Secret of Bacteria's Immune System

Researchers from the University of Laval have unlocked the secret of bacteria’s immune system. CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats) is a mechanism that works by selecting foreign DNA segments and inserting them into very specific locations in a bacterium's genome. These segments then serve as a kind of immune factor in fighting off future invasions by cleaving incoming DNA. This mechanism was demonstrated using plasmids, the plasmid contained gene for antibiotic resistance, it was inserted into bacteria used in making yogurt (Streptococcus thermophiles). The bacteria integrated the segments of DNA from the resistance gene into their genome and the attempts to reinsert the plasmid into these bacteria failed showing that bacteria had been immunized against acquiring the resistance gene.
I find this interesting because it could help us understand why some bacteria develop antibiotic resistance while others don't.