Diversity and structure of hypolithic bacteria community of Zhongyang Gobi

Abstract:

[Background] Bacteria of hypolithic biological soil crusts (BSCs) in Gobi play an important role in the biogenic elements circling in arid and semi-arid regions. The bacterial community structure and diversity vary greatly due to different climatic and geographical environments. The area of Zhongyang Gobi is large, but little is known so far about the structure and diversity of the hypolithic bacteria community. [Objective] To compared and analyzed the similarities and differences of bacterial community structure and diversity in hypolithic BSCs and bare soil around in the Zhongyang Gobi, and discover the effect of environmental factors on bacterial community and the interaction relationships among the bacteria. [Methods] Illumina MiSeq was applied to sequence 16S rRNA gene, bioinformatics approach was used to reveal the diversity and structure of the bacteria community, the co-occurrence network was constructed based on CoNet software and Cytoscape 3.5.1 to visualize the network. [Results] The contents of available phosphorus (AP), available nitrogen (AN) and chlorophyll a (Chl a) of the soil were significantly higher (the most of 471% higher), while pH were slightly lower in the BSCs than that in the bare soil. The bacteria was mostly dominated by the phylum of Cyanobacteria (45.85%?53.77%) and by the genera Trichocoleus, Chroococcidiopsis and unknown one belonged to Class Cyanobacteria (9.25%?18.42%) in the hypolithic BSCs, and did by the phylum of Actinobacteria (38.82%?44.69%) and by the genera Arthobacter, Rubrobacter and three unknown genera belonged to the phylum of Actinobacteria or Acidobacteria (>5%) in the adjacent bare soil. Among all the soil physicochemical factors, AP had the most significantey influence on the composition of hypolithic bacterial communities. Except the genera of Actognophytocola and one unclassified of Class Cyanobacteria, there were strong interaction existed among other phylotypes, in which the co-occurrence relationship was dominant (about 60%) and the nodes were all belonged to Phylum Cyanobacteria and Class α-Proteobacteria with higher degree, closeness and betweenness centralities. [Conclusion] Bacterial diversity and community structure of hypolithic BSCs is remarkably distinguished from that of bare soil in the Zhongyang Gobi. Members of Phylum Cyanobacteria and Class α-Proteobacteria are the primary and most important driver in the early development of hypolithic BSCs in the Zhongyang Gobi.

Key words:Hypoliths, 16S rRNA gene, High-throughput sequencing, Co-occurrence network