Expression of P . abyssi CRISPR cassettes. (A) Genomic locations of P. abyssi CRISPR loci. CRISPR cassettes and CRISPR-related operons encoding cas and cmr genes mapped on the circular P. abyssi chromosome. Orientations of CRISPR cassettes and adjacent genes are denoted. Depicted gene coordinates are based on the available completed genome of P. abyssi GE5. Direct repeats and degenerate direct repeats are indicated by black and grey boxes, respectively. Promoters upstream of CRISPR cassettes are denoted by arrows. Cr1-1, Cr4-1 and Cr4-12-RNAs are indicated in red. (B) Stable transcripts detected by Northern blot from CRISPR 1 and CRISPR 4 in exponential growth phase (E), entry into stationary phase (ES) or stationary phase (S). Arrows on the right indicate discrete RNA transcripts. The 5' end-labeled digest of Φx174 DNA with HinfI served as length nucleotide marker (M). The box C/D guide RNA, sR26, served as a loading control (bottom panel). (C) Detailed features of the CRISPR leader sequences drawn to scale with the direct repeat sequence of the two CRISPR families. Positions are relative to the transcription start (+1) of the CRIPSR precursor (preCr) indicated by a red arrow. The palindromic sequences in the direct repeat (DR) are represented by two inverted arrows. The 5' end of CR1-1 is indicated by a red arrow in the DR1 sequence. The -10 and +30 boxes indicate BRE/TATA promoter sequences and a conserved 5 nt poly A sequence, respectively.