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The CRISPR-Cas (clustered regularly interspaced short palindromic repeats-CRISPR-associated proteins) modules are adaptive immunity systems that are present in many archaea and bacteria. These defence systems are encoded by operons that have an extraordinarily diverse architecture and a high rate of evolution for both the cas genes and the unique spacer(More)
The evolution of CRISPR-cas loci, which encode adaptive immune systems in archaea and bacteria, involves rapid changes, in particular numerous rearrangements of the locus architecture and horizontal transfer of complete loci or individual modules. These dynamics complicate straightforward phylogenetic classification, but here we present an approach(More)
Clustered regularly interspaced short palindromic repeats (CRISPR) and their associated CRISPR-associated sequence (CAS) proteins constitute a novel antiviral defence system that is widespread in prokaryotes. Repeats are separated by spacers, some of them homologous to sequences in mobile genetic elements. Although the whole process involved remains(More)
Prokaryotes contain short DNA repeats known as CRISPR, recognizable by the regular spacing existing between the recurring units. They represent the most widely distributed family of repeats among prokaryotic genomes, suggesting a biological function. The origin of the intervening sequences, at present unknown, could provide clues about their biological(More)
We report here the effect of environmental parameters, salinity, temperature, and an intercalating drug on plasmid topology in the halophilic archaeon Haloferax volcanii. We first studied the topological state of the plasmid pHV11 in media of different salt compositions and concentrations. The superhelical density of plasmid PHV11 varies in a way that(More)
Haloferax volcanii and Halomonas elongata have been selected as representatives of halophilic Archaea and Bacteria, respectively, to analyze the responses to various osmolarities at the protein synthesis level. We have identified a set of high-salt-related proteins (39, 24, 20, and 15.5 kDa in H. elongata; 70, 68, 48, and 16 kDa in H. volcanii) whose(More)
To identify genomic regions involved in osmoregulation in the extremely halophilic archaeon Haloferax volcanii, we used a technique which involves hybridization of cDNAs obtained at different salinities against a cosmid library of the organism. Both low and high salt concentrations trigger differential expression; however, adaptation to low salinities seems(More)
Prokaryotes immunize themselves against transmissible genetic elements by the integration (acquisition) in clustered regularly interspaced short palindromic repeats (CRISPR) loci of spacers homologous to invader nucleic acids, defined as protospacers. Following acquisition, mono-spacer CRISPR RNAs (termed crRNAs) guide CRISPR-associated (Cas) proteins to(More)
BACKGROUND Ileal lesions of Crohn's disease (CD) patients are abnormally colonized by pathogenic adherent-invasive Escherichia coli (AIEC) able to invade and to replicate within intestinal epithelial cells and macrophages. PRINCIPAL FINDINGS We report here the complete genome sequence of E. coli LF82, the reference strain of adherent-invasive E. coli(More)