Induction effect of exogenous cellulose on bacterial community of microbial soil crust

Abstract:

[Objective] Microbial soil crusts (MSCs) play an important role in the restoration of the ecological environment and the containment of soil desertification. The microbes in MSCs, especially the cellulose degrading bacteria (CDB), can stablize and repair the related ecological environment. The induction of exogenous cellulose is a major pathway for the full acknowledgment in the CDB’s diversity and their contribution to MSCs’ development. [Methods] Two cellulose materials (crushed wheat straw and sawdust) were added into MSCs separately, to determine the variation of the bacterial community induced by the exogenous cellulose based on PCR-DGGE. [Results] The exogenous cellulose especially wheat straw, rapidly increased the diversity and richness of bacterial community by approximately 66.7% and 15.8%, respectively. Samples subjected to the same treatment well grouped in together in cluster analysis based on DGGE bands profiles, suggesting that cellulose has a crucial effect on the bacterial community. The exogenous cellulose induced a remarkable variation of the structure of the bacterial community, of which the most variable was caused by wheat straw. Firmieutes and Alphaproteobacteria groups were always the predominant group in all samples. Among the obtained sequences, 13 bands were closely and phylogeneticly related to CDB and therefore they may be sourced from CDB. The anaerobic Clostridium group predominated these possible CDB (accounted for 46.1%), followed by Bacillus (30%). The exogenous cellulose degradation also induced the increase of the abundance or richness of some specific bacteria, like Microcoleus vaginatus and some Alphaproteobacteria groups, which had a significant function in MSCs development with the abilities in secreting polysaccharides to enhance the cohesion of soil particles or fixing carbon and/or nitrogen to improve the soil nutrition level. [Conclusion] Results provided a basis for the appreciation of the CDB diversity and the variation of the bacterial community structure induced by exogenous cellulose, and meanwhile lent theory evidence for the practical pathway in desert ecosystem restoration.

Key words:cellulose-degrading microbe, diversity, PCR-DGGE, wheat straw, wood chips