[Community structure and phylogenetic analysis of cyanobacteria in cryoconite from surface of the Glacier No. 1 in the Tianshan Mountains].

Objective: The purpose of this study is to characterize the community composition and phylogenetic analysis of cyanobacteria from supraglacial cryoconite of the Glacier No. 1 in the Tianshan Mountains, China.

Methods: We amplified 16S rRNA genes from the extracted cryoconite DNA by PCR with 2 pairs of cyanobacteria-specific primers. Amplificon was used to construct 16S rRNA genes clone library. The estimation of species richness, diversity indices, and rarefaction curve of the 16S rRNA genes library were determined based on representative phylotypes (OTUs).

Results: Analysis of 16S rRNA gene sequences allowed grouping of 101 clones into 12 phylotypes (OTUs) using a cut-off of 97% identity. The phylogenetic analysis revealed that most of sequences affiliated to the order Oscillatoriales and Chroococcales except that three were unclassified. The clone library was dominated by representatives of the order Oscillatoriales (81% of the total clones), and the most abundant organisms within this order were in the genus Phormidium (68 clones) including clones grouping into four phylotypes. The only clone of Chroococcales was closely related to the genus Chamaesiphon with 97% similarity. In addition, comparison of soil chemical properties between different habitats indicated that supraglacial cryoconite supported significantly higher the content of available phosphorus and potassium, nitrate nitrogen and organic matter compared with the forefield of the Glacier No. 1.

Conclusion: The diversity index of cyanobacteria were relatively high in supraglacial cryoconite of the Glacier No. 1 in the Tianshan Mountains. The community structure was dominated by members of the genus Phormidium. This study may enrich our knowledge on biogeochemical processes and ecological distribution of cyanobacterial populations in glacial ecosystem.