Phytoextraction efficiency of Pteris vittata grown on a naturally As-rich soil and characterization of As-resistant rhizosphere bacteria

Abstract

This study evaluated the phytoextraction capacity of the fern Pteris vittata grown on a natural arsenic-rich soil of volcanic-origin from the Viterbo area in central Italy. This calcareous soil is characterized by an average arsenic concentration of 750 mg kg−1, of which 28% is bioavailable. By means of micro-energy dispersive X-ray fluorescence spectrometry (μ-XRF) we detected As in P. vittata fronds after just 10 days of growth, while a high As concentrations in fronds (5,000 mg kg−1), determined by Inductively coupled plasma-optical emission spectrometry (ICP-OES), was reached after 5.5 months. Sixteen arsenate-tolerant bacterial strains were isolated from the P. vittata rhizosphere, a majority of which belong to the Bacillus genus, and of this majority only two have been previously associated with As. Six bacterial isolates were highly As-resistant (> 100 mM) two of which, homologous to Paenarthrobacter ureafaciens and Beijerinckia fluminensis, produced a high amount of IAA and siderophores and have never been isolated from P. vittata roots. Furthermore, five isolates contained the arsenate reductase gene (arsC). We conclude that P. vittata can efficiently phytoextract As when grown on this natural As-rich soil and a consortium of bacteria, largely different from that usually found in As-polluted soils, has been found in P. vittata rhizosphere.

Phyto-Beneficial Traits of Rhizosphere Bacteria: In Vitro Exploration of Plant Growth Promoting and Phytopathogen Biocontrol Ability of Selected Strains Isolated from Harsh Environments

“…Identified at the genera and species level by 16S rDNA sequencing, and only partially characterized for their putative PGPR properties, bacteria strains elected for this work belonged to differently demanding environments: Pvr_5 and Pvr_9 were isolated from the rhizosphere of the As-hyperaccumulating fern Pteris vittata [27], PHA_1 from a soil rich in hydrocarbons [28], NCr-1 was found to be an endophyte of the Ni-hyperaccumulator Noccaea caerulescens [25], and Bioch_2 and Bioch_7 were isolated from a third-year biocharamended soil [26]. In this work, for this purpose, a deeper characterization of the selected bacterial strains was performed.…”

“…In this study, a deeper characterization of six different bacterial strains previously isolated from different environments was performed. As reported in Table 1, the selected strains Pvr_5, and Pvr_9, Bioch_2, Bioch_7, NCr-1 showed some features of PGPR as high in vitro IAA production and 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase activity (Table 1) [25][26][27], as well as the production of siderophores, which was diagnosed by using a qualitative method [25][26][27]. In this work, a liquid chrome azurol S (CAS) assay was used to evaluate the siderophore production in a semiquantitative manner.…”

“…Six bacterial strains isolated from different sources were selected for this work from a collection of PGPR present in our laboratory: Bioch_2 (homologous to Arthrobacter defluvii) and Bioch_7 (homologous to Arthrobacter nicotinovorans) strains were previously isolated by a maize-derived biochar utilized as amendment in a three year poplar short rotation coppice plantation [26]; Ncr-1 (homologous to Arthrobacter sp.) is an endophyte strain isolated from the roots of the Ni-hyperaccumulator Noccaea caerulescens [27]; PHA_1 (homologous to Pseudomonas protegens) was isolated from a soil contaminated with hydrocarbons [28]; Pvr_5 (homologous to Paenarthrobacter ureafaciens); and Pvr_9 (homologous to Beijerinckia fluminensis) were isolated from the rhizosphere of the As-hyperaccumulator Pteris vittata fern [25]. PGPR characteristics were reported in Table 1.…”

Bacterial Microbiome in the Phyllo-Endosphere of Highly Specialized Rock Spleenwort

“…Many studies considered bacterial taxa enhancing plant defense ( Matsumoto et al, 2021 ; Cernava and Berg, 2022 ; Shalev et al, 2022 ) besides other plant growth-promoting functions ( Glick, 2012 ; Backer et al, 2018 ; Leontidou et al, 2020 ), but current studies expanded their focus on a wide range of ecological aspects such as the contribution of bacterial communities to the rapid adaption to local environments enforced by bacterial communities ( Li et al, 2021 ) that coincide with diversification patterns ( Abedlfattah et al, 2021 ) as argued in the SYMPHY proposal ( Tripp et al, 2017 ) and the Plant Holobiont Theory ( Lyu et al, 2021 ). Notable aspects studied include the enhanced resistance of plants to environmental stresses supported by endophytic bacteria, e.g., salt tolerance ( Vaishnav et al, 2019 ) and heavy metal tolerance ( Zhu et al, 2014 ; Xu et al, 2016 ; Gu et al, 2018 ; Banach et al, 2020 ; Yang et al, 2020 ; Antenozio et al, 2021 ) or even support the adaptation to extreme environments, e.g., deserts ( Zhang et al, 2019 ) and karst habitats ( Li F. et al, 2019 ). Endophytic bacteria have been also considered as promoters of horizontal gene transfer ( Tiwari and Bae, 2020 ; Zilber-Rosenberg and Rosenberg, 2021 ).…”

Advanced Drinking Groundwater As Phytofiltration by the Hyperaccumulating Fern Pteris vittata

“…Arsenic contamination of drinking and irrigation water is an important threat to public health [3,4] and current European legislation imposes a limit of 10 µg/L for As concentration in water for human consumption. In several volcanic areas this limit is highly exceeded because of natural mineral release from soil to underground aquifers [5][6][7]. As a consequence of the excess of As concentration, in Viterbo and the surrounding area (Lazio, Italy), dearsenification of drinking water is performed by means of filtering devices.…”