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Addition of crystalline cellulose to semi-desert soil shifts the microbial population; this was assessed by following the 16S rRNA gene, glycosyl hydrolase, and measuring its functional diversity in the bacterial population. Quantification of the glycosyl hydrolase gene showed an increase from 1 x 10(4) g(-1) of unamended soil to 3 x 10(4) g(-1) of crystalline-cellulose-amended soil by the 15th day of crystalline cellulose utilization. The indigenous glycosyl hydrolase community in unamended soil was dominated by the clone families that were closely related to the glycosyl hydrolases from Betaproteobacteria and Firmi-cutes. The addition of crystalline cellulose induced a shift in the glycosyl hydrolase population toward an increase in the relative abundance of the glycosyl hydrolase that was consistent with those of Bacteroidetes and Flavobacteria. The population shift of glycosyl hydrolase was also supported by the comparison of the 16S rRNA gene families in unamended and crystalline-cellulose-amended soil libraries. The most abundant 16S rRNA gene sequences retrieved in the unamended soil were identical to Pseudomonas, Massilia, Paenibacillus, and Bacillus spp., while Cytopliaga and Flavobacterium spp. dominated in crystalline-cellulose-amended soil. (C) 2013 Elsevier Ltd. All rights reserved.