胡杨叶片及韧皮部内生细菌多样性及生物学功能分析

Diversity and biological function of endophytic bacteria in Populus euphratica leaves and phloem

摘要:

【目的】通过分析胡杨叶片及树干内生细菌群落多样性、结构特征及生物学功能，探究内生细菌与宿主胡杨的互作机制。【方法】利用Illumina MiSeq高通量测序技术，对采集自新疆喀什地区胡杨林的3组胡杨树叶和3组树干样本的内生细菌进行Alpha、Beta多样性分析、群落组成分析以及通过比对代谢数据库进行群落功能预测，并对样品中内生细菌进行分离纯化鉴定。【结果】胡杨树叶优势菌群依次为变形菌门Proteobacteria（40.71%）、放线菌门Actinobacteria（21.76%）、拟杆菌门Bacteroidetes（14.24%）和厚壁菌门Firmicutes（13.92%）；胡杨树干优势菌群为厚壁菌门Firmicutes（56.91%）、放线菌门Actinobacteria（37.01%）。PCoA分析结果表明，胡杨树叶与树干的内生细菌群落结构存在明显差异，同类型组织样本群落结构相似。功能预测发现，内生细菌丰度较高的代谢通路及酶大多与细胞壁和细胞膜、外排泵、氧化应激、相容性溶质、能量代谢等相关。并分离到可培养内生细菌44株，分属5个属，其中芽孢杆菌属占比最多。【结论】胡杨叶片中内生细菌的多样性及丰富度均高于树干组织，不同胡杨组织由于生物学功能不同，也影响着内生细菌群落的组成。内生细菌群落的功能与宿主组织有对应关系，胡杨所处生境也影响着其内生细菌群落的功能表达。胡杨可培养内生细菌群落具有耐盐碱等特性，是具有应用潜力的菌种资源。

Abstract:

[Objective] To investigate the interaction mechanism between endophytic bacteria and host poplar, the diversity, structural characteristics and biological functions of the endophytic bacterial community in the leaves and trunk of Populus euphratica were analyzed.[Methods] By using Illumina MiSeq high-throughput sequencing technology, we performed Alpha and Beta diversity analysis, community composition analysis, and functional prediction compared with metabolic database of the endophytic bacteria on three groups of Populus euphratica leaves and three groups of trunk samples collected from poplar forests in Kashgar, Xinjiang, China. And endophytic bacteria from the samples were isolated and purified.[Results] The dominant groups of Populus euphratica leaves were Proteobacteria (40.71%), Actinobacteria (21.76%), Bacteroidetes (14.24%), and Firmicutes (13.92%), and the dominant groups of Populus euphratica trunk samples were Firmicutes (56.91%), Actinobacteria (37.01%). The results of PCoA analysis showed that there were significant differences in the endophytic bacterial community structure between Populus euphratica leaves and trunks, and the community structure of the same type of tissue samples was similar. Functional prediction revealed that the metabolic pathways and enzymes with higher abundance of endophytes were mostly related to cell wall and cell membrane, efflux pumps, oxidative stress, compatible solutes, energy metabolism, etc. A total of 44 cultivable endophytic bacteria belonging to five genera were isolated, among which Bacillus accounted for the largest proportion.[Conclusion] The diversity and abundance of endophytic bacteria in Populus euphratica leaves were higher than in trunk tissues, and different Populus euphratica tissues also influenced the composition of theendophytic bacterial community due to their different biological functions. The functions of the endophytic bacterial community corresponded to the host tissues, and the habitat in which Populus euphratica was located also influenced the functional expression of its endophytic bacterial community. The cultivable endophytic bacterial community of Populus euphratica has salt-tolerant and other characteristics, which are potential strain resources.