Genotyping probiotic Bifidobacterium longum strains using CRISPR loci

Abstract

Bifidobacterium longum strains are amongst the most widely used probiotics for human consumption due to their ability to modulate the host immune response, and withstand passage through the human gastrointestinal tract. Clustered Regularly Interspaced Short Palindromic Repeats, CRISPR, occur widely in bacteria and provide adaptive immunity via acquisition of DNA sequences from viruses and plasmids that constitute unique genetic records of immunization in each bacterium (1). CRISPR-Cas systems comprise a variety of cas genes and a repeat-spacer array, where the repeat sequence (diamonds) flanked the spacers (squares). The spacers are short sequences homologous to the invasive DNA that the bacteria recorded to be immunize against a future challenge with the same virus. Spacers represent the immune background of each strain and are consider a barcode for genotyping each strain