Abstract: Biological soil crusts，given their extraordinary abilities to survive desiccation and extreme high temperatures，high pH and high salinity，have been found in deserts all over the world．They play a significant role in the process of formation，stability and fertility of soil，prevention of soil erosion caused by wind or water. Comparing to other biological soil crusts （algae crust or lichen crusts），moss crusts play the most significant role in ensuring the proper functioning of desert ecosystem，such as involvement in the process of formation，stability and fertility of soil，prevention of soil erosion caused by wind or water. Our previous research found that the quantity of microbe in the moss crusts was high. However，we had no idea with the diversity of those microbes when we wanted to use them in the sand-fixing application. In order to investigate the relationship between the moss and the microbe around the rhizoid，25 bacterial strains were isolated from moss crusts using three different medium. Phylogenetic analysis of partial 16S rDNA sequences showed as follows：（1） These strains were clustered into 3 phyla，3 classes，4 orders，6 families and 6 genera via Ribosomal Database Project （RDP） classifier. The phyla Proteobacteria，Actinobacteria and Firmicutes respectively owned 2，8，15 of the 25 strains. The dominant genera were Bacillus（52%） and Streptomyces （24%）. （2） Further classification of these strains was achieved via Basic Local Alignment Search Tool （BLAST） Homology analysis of the partial 16S rDNA against the EzTaxon-e database. BLAST results yielded 18 Operational Taxonomic Units （OTUs） and no novel species whose sequence similarity was lower than 97% compare to the species in the EzTaxon-e database. Most of these OTUs belong to the genus Bacillus （39%） and Streptomyces（33%）. （3） The Shannon-Wiener diversity index of moss crusts was 2.77，the value higher than that of lichen crusts for the same Gurbantunggut Desert. Because that the sand-fixing and water-trapping ability of moss crusts was stronger than that of lichen which would provide suitable habit for more microbe. For example，the leaf hair points of moss were confirmed as a critical part of adaptation to，and survival in，the extremely arid environment of the Gurbantunggut Desert，facilitating the capture of minimal quantities of water （rain，fog and/or dew），increasing the speed at which water could be absorbed into the leaf，and altering the leaf angle to effect optimum photosynthesis and carbon gain. We should pay more attention to the silicate bacterium such as Paenibacillus mucilaginosus which existed in both lichen crusts and moss crusts. It should be note that silicate bacterium could release lots of nutritional ions from soil and exhibited a multifunctional role for sand stabilization and maintenance of water. Although no nitrogen-fixing bacteria strains such as Azotobacter were isolated in this research，our unpublished data based on 454 sequencing techniques showed that the species belong to Rhizobiales was abundant. The complicated mutualistic symbiosis relationship between moss and bacteria in moss crusts would improve the development and ecological function of BSCs.

Key words: prokaryote, Ribosomal Database Project （RDP） classifier, EzTaxon-e database, Shannon-Wiener diversity index, silicate bacterium