Sequence analysis of CRISPR arrays of Erwinia amylovora isolates from Canada.

Yagubi, A.I., Castle, A.J., and Svircev, A.M. (2014). "Sequence analysis of CRISPR arrays of Erwinia amylovora isolates from Canada.", Acta Horticulturae (ISHS), 1056, pp. 149-153.

Abstract

CRISPRs (Clustered Regularly Interspaced Short Palindromic Repeats) are novel aspects of bacterial defense systems that allow bacterial hosts to acquire resistance or immunity against bacteriophages and plasmids. Bacterial CRISPRs are sites containing conserved short direct repeats separated by sequences termed "spacers". The spacers may match sequences in bacteriophage genomes and/or plasmids. Spacers are utilized by the CRISPR system to recognize and silence invading bacteriophages and other exogenous genetic elements. In the present study, we have determined, whenever possible, the DNA sequence of CRISPR arrays of selected Erwinia amylovora isolates from different geographic regions in Canada, and the existence of bacteriophage sequences as spacers was explored. About 92% of spacers show no significant homology to bacteriophages and plasmids sequences in NCBI database. No spacers matched the sequences of any sequenced E. amylovora bacteriophages from the Myoviridae and Podoviridae families. The ability of E. amylovora to gain new spacers in CRISPR arrays after bacteriophage infection was examined. Twenty-five bacteriophage insensitive mutants were recovered after infection and were examined to determine if their resistance to bacteriophages was due to spacers' acquisition. No changes (insertion or deletion) were detected in the CRISPR arrays of these isolates suggesting that these mutants became resistant to bacteriophages as a result of an unidentified resistance mechanism not based on the CRISPR system.

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