Article

Rapidly evolving CRISPRs implicated in acquired resistance of microorganisms to viruses

Department of Environmental Science, Policy and Management, University of California, Berkeley, Berkeley, CA 94720, USA.
Environmental Microbiology (Impact Factor: 6.24). 02/2008; 10(1):200-7. DOI: 10.1111/j.1462-2920.2007.01444.x
Source: PubMed

ABSTRACT Recent experimental evidence has demonstrated that bacteria acquire resistance to viruses by incorporation of short transcribed nucleotide sequences into regions of clustered regularly interspaced short palindromic repeats (CRISPR). We have analysed community genomic data from acidophilic microbial biofilms and discovered that evolution of the CRISPR regions in two distinct Leptospirillum group II bacteria occurs fast enough to promote individuality in otherwise nearly clonal populations. Comparative genomics strongly indicates very recent lateral transfer of the CRISPR locus between these populations, followed by significant loss of spacer sequences and locus expansion by unidirectional heterogeneous addition of new spacer sequences. Diversification of the CRISPR region is inferred to be a population-level response to the rapidly changing selective pressure of phage predation. Results reinforce the importance of phage-host interactions in shaping microbial ecology and evolution over very short time scales.

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    • "As an example, E. coli contains a CRISPR-Cas system that is efficiently silenced by H-NS [26], which could be interpreted as inactivation conferring a selective advantage. On the other side of the scale, in an analysis of acid mine drainage, extreme CRISPR diversity was observed where no two sampled individual cells had the same spacers [27]. The viruses in the acid mine drainage used recombination to diversify rapidly, making any but the most recent spacers lack a target [28]. "
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    Biochimie 04/2015; 437. DOI:10.1016/j.biochi.2015.03.025 · 3.12 Impact Factor
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    • "There are two primary characteristics of CRISPRs that make them suitable for such a purpose. First, due to the evolutionary arms race between foreign elements (e.g., phages) and the host bacteria, the associated rapidly changing selection pressures may cause CRISPRs to evolve quite quickly (Karginov & Hannon, 2010; Tyson & Banfield, 2008). Thus, through the acquisition of new and deletion of old spacers, differences useful for typing and subtyping (in Salmonella, this refers to strain identification and differentiation at the serovar and sub-serovar level) could arise even between closely related strains. "
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    PeerJ 04/2014; 2:e340. DOI:10.7717/peerj.340 · 2.10 Impact Factor
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    • "Given that this newly described bacterial defense system has been found in approximately half of all bacterial species studied, resistance mechanisms that target foreign genetic material in the cell may be less constrained than mechanisms targeting phage adsorption. Furthermore, these molecular defense mechanisms can now be productively studied using sequence-based technologies (Tyson & Banfield, 2008) to establish an idea of the relative importance of the different categories of bacterial resistance mechanisms. The prevalence of these mechanisms will undoubtedly shed light into bacteria–phage interactions in the environment. "
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