中央戈壁石下生物土壤结皮中细菌群落结构和多样性

Diversity and structure of hypolithic bacteria community of Zhongyang Gobi

摘要:

【背景】戈壁石下生物土壤结皮(Biological soil crusts，BSCs)中的微生物在干旱、半干旱地区生态系统物质循环中起重要作用，其细菌群落结构和多样性因气候和地理环境的不同而存在较大差异。中央戈壁面积大，其石下BSCs中细菌群落结构和多样性却知之甚少。【目的】比较中央戈壁石下BSCs和周围裸土中细菌群落结构和多样性的异同，揭示环境因子对它们的影响以及细菌之间的相互作用关系。【方法】利用Illumina MiSeq对16S rRNA基因进行高通量测序，使用生物信息学分析方法分析细菌群落结构和多样性及其影响因素；基于CoNet软件绘制物种共现性网络图，利用Cytoscape 3.5.1软件将网络图可视化。【结果】石下BSCs的速效磷(Available phosphorus，AP)、速效氮(Available nitrogen，AN)和叶绿素a (Chlorophyll a，Chl a)的含量均明显高于周围裸土(最高高出471%)，而pH则略低于周围裸土；石下BSCs中细菌的最优势菌门为Cyanobacteria (45.85%?53.77%)，优势属(9.25%?18.42%)有Trichocoleus、Chroococcidiopsis和属于Cyanobacteria纲的1个未知属；临近裸土中细菌的最优势菌门为Actinobacteria (38.82%?44.69%)，优势属(>5%)有Arthrobacter、Rubrobacter和其它3个属于放线菌门或酸杆菌门的未知属；在土壤理化因子中，AP对石下细菌群落组成的影响最大；除Actinophytocola属和Cyanobacteria纲中的未知属外，其他微生物之间均存在较强的互作关系，其中以共存的互作关系为主(约占60%)，点度中心性、接近中心性和中介中心性均较高的节点都属于Cyanobacteria门和α-Proteobacteria纲。【结论】中央戈壁石下BSCs中的细菌群落结构和多样性明显不同于临近裸土，Cyanobacteria门和α-Proteobacteria纲的细菌是该地区石下早期BSCs形成和发育最初及最重要的驱动力。

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.