Distinct Successions of Common and Rare Bacteria in Soil Under Humic Acid Amendment - A Microcosm Study.

Pengfa Li,Ming Liu,Meng Wu,Zhongpei Li,Jia Liu,Chunyu Jiang

doi:10.3389/fmicb.2019.02271

Abstract

Humic acid (HA) is widely used for soil quality improvement, yet little is known how bacterial communities, especially common and rare bacteria, respond to HA amendment, which is crucial to understand biodiversity and function in agroecosystem. Therefore, a manipulated microcosm experiment with a gradient of HA amendment was conducted to unveil this. The results showed that common and rare taxa had similar patterns in species richness, while rare taxa exhibited a higher turnover, which caused their higher structural dissimilarity. Common species with wider niche breadths were more strongly influenced by deterministic filtering when compared to rare taxa, which occupied narrow niches and were primarily controlled by stochastic processes. Generally, species with wider niche breadths were always more strongly influenced by deterministic selection. The analysis of predicted functions revealed that rare taxa occupied more unique predicted functional traits than common taxa, suggesting that rare taxa played a key role in maintaining the functional diversity. In addition, there was a significant positive correlation between species richness and predicted functional diversity in rare taxa rather than common taxa. Our findings highlight the distinct structural and predicted functional successions of common and rare bacteria in soil under HA amendment.

Highlights

Humic substances are the most widely-spread natural complexing ligands occurring in nature, of which humic acid (HA) is the most explored group of humic substances, and the remarkable properties of Humic acid (HA) have attracted the attention of many investigators (Peña-Méndez et al, 2005)
The species composition of common taxa was similar to that of all taxa, while Planctomycetes, Gammaproteobacteria, and Delta-proteobacteria were dominant in rare taxa (Supplementary Figure S1)
Each KEGG orthologs (Kos) was treated as a functional trait, and we found that predicted functional diversity showed no significant difference among treatments across all three datasets (Supplementary Figure S5)

Summary

Introduction

Humic substances are the most widely-spread natural complexing ligands occurring in nature, of which humic acid (HA) is the most explored group of humic substances, and the remarkable properties of HA have attracted the attention of many investigators (Peña-Méndez et al, 2005). How soil bacterial communities respond to HA amendment, which is crucial to Succession in Common and Rare Bacteria understanding biodiversity and function in agroecosystem, is little known. This calls for further investigation on successions of soil bacterial communities under HA amendment. There are two divergent patterns describing the succession in species compositions of bacterial communities, turnover and nestedness (Harrison et al, 1992; Baselga, 2010). Some rare microbial taxa have been shown to provide specific and important functions within their communities, such as establishing a functional cache or resource pool for responding to environmental changes (Jones and Lennon, 2010), maintaining species diversity (Dohrmann et al, 2013), and promoting functional redundancy (Louca et al, 2018). A lack of understanding of the successional patterns of common and rare taxa have largely limited our ability to better predict the variations in structure and ecological functions of bacterial communities

Methods

Results

Discussion

Conclusion