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What is antibiotic resistance?

If you’ve ever gone to the doctor for an ear ache, sinus infection, strep throat, or acne, you’ve probably been prescribed an antibiotic. Antibiotics fight bacteria by either stopping them from reproducing or destroying them. For example, the common antibiotic penicillin works by keeping a bacterium from building a cell wall. However, over usage of antibiotics have contributed to bacteria mutating, thereby becoming resistant to conventional antibiotics. As those bacteria go on to reproduce, in no time does a strain of bacteria become resistant to drugs.

What is CRISPR-CAS9 system?

Discovered in 2012 at UC Berkely, CRISPR-CAS9 is the most powerful gene editing tool to date. When a bacterium is under attack by virus, the immune system of the bacteria grabs viral RNA and “tucks” the sequence into CRISPR-short for “clustered regularly interspaced short palindromic repeats” located in the viruses genome. The next time the virus attacks the bacterium is prepared: using the appropriate CRISPR sequence in the genome, a guide RNA (gRNA) is synthesized that directs a protein, Cas 9, to the viral DNA. Acting as molecular scissors, the Cas-gRNA complex binds to the viral DNA and dices up the genetic material.

Why does CRISPR-CAS9 matter?

An application of CRISPR-CAS9 is that of treating drug resistant infections. CRISPR-CAS9 should be able to cut out the resistant gene in an antibiotic resistant bacterium, thereby making the bacteria susceptible to antibiotics. However, for CAS9 to be effective, it has to get to that bacterium. We hope to use signal peptides and protein fusions to lead Cas9 and a guiding gRNA into an OMVs. OMVs are naturally occurring extracellular vesicles that are used for cross talk between bacteria. Hence, they make strong candidates for transportation of Cas9/gRNA to the site of infection.