Natural diversity of CRISPR spacers of Thermus: evidence of local spacer acquisition and global spacer exchange

We investigated the diversity of CRISPRspacers of Thermuscommunities from two locations in Italy, two in Chile and one location in Russia. Among the five sampling sites, a total of more than 7200 unique spacers belonging to different CRISPR-Cas systems types and subtypes were identified. Most of these spacers are not found in CRISPRarrays of sequenced Thermusstrains. Comparison of spacer sets revealed that samples within the same area (separated by few to hundreds of metres) have similar spacer sets, which appear to be largely stable at least over the course of several years. While at further distances (hundreds of kilometres and more) the similarity of spacer sets is decreased, there are still multiple common spacers in Thermuscommunities from different continents. The common spacers can be reconstructed in identical or similar CRISPRarrays, excluding their independent appearance and suggesting an extensive migration of thermophilic bacteria over long distances. Several new Thermusphages were isol...