Structure and Function of Soil Bacterial Communities in the Different Wetland Types of the Liaohe Estuary Wetland

Abstract

Soil bacterial communities play a crucial role in the functioning of estuarine wetlands. Investigating the structure and function of these communities across various wetland types, along with the key factors influencing them, is essential for understanding the relationship between bacteria and wetland ecosystems. The Liaohe Estuary Wetland formed this study's research area, and soil samples from four distinct wetland types were utilized: suaeda wetlands, reed wetlands, pond returning wetlands, and tidal flat wetlands. The structure and function of the soil bacterial communities were examined using Illumina MiSeq high-throughput sequencing technology in conjunction with the PICRUSt analysis method. The results indicate that different wetland types significantly affect the physical and chemical properties of soil, as well as the structure and function of bacterial communities. The abundance and diversity of soil bacterial communities were highest in the suaeda wetland and lowest in the tidal flat wetland. The dominant bacterial phyla identified were Proteobacteria and Bacteroidota. Furthermore, the dominant bacterial genera identified included RSA9, SZUA_442, and SP4260. The primary functional pathways associated with the bacterial communities involved the biosynthesis of valine, leucine, and isoleucine, as well as lipoic acid metabolism, which are crucial for the carbon and nitrogen cycles. This study enhances our understanding of the mutual feedback between river estuary wetland ecosystems and environmental changes, providing a theoretical foundation for the protection and management of wetlands.

Keywords: bacterial community; bacterial diversity; estuary wetland; functional genes.

Figure 1

Soil physicochemical properties in different wetland types. Data are presented as mean values ± standard error (n = 3). Different letters (a, b, c) within the same row indicate significant differences; p < 0.05.

Figure 2

The effective sequence information detected in the various wetland types, the number of OTUs at the phylum level, Chao1 index, and Shannon index (a), with data shown as mean values ± standard error (n = 3). Different letters (a, b, c) within the same row indicate significant differences at p < 0.05. A Venn diagram of soil bacterial OTUs is depicted in (b). The non-metric multidimensional scaling analysis (NMDS) is illustrated in (c). The redundancy analysis (RDA) of the soil bacterial communities with respect to the soil physicochemical properties is shown in (d).

Figure 3

Abundance of dominant bacterial genera (a) and phyla (b) in the soil of different wetland types.

Figure 4

LEfSe analysis reveals significant variations in bacterial taxa between different wetland types. It presents a cladogram illustrating these differences in soil bacterial abundance across the various wetland types. In the evolutionary branch diagram, the circular radiation emanating from the center represents the taxonomic ranks of phyla and genera, and each small circle indicates the position of a taxonomic rank within different classification levels, with the circle diameter proportional to the relative abundance. Species exhibiting no significant differences are uniformly colored yellow, while others are colored according to their highest abundance.

Figure 5

The LDA effect size bar plots illustrate differentially abundant bacterial taxa in the wetlands of the Liaohe Estuary. These plots present the LEfSe analysis LDA bar chart, where the vertical axis denotes the taxonomic units that are significantly different between groups, while the horizontal axis visualizes the logarithmic scores from the LDA difference analysis corresponding to each classification group. The data are sorted by score magnitude to convey the differences observed. The length of each bar represents the extent of the difference between the grouped samples; thus, a longer bar indicates a more significant difference between the taxonomic units. Additionally, the varying colors in the bar chart correspond to the sample groups in which each taxonomic unit is more abundant.

Figure 6

Primary and secondary metabolic functions of soil bacterial communities.

Figure 7

Tertiary metabolic functions of soil bacterial communities. The bar graph illustrates the relative abundances of major metabolic functions within soil bacterial communities across various wetland types. Different letters (a, b) in the same row signify significant differences at p < 0.05.