|The CRISPR-Cas system has been found to play roles|
in the antibiotic resistance of some bacteria. <Source>
In recent years, CRISPRs (Clustered, regularly interspaced, short palindromic repeats) have been gaining popularity in the microbiology field. Briefly, CRISPRs serve as an adaptive immune system for bacteria, meaning that they are able to remember what viruses (bacteriophages) or other entities have infected them and mount a targeted defensive response the next time they are infected with the same entity (think of it as an analog to our adaptive immune response which uses antibodies and other agents to target invading microbes). More specifically, the CRISPR-Cas (Cas are the CRISPR associated genes) system facilitates the integration of a small section of the foreign genomic DNA into the CRISPR array within the bacterial genome (see left side of the detailed diagram below). While in the array, this section of foreign DNA will serve as a template for recognizing the invading genome again if another infection occurs, and the template will be used for targeting that invading genome for rapid destruction. As can be seen in the figure below, this system is similar to the Eukaryotic RNA-interference system found in organisms including humans. I've already gotten pretty technical here, and anything more in-depth would be beyond the scope of this post, so please check out reference  for further reading.