Geographical Variability of Mineral Elements and Stability of Restrictive Mineral Elements in Terrestrial Cyanobacteria Across Gradients of Climate, Soil, and Atmospheric Wet Deposition Mineral Concentration.

Weibo Wang,Quanfa Zhang,Yuyi Yang,René Guénon,Xiaoli Cheng,Xiao Shu,Hua Li

doi:10.3389/fmicb.2020.582655

Abstract

Terrestrial cyanobacteria Nostoc commune is an ideal species to study the geographical variation of mineral elements of soil cyanobacteria at the species level. Here, we first address the following questions: (1) from where are these mineral elements, (2) are there geographical variations for these mineral elements, and if so, (3) which environmental factors drive the geographical variation of these mineral elements? Second, we tested whether the soil cyanobacterial mineral elements followed the “restrictive element stability hypothesis” of higher plants. Finally, we explored the effect of mineral geographic variation on ecological adaptation of soil cyanobacteria. We collected N. commune samples across gradients of climate, soil, and atmospheric wet deposition mineral concentration in mainland China. We measured fifteen minerals, including five macroelements (N, Ca, K, Fe, P), five microelements (Mn, Zn, Cu, Co, Se), and five heavy metals (Pb, Cr, As, Cd, Hg). We found that five elements (P, Cu, Zn, Co, Pb) had significant geographical variation. They increased as the distance from the equator increased and decreased as the distance from the prime meridian increased. Mean annual precipitation and mean annual temperature explained most of the variation. We did not find any significant correlations between the mineral element contents in N. commune and the minerals in soil and rainfall, except for P. There was no significant correlation between the variation coefficients of different elements and their actual detected contents and their potential physiological required contents. The statistical results of our experiment did not support the “restrictive element stability hypothesis.” We speculated that net accumulation of mineral elements in cyanobacterial cells and extracellular polysaccharides (EPS) might play an important role for terrestrial cyanobacteria in the adaptation to dry and cold conditions.

Highlights

Significant progress has been achieved in terrestrial microbial biogeography (Fierer and Jackson, 2006; Ranjard et al, 2010, 2013)
We focused on 15 mineral elements of N. commune (Figure 1) and investigated the geographical variation of mineral elements of soil microorganisms at the species level in mainland China
We addressed the following questions: (1) from where are these mineral elements, (2) are there geographical variations for these mineral elements in N. commune like those of higher plants or aquatic algae, and (3) which environmental factors dominate the geographical variation of these mineral elements? Second, we tested whether the soil cyanobacterial mineral elements followed the higher plants “restrictive element stability hypothesis” (Han et al, 2011), which implies that variability is lowest for elements that are required in the highest concentrations

Summary

Introduction

Significant progress has been achieved in terrestrial microbial biogeography (Fierer and Jackson, 2006; Ranjard et al, 2010, 2013). For aquatic microorganisms and higher plants and animals, the geographical variation of their community structure and the variation of their biochemical composition and mineral elements (stoichiometric characteristics) can be studied, both at the community level (Han et al, 2005, 2011; Yvon-Durocher et al, 2015) and the species level (Zhou et al, 2013; Garcia et al, 2016; Brady and Seth, 2017; Godwin and Cotner, 2018). Studies on terrestrial microbial geography mainly focus on the geographical variation of microbial community structure (Garcia-Pichel et al, 2013), while geographical variations in its biochemical composition and mineral elements (stoichiometric characteristics) are rarely reported. The biochemical composition and mineral elements of microbial biomass from artificial propagation may change relative to naturally growing microorganisms due to the difference in its environment (Dawson, 1919)

Methods

Results

Discussion

Conclusion