Heterogeneity of interactions of microbial communities in regions of Taihu Lake with different nutrient loadings: A network analysis

Xinyi Cao,Rui Huang,Huimin Xu,Dayong Zhao,Zhongbo Yu,Jin Zeng

doi:10.1038/s41598-018-27172-z

Abstract

To investigate the differences in the interactions of microbial communities in two regions in Taihu Lake with different nutrient loadings [Meiliang Bay (MLB) and Xukou Bay (XKB)], water samples were collected and both intra- and inter-kingdom microbial community interactions were examined with network analysis. It is demonstrated that all of the bacterioplankton, microeukaryotes and inter-kingdom communities networks in Taihu Lake were non-random. For the networks of bacterioplankton and inter-kingdom community in XKB, higher clustering coefficient and average degree but lower average path length indexes were observed, indicating the nodes in XKB were more clustered and closely connected with plenty edges than those of MLB. The bacterioplankton and inter-kingdom networks were considerably larger and more complex with more module hubs and connectors in XKB compared with those of MLB, whereas the microeukaryotes networks were comparable and had no module hubs or connectors in the two lake zones. The phyla of Acidobacteria, Cyanobacteria and Planctomycetes maintained greater cooperation with other phyla in XKB, rather than competition. The relationships between microbial communities and environmental factors in MLB were weaker. Compared with the microbial community networks of XKB, less modules in networks of MLB were significantly correlated with total phosphorous and total nitrogen.

Highlights

Microorganisms are crucial components of aquatic ecosystems, and play important roles in the ecological processes in freshwater lakes[1,2]
Comparison of various indexes of the resulting network, including modularity (MD), clustering coefficient (CC), average path length (APL), and network diameter (ND), to those of random networks using Z-tests indicated that the bacterioplankton, microeukaryotes and the inter-kingdom networks in the two regions were non-random (P < 0.001) (Table 1)
The results of the present study demonstrated that the network structure and co-occurrence patterns were significantly different between the Meiliang Bay (MLB) and Xukou Bay (XKB) regions of Taihu Lake for bacterioplankton, microeukaryotes and inter-kingdom community

Summary

Introduction

Microorganisms are crucial components of aquatic ecosystems, and play important roles in the ecological processes in freshwater lakes[1,2]. Species interact with each other in various ways (such as competition and mutualism), which leads to the formation of complicated networks[3,4,5,6] An understanding of these interactions between taxa in bacterioplankton, microeukaryotes and the inter-kingdom (bacterioplankton and microeukaryotes combined) communities may help us to clarify their functional roles or environmental niches in the ecosystem[7,8,9]. The network and co-occurrence patterns of the bacterioplankton and microeukaryotes communities in regions with different nutrient loading levels may be disparate, and it is important to understand how they are influenced by the nutritional status. We sought to answer the following questions: (1) Are the interactions among microbial communities the same in regions with different nutrient loading levels? (2) Are these interactions different between bacterioplankton, microeukaryotes and inter-kingdom? (3) Are the relationships between environmental factors and the network of microbial communities different between regions with different nutrient loading levels?

Methods

Results

Conclusion