A complex gene locus enables xyloglucan utilization in the model saprophyte C ellvibrio japonicus.

The degradation of plant biomass by saprophytes is an ecologically important part of the global carbon cycle, which has also inspired a vast diversity of industrial enzyme applications. The xyloglucans ( XyGs) constitute a family of ubiquitous and abundant plant cell wall polysaccharides, yet the enzymology of XyG saccharification is poorly studied. Here, we present the identification and molecular characterization of a complex genetic locus that is required for xyloglucan utilization by the model saprophyte C ellvibrio japonicus. In harness, transcriptomics, reverse genetics, enzyme kinetics, and structural biology indicate that the encoded cohort of an α-xylosidase, a β-galactosidase, and an α- l-fucosidase is specifically adapted for efficient, concerted saccharification of dicot (fucogalacto)xyloglucan oligosaccharides following import into the periplasm via an associated TonB-dependent receptor. The data support a biological model of xyloglucan degradation by C . japonicus with striking similarities - and notable differences - to the complex polysaccharide utilization loci of the Bacteroidetes. [ABSTRACT FROM AUTHOR]