Global identification of genomic regions of difference in Bt strains. (a) BPGA hybridization patterns of natural Bt isolates compared to the BtE264 reference genome. Five Bt isolates are shown. Top row: chromosome (Chr) schematics of BtE264 Chr 1 and Chr 2. Green regions indicate previously identified genomic islands (GIs) , red regions indicate novel genomic islets (nGis) identified in this study. Lower rows: BGPA hybridization patterns for Bt strains. Only aCGH signals confined to the BtE264 section of the BGPA are depicted. Y-axis: log2 ratios of hybridization signals of each strain compared against BtE264. For all Bt strains except BtE264, regions of difference are identified by a log2 ratio dip or peak. Black arrows: representative GIs and nGis. The Bt exopolysaccharide (EPS) region in BtE555 is highlighted by a purple arrow. (b) Circular chromosomal graphs of recurrent regions of difference in Bt. aCGH results from 50 Bt isolates are depicted across BtE264 Chr 1 (left) and Chr 2 (right). Tracks are as follows, from outer to inner: first two tracks, Bt genes on forward and reverse strands (known genes (lime), mobile elements (black), hypothetical genes (pink)); blue, variable regions from aCGH data; green, previously described GIs; red, nGis identified in this study (red); brown, GC percentage of variable region compared to the Bt core genome. Grey dotted lines indicate 10% relative difference in GC content. Vertical grey line indicates the y-axis. The Bt EPS cluster is marked with a purple arrow.