Plant Species and Heavy Metals Affect Biodiversity of Microbial Communities Associated With Metal-Tolerant Plants in Metalliferous Soils.

Sławomir Borymski,Mariusz Cycoń,Luis A J Mur,Zofia Piotrowska-Seget,Manfred Beckmann

doi:10.3389/fmicb.2018.01425

Abstract

We here assess the biodiversity of the rhizosphere microbial communities of metal-tolerant plant species Arabidopsis arenosa, Arabidopsis halleri, Deschampsia caespitosa, and Silene vulgaris when growing on various heavy metal polluted sites. Our broad-spectrum analyses included counts for total and metal-tolerant culturable bacteria, assessments of microbial community structure by phospholipid fatty acid (PLFA) profiling and community-level analysis based on BIOLOG-CLPP to indicate functional diversity. The genetic-biochemical diversity was also measured by denaturing gradient gel electrophoresis (PCR-DGGE) and metabolomic analysis (HPLC-MS). Different rhizospheres showed distinctive profiles of microbial traits, which also differed significantly from bulk soil, indicating an influence from sampling site as well as plant species. However, total bacterial counts and PCR-DGGE profiles were most affected by the plants, whereas sampling site-connected variability was predominant for the PLFA profiles and an interaction of both factors for BIOLOG-CLPP. Correlations were also observed between pH, total and bioavailable Cd or Zn and measured microbial traits. Thus, both plant species and heavy-metals were shown to be major determinants of microbial community structure and function.

Highlights

Heavy metals pose a serious threat to soil organisms and the entire ecosystem when they occur at excessive amounts
The pH values were generally higher in W-derived samples, regardless of the sample origin, with the highest score recorded in the rhizosphere of S. vulgaris
The highest values of this parameter were recorded for D. caespitosa and A. halleri rhizospheres collected at the N sampling site

Summary

Introduction

Heavy metals pose a serious threat to soil organisms and the entire ecosystem when they occur at excessive amounts. Since the early work of Lorenz Hiltner, who coined a term “rhizosphere” in 1904, it is known that plants create a specific niche where microbial growth and activity become intensified (Hartmann et al, 2008) This rhizosphere effect is thought to arise from the deposition of various organic compounds from plants into the soil (Prashar et al, 2014). Plants exudate a variety of small and high molecular weight organic as well as inorganic compounds that enrich rhizosphere in nutrients that attract and stimulate soil microbial communities. For this reason, rhizosphere microbial communities tend to have higher microbial counts and generally show higher activity than those occurring in bulk soil. Plant-related compounds released to soil environment may act as messengers that initiate interactions between roots and a wide range of soil organisms (Perrine-Walker et al, 2011)

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