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

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.