Fig. 2

Scaffoldins and scaffoldin clusters of the Bacteroides cellulosolvens genome. a Schematic representation of the cohesin-borne scaffoldins. The 78 cohesins of B. cellulosolvens are classified into two main types: type I (33 modules) and type II (42 modules). In addition, group R was defined for cohesins from scaffoldins ScaR1-R3, whose sequences are notably different than those of the known types. We examined the conservation of the cohesin sequences within a given scaffoldin protein and among the different scaffoldins. Dots represent cohesin and dockerin modules that were selected, cloned, expressed, and examined experimentally. Clustered ORFs are enclosed by color-coded rectangles as defined in Fig. 1. Orange ellipses indicate scaffoldin ORFs that were fully expressed. Blue squares represent cohesins that were expressed in pairs/triplets. b Details of sca gene clusters. The figure represents the organization of the six sca gene clusters marked by letters A to F as designated in Fig. 1. Color-coding indicates the different ORFs within the specific cluster. The number in brackets within the regions indicates distances longer than 300 bp between the ORFs. Cluster A is a heterogeneous cluster including type I and type II cohesins where the scaffoldins possess only one cohesin. Cluster B includes ScaR3 located at a significant distance from the other two scaffoldins. The segment of 8-kb between ScaS and ScaR3 includes several ORFs of different function with relatively short distances (less than 300 bp) between them. Cluster C contains the two largest scaffoldins: ScaA1 is a primary scaffoldin that is bound by anchoring scaffoldin ScaB. The scaffoldins in Cluster D possess type II cohesins. ScaL1 and ScaL2 are very similar, except ScaL2 has an additional cohesin. The scaffoldins in Cluster E possess type I cohesins and together comprise the largest cluster with four scaffoldins. Cluster F is a heterogeneous cluster with two scaffoldins, each of which possesses a single cohesin and a single dockerin (see a)