Lateral gene transfer between the Bacteroidetes and Acidobacteria: the case of α-L-rhamnosidases

α-L-Rhamnosidases catalyze the hydrolysis of the terminal α-L-rhamnose residues in various carbohydrates. The catalytic domains in most of these enzymes belong to the families GH78 and GH106 of glycoside hydrolases. In this study, we show that almost all genes encoding the GH78- and GH106-containing proteins from members of the poorly characterized bacterial phylum Acidobacteria originated from precursors belonging to the phylum Bacteroidetes. Members of the Acidobacteria and Bacteroidetes display similar functional capabilities and specialize on degradation of plant-derived organic matter. Several proposed lateral gene transfers between the Acidobacteria and Bacteroidetes occurred presumably during specialization of these bacteria for their environments.