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Erwinia amylovora CRISPR elements provide new tools for evaluating strain diversity and for microbial source tracking
Gayle C McGhee1, George W Sundin
1Department of Plant Pathology and Centers for Microbial Ecology and Pathogenesis, Michigan State University, East Lansing, Michigan, United States of America.
Plos One
|August 4, 2012
Summary
This study reveals significant genetic diversity in Erwinia amylovora using CRISPR array analysis. Spacer patterns differentiate strains, offering insights into bacterial evolution and host adaptation.
Area of Science:
- Bacteriology and Microbial Genetics
- Molecular Biology
- Plant Pathology
Background:
- Clustered regularly interspaced short palindromic repeats (CRISPR) and Cas proteins form an adaptive immune system in bacteria.
- CRISPR arrays exhibit variability in repeat and spacer content within bacterial genomes.
- Erwinia amylovora, a significant plant pathogen, presents an opportunity to study CRISPR-based genetic diversity.
Purpose of the Study:
- To investigate the genetic diversity of the plant pathogen Erwinia amylovora using comparative sequence analysis of CRISPR arrays.
- To uncover previously unknown variations in CRISPR array number and spacer content across geographically diverse strains.
- To correlate CRISPR genotypes with host range, plasmid content, and streptomycin resistance.
Main Methods:
- Comparative sequence analysis of CRISPR arrays from 85 Erwinia amylovora strains.
- Evaluation of CRISPR array number and spacer variability across strains from North America, Europe, New Zealand, and the Middle East.
- Identification and categorization of unique spacers and CRISPR array patterns.
Main Results:
- 588 unique spacers were identified across three CRISPR arrays, with 20, 17, and 2 pattern types respectively.
- Spacer content analysis differentiated Eastern U.S. apple/pear strains from Western U.S. strains.
- Strains from different hosts (Rubus, Indian hawthorn, loquat) showed distinct spacer profiles, and some North American strains shared genotypes globally.
- 16% of spacers targeted plasmids (55 targeting pEU30) and 5% targeted bacteriophages.
- Streptomycin-resistant strains in Michigan exhibited low diversity and matched sensitive strains.
Conclusions:
- CRISPR array analysis reveals substantial genetic diversity within Erwinia amylovora, influenced by geographic origin and host association.
- Spacer patterns serve as valuable markers for differentiating bacterial strains and understanding their evolutionary history.
- The findings provide insights into the adaptive potential of Erwinia amylovora and its interactions with plasmids and phages.
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