Abstract: Cyanobacteria, an important component of biological soil crusts in desert, exhibit low representation if studied using 16S rRNA amplicons with bacterial universal primers. The effectiveness of cyanobacteria 16S rRNA-specific primers has been verified by clone library studies, but appropriate species annotation methods for the study of amplicon by using this special primer are lacking. We conducted amplification comparison between the two primers, and compared cyanobacteria species annotation in different databases to establish species annotation and analysis process of desert cyanobacteria 16S rRNA amplicons. Combined with soil physicochemical properties, the diversity, community structure and environmental driving factors of cyanobacteria in algal crust soils in three regions of Gurbantunggut Desert were studied. The results showed that the cyanobacteria-specific primers could amplify desert cyanobacteria specifically, and that the cyanobacteria sequence accounted for 90.54%. The representative sequences of Operational Taxonomic Units (OTUs) obtained by the amplification had the optimal annotation effect when compared with Kraken2 standard library. The results showed that 4 orders, 13 families and 19 genera of cyanobacteria were obtained, and the dominant genera were Oscillatoria and Microcoleus. There was no significant difference in the α and β diversity, as well as abundance, of cyanobacterial communities in soil crust across different regions. The community structure was uniform, without obvious differentiation. Soil physicochemical factors, such as total nitrogen, ammonium nitrogen and nitrate nitrogen of algal crust, were significantly different in different regions of the desert (P<0.05). Results of Mantel test and correlation analysis showed that ammonium nitrogen content in crust soil was significantly correlated with the community structure of cyanobacteria (P<0.01). There was a significant positive correlation between Oscillatoria and microbial nitrogen, and a significant negative correlation between Microcoleus and nitrate nitrogen. These results could provide a better annotation and analysis process for the study of 16S rRNA amplicon of desert cyanobacteria, and provide a scientific basis for examining the community structure, species diversity and environmental driving factors of cyanobacteria.

Key words: Gurbantunggut Desert, algal crusts, cyanobacteria, high-throughput sequencing, biodiversity