Potential complementary functions among bacteria, fungi, and archaea involved in carbon cycle during reversal of desertification

Development of biological soil crusts (BSCs) on bare land is a sign of reversal of desertification, and microbial communities of BSCs are the biogeochemical engineers of desert ecosystems. However, regulation of different microbial groups involved in the carbon (C) cycle is not clear. This study investigated the correlation between bacteria, fungi, and archaea of BSCs involved in the C cycle during reversal of desertification through community abundance analysis by quantitative PCR and functional gene detection using GeoChip 5.0. Among the known C cycle genes found in BSCs, 84.5% of C degradation genes, 95% of C fixation genes, and all of methane oxidation genes were derived from bacteria owing to their highest proportion among the total microbial abundance of BSCs; some recalcitrant C degradation genes were derived from fungi; and other C fixation pathway and methanogenesis genes originated from archaea. The increased abundance of bacteria and fungi and decreased abundance of archaea during reversal of desertification, as well as the difference in C cycle genes of the three microbial groups, indicated the functional complementarity among these microorganisms involved in C cycle. At the early stage of BSC development, archaea, and bacteria provide available C sources by autotrophic CO2 fixation pathway; bacteria play important roles in C degradation, C fixation, and methane oxidation during the entire BSC development process; and fungi mainly degrade lignin at the later stage of BSC development. Thus, cooperation among BSC microflora altered C cycle during reversal of desertification.