Microbes that have evolved to live on lignocellulosic biomass face unique challenges in the effective and efficient use of this material as food. The bacteriumShewanellasp. ANA-3 has the potential to utilize arabinan and arabinoxylan, and uptake of the monosaccharide,l-arabinose, derived from these polymers, is known to be mediated by a single ABC transporter. We demonstrate that the substrate binding protein of this system, GafASw, binds specifically tol-arabinofuranose, which is the rare furanose form ofl-arabinose found in lignocellulosic biomass. The structure of GafASwwas resolved to 1.7 Å and comparison toEscherichia coliYtfQ (GafAEc) revealed binding site adaptations that confer specificity for furanose over pyranose forms of monosaccharides, while selecting arabinose over another related monosaccharide, galactose. The discovery of a bacterium with a natural predilection for a sugar found abundantly in certain lignocellulosic materials suggests an intimate connection in the enzymatic release and uptake of the sugar, perhaps to prevent other microbes scavenging this nutrient before it mutarotates tol-arabinopyranose. This biological discovery also provides a clear route to engineer more efficient utilization of plant biomass components in industrial biotechnology.