Differentiation of the characteristics of excreted extracellular polysaccharides reveals the heterogeneous primary succession of induced biological soil crusts

In this study, the chemical composition and the macromolecular features of the extracellular polysaccharidic (EPS) matrix of induced biological soil crusts (IBSCs) of different age, collected in the hyper-arid plateau of Hobq desert, Inner Mongolia, China, were investigated. No statistically significant correlation between the amount of extracellular carbohydrates (i.e., monosaccharides, oligosaccharides, and polysaccharides) and the age of IBSCs was found. On the other hand, the relative abundance of uronic acid in the EPSs increased with the maturation of the crusts. In the EPSs of the investigated samples, glucose, mannose, galactose, and uronic acids were the sugars showing the widest variations in their relative abundance, explaining much of the variance of the data. Results also showed higher relative contents of EPSs with high MW in the oldest IBSCs. It is possible to conclude that the characteristics of the EPS of the matrix of the investigated IBSCs cannot only be put in relation with the age of the crusts and the activity of phototrophic microorganisms, but most properly, it has to be taken into account the biotic interactions ongoing between EPS producers and consumers.