Cobalamin biosynthesis pathway in Halobacterium NRC-1. (A) Cofactor and vitamin biosynthesis biomodules are linked to five genes of unknown function visualized in Cytoscape; (see Fig. 4 for key to network display). Genes implicated in cobalamin biosynthesis are shown in a larger font size. (B) mRNA changes for the cobalamin biosynthesis genes (the x- and y-axes are defined in Fig. 7). (C) Cobyrininc acid biosynthesis pathway. The proteins catalyzing the various steps are shown along with the standard correlation between mRNA changes in adjacent biochemical steps. The question mark (?) indicates enzymes yet to be identified. (D) Hierarchical clustering of mRNA changes using standard correlation. Red denotes up-regulation and green denotes down-regulation. The dendogram on the left represents closeness between two genes on the basis of the similarity in their expression level changes in the five perturbations.