The bacterial community structure and function of Suaeda salsa rhizosphere soil

Suaeda salsa is an ideal agent for the biological enrichment of saline-alkali soil. Microorganisms in the rhizosphere of this plant play an essential role in soil improvement. The Illumina Misep high-throughput sequencing platform was used to explore the structural composition and function of the bacterial community in the rhizosphere soil of S. salsa and bare soil from coastal saline-alkali land in the Bohai Bay Rim area of Hebei, Shandong, and Tianjin, China. In total, 734 792 effective sequences were obtained from 16 samples, of which 4 285 OUTs belonged to 41 phyla, 100 classes, 282 orders, 400 families, 892 genera, and 1 577 species. The bacterial community in the rhizosphere soil of S. salsa contained Proteobacteria, Actinobacteria, Chloroflexi, Bacteroidetes, Gemmatimonadetes, Acidobacteria, Firmicutes, Cyanobacteria, Patescibacteria, and Planctomycetes. These results were consistent with the Alpha diversity analysis results, indicating that the community was highly diversified and significantly different from that of the bare soil. The LEfSe (LDA Effect Size) analysis showed that indicator species differentially occurred in S. salsa and bare soils. In S. salsa soil, Cyanobacteria, Acidobacteria, Alphaproteobacteria, Oxyphotobacteria, Chloroflexi, Rhizobiales, Nostocales, Sphingomonadales, Sphingomonadaceae, and Bacillus were the indicator species. Based on principal coordinates analyses and a correlation heatmap, the main factors affecting the soil bacterial community at order level were the presence of S. salsa, alkali-hydrolyzable nitrogen, available potassium, available phosphorus, and electrical conductivity. Also, Ectothiorhodospira and Balneolaceae could survive in bare soil with poor fertility, high salinity, and a viscous structure. PICRUSt (Phylogenetic Investigation of Communities by Reconstruction of Unobserved States) analysis showed that 304 metabolic pathways at pathway level 3 were active in both soil, of which 41 pathways, especially those involving in metabolism were different between S. salsa soil and bare land soil. These results indicated that S. salsa growth has a positive effect on the diversity and function of soil bacterial community by improving soil structure and increasing nutrients levels. These findings may be applied to improve saline-alkali land, optimize soil environment, and enhance its usefulness and sustainability.