Environmental filtering of bacterial functional diversity along an aridity gradient

Ho-Kyung Song,Teng Yang,Jin-Sheng He,Haiyan Chu,Hyoki Kim,Jonathan M Adams,Piotr Jablonski,Yu Shi

doi:10.1038/s41598-018-37565-9

Abstract

Studying how metagenome composition and diversity varies along environmental gradients may improve understanding of the general principles of community and ecosystem structuring. We studied soil bacterial metagenomes along a precipitation gradient on the eastern Tibetan Plateau, varying between 500 mm and 60 mm mean annual precipitation (MAP). We found that lower MAP was strongly associated with reduced functional diversity of bacterial genes. It appears that extreme environmental conditions associated with aridity constrain the diversity of functional strategies present in soil biota – analogous to broad scale patterns found in plant functional diversity along environmental gradients. In terms of specific functions, more extreme arid conditions were also associated with increased relative abundance of genes related to dormancy and osmoprotectants. Decreased relative abundance of genes related to antibiotic resistance and virulence in more arid conditions suggests reduced intensity of biotic interaction under extreme physiological conditions. These trends parallel those seen in earlier, more preliminary comparisons of metagenomes across biomes.

Highlights

Soil metagenomes can potentially reveal patterns of variation in functionality of soil biota – and from these the general ecological patterns of community structure and ecosystem function[1]
We show in a field based observational study how total functional diversity and the relative abundance of gene categories varies with a broad scale aridity trend
Our findings mostly parallel those seen in earlier studies of arid environments such as Fierer et al.24 - which demonstrated functional differences of microbial community in desert biome compared to non-desert biomes in a worldwide scale - or Tripathi et al.[22], which compared the functional profile of microbes in arid, semi-arid, Mediterranean, and humid Mediterranean environments in Israel

Summary

Introduction

Soil metagenomes can potentially reveal patterns of variation in functionality of soil biota – and from these the general ecological patterns of community structure and ecosystem function[1]. Theory and observation of larger organisms, notably plants, has both predicted and observed broad scale gradients in the diversity of functional traits along climatic stress gradients[2,3,4] The authors of those studies suggested that extreme physiological conditions and reduced energy budgets for organisms constrain the number of different functional strategies which are viable in a particular environment. Maestre et al.[5] studied microbial community structure in a wide range of global drylands They found that microbial diversity decreased along a gradient of increasing aridity, and that relative abundances of major groups of bacteria and fungi are correlated with the degree of aridity. Correspondence and requests for materials should be addressed to www.nature.com/scientificreports/

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