CRISPR-CasSYSTEMS IN ENTEROCOCCAL STRAINS OF DAIRY ORIGIN

BONACINA, J.; LECHNER, M; RODRIGUEZ, V; FADDA S,; SAAVEDRA, L.

Buenos Aires

Congreso; Reunión Conjunta de Sociedades de Biociencias (SAIB); 2017

SAIB

The CRISPR-Cas modules are adaptive immune systems thatrestrict the acquisition of foreign mobile elements. They can be found in many bacteria and most archaea, and consistof a CRISPR array, comprising conserved short direct repeats (DR) separated by short variable DNA sequences (spacers), preceded by a 5'-leader sequence; andof casgenes that encode proteins performing various, only partially characterized functions essential for the system?s activity. Particularlyspacers, represent remnants of genetic code from past invaders (protospacers) andwork as guides to specifically target and cleave the nucleic acids of cognate viruses or plasmids.Based on the evidence indicating that enterococci possessing one or more complete CRISPR-Cas cassettes are less parasitized by phage and other mobile elements, which include antibiotic resistance genes, the presence ofthese immune systems in the genomes of 14 enterococcal strainsisolated from milk or dairy productswas evaluated.For this purpose,the CRISPRFinder webserverwas used. As a result, it was observed that 7 strains, belonging to 4 different species, included at least one CRISPR array with three motifs (DR + spacer) and a minimum of two identical DRs; and that almost all strainshad 1 or more spacers, with the exception ofEnterococcus (E.) mundtii CRL1656 and ATCC 882 with noCRISPR.Then, in order to identify and label spacers origin, the CRISPRTarget program was run settingGenbank-Phage and Ref-Seq-Plasmid as databases. Thus, from a total of 64 spacers that were present in both confirmed and questionable CRISPR, only 12protospacerscould be identified with a final score ≥ 25and 1 or no mismatches.Of these, 9, from a same or different strains, occur in a region codifying a replication protein RepA of several E. faecium and E. hirae plasmids. All in all, the evaluation of the potential of food related strains to acquire foreign DNA that may encode unwanted features is important in terms of food safety.Keywords: Enterococcus, dairy origin, CRISPR-Cas system, spacers