe out these dangerous bacteria under specific circumstances. The cas9 gene from S. thermophilus LMD-9 works as an endonuclease, in a manner similar to RNA interference, to recognize and cleave the antibiotic resistant plasmid from populations of bacteria using predesigned spacers, such as ones for kanamycin resistance.
Background
It has long been known that bacteria protect themselves against threats from bacteriophage attack through a variety of methods, apparent in the existence of restriction enzymes.
Streptococcus thermophilus is a lactic acid bacteria that is widely used as a starter culture for yogurt products in the United States. All sequenced strains of Streptococcus thermophilus are known to have at least one CRISPR locus, which work with varying degrees of success.
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