Abstract

Bioremediation is an ecologically-friendly approach for the restoration of heavy metal-contaminated sites and can exploit environmental microorganisms such as bacteria and fungi. These microorganisms are capable of removing and/or deactivating pollutants from contaminated substrates through biological and chemical reactions. Moreover, they interact with the natural flora, protecting and stimulating plant growth in these harsh conditions. In this study, we isolated a group of endophytic fungi from Agrostis stolonifera grasses growing on toxic waste from an abandoned lead mine (up to 47,990 Pb mg/kg) and identified them using DNA sequencing (nrITS barcoding). The endophytes were then tested as a consortium of eight strains in a growth chamber experiment in association with the grass Festuca arundinacea at increasing concentrations of lead in the soil to investigate how they influenced several growth parameters. As a general trend, plants treated with endophytes performed better compared to the controls at each concentration of heavy metal, with significant improvements in growth recorded at the highest concentration of lead (800 galena mg/kg). Indeed, this set of plants germinated and tillered significantly earlier compared to the control, with greater production of foliar fresh and dry biomass. Compared with the control, endophyte treated plants germinated more than 1-day earlier and produced 35.91% more plant tillers at 35 days-after-sowing. Our results demonstrate the potential of these fungal endophytes used in a consortium for establishing grassy plant species on lead contaminated soils, which may result in practical applications for heavy metal bioremediation.

Highlights

  • Lead (Pb) is classified as a “heavy metal” due to its high relative atomic weight (>4 g/cm3 ).Some metals are essential to plant growth such as zinc and manganese, but lead does not have any known biological function and is toxic to plants even at low concentration [1]

  • A total of 62 microorganism cultures were isolated from Agrostis stolonifera roots collected from the three waste heaps at the Ballycorus mine site (Figure 2)

  • SP02 was the original site used for lead ore and solid waste produced by these excavations are still accumulated at the edge of the heap representing the main volume of exposed mine waste

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Summary

Introduction

Some metals are essential to plant growth such as zinc and manganese, but lead does not have any known biological function and is toxic to plants even at low concentration [1]. It is, known as a toxic heavy metal (THM) and causes high levels of environmental pollution due to its extreme toxicity [2,3]. Lead is naturally present in rock formations within the Earth’s crust that becomes increasingly available in the biosphere due to human interference. Due to its non-biodegradable nature, it persists in the environment for a long time and becomes available

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