Exploring Microbial Resource of Different Rhizocompartments of Dominant Plants Along the Salinity Gradient Around the Hypersaline Lake Ejinur

Abstract

Lake littoral zones can also be regarded as another extremely hypersaline environment due to hypersaline properties of salt lakes. In this study, high-throughput sequencing technique was used to analyze bacteria and fungi from different rhizocompartments (rhizosphere and endosphere) of four dominant plants along the salinity gradient in the littoral zones of Ejinur Salt Lake. The study found that microbial α-diversity did not increase with the decrease of salinity, indicating that salinity was not the main factor on the effect of microbial diversity. Distance-based redundancy analysis and regression analysis were used to further reveal the relationship between microorganisms from different rhizocompartments and plant species and soil physicochemical properties. Bacteria and fungi in the rhizosphere and endosphere were the most significantly affected by SO₄ ^2-, SOC, HCO₃ ^-, and SOC, respectively. Correlation network analysis revealed the potential role of microorganisms in different root compartments on the regulation of salt stress through synergistic and antagonistic interactions. LEfSe analysis further indicated that dominant microbial taxa in different rhizocompartments had a positive response to plants, such as Marinobacter, Palleronia, Arthrobacter, and Penicillium. This study was of great significance and practical value for understanding salt environments around salt lakes to excavate the potential microbial resources.

Keywords: extreme environments; rhizosphere soil microorganisms; root endophytic microorganisms; salt stress; soil properties.

FIGURE 1

Effects of rhizosphere soil and root endophytic samples on the community composition at the genus level of Bacteria and Fungi in the Ejinur Salt Lake. Genus with relative abundance less than 4% were defined as others. (A) Bacterial rhizospheric samples, (B) bacterial endophytic samples, (C) fungal rhizospheric samples, and (D) fungal endophytic samples. Salicornia europaea (A), Suaeda salsa (B), Phragmites communis (C), and Achnatherum splendens (D).

FIGURE 2

Ejinur Salt Lake different rhizosphere soil and root endophytic samples of microbial α-diversity. Different uppercase (Endophytic samples) and lowercase (Rhizospheric samples) letters indicate significant differences among plant species (p < 0.05). The abscissa letters indicate the plant species [S. europaea (A), S. salsa (B), P. communis (C), and A. splendens (D)].

FIGURE 3

The distance-based redundancy analysis (db-RDA) of these microbial community structure and environmental parameters. Numbers in parentheses in the axis labels was a percentage explanatory variable. (A) Bacterial rhizospheric samples, (B) bacterial endophytic samples, (C) fungal rhizospheric samples, and (D) fungal endophytic samples. S. europaea (A), S. salsa (B), P. communis (C), and A. splendens (D).

FIGURE 4

The differential phylogenetic distribution of bacteria (A,B) and fungi (C,D) in Ejinur Salt Lake different rhizosphere soil and root endophytic samples. The linear discriminant analysis scores of >4. The five rings of the cladogram stand for phylum (innermost), class, order, family, and genus. Different colored nodes represent microorganisms that play an important role in the grouping represented by color; yellow represents non-significant. Uppercase “G” represents the rhizospheric sample, and uppercase “R” represents the endophytic samples. S. europaea (A), S. salsa (B), P. communis (C), and A. splendens (D).

FIGURE 5

An overview of the bacterial network interactions in Ejinur Salt Lake different rhizosphere soil and root endophytic samples. The connections in the network represent a strong (| r| > 0.6) and significant (p < 0.01) correlation. Colors of nodes represent different major phyla; the node representing genus is written inside. A green link indicates a negative interaction, whereas a red link implies a positive interaction between two individual nodes. Uppercase “G” represents the rhizospheric sample, and lowercase “R” represents the endophytic samples. (A–D) S. europaea rhizosphere soil (GA), S. salsa rhizosphere soil (GB), P. communis rhizosphere soil (GC) and A. splendens rhizosphere soil (GD). (E–H) Salicornia europaea endophytic samples (RA), Suaeda salsa endophytic samples (RB), Phragmites communis endophytic samples (RC) and Achnatherum splendens endophytic samples (RD).