Reconstruction of the xylose and xyloside utilization pathway in Firmicutes. Functional roles present in C. acetobutylicum and B. subtilis are shown on green and yellow backgrounds, respectively. Those present in other bacteria of the same lineage (but not in C. acetobutylicum and B. subtilis) are shown on a gray background. Tentatively predicted functional roles are marked by asterisks. Solid arrows denote enzymatic reactions and transport, and broken arrows denote links to other catabolic pathways (utilization of arabinose and xylitol) that are not analyzed in this study.