Abstract
Miscanthus spp. are energy plants and excellent candidates for phytoremediation approaches of metal(loid)s-contaminated soils, especially when combined with plant growth-promoting bacteria. Forty-one bacterial strains were isolated from the rhizosphere soils and roots tissue of five dominant plants (Artemisia argyi Levl., Gladiolus gandavensis Vaniot Houtt, Boehmeria nivea L., Veronica didyma Tenore, and Miscanthus floridulus Lab.) colonizing a cadmium (Cd)-contaminated mining area (Huayuan, Hunan, China). We subsequently tested their plant growth-promoting (PGP) traits (e.g., production of indole-3-acetic acid, siderophore, and 1-aminocyclopropane-1-carboxylate deaminase) and Cd tolerance. Among bacteria, two strains, Klebsiella michiganensis TS8 and Lelliottia jeotgali MR2, presented higher Cd tolerance and showed the best results regarding in vitro growth-promoting traits. In the subsequent pot experiments using soil spiked with 10 mg Cd·kg−1, we investigated the effects of TS8 and MR2 strains on soil Cd phytoremediation when combined with M. floridulus (Lab.). After sixty days of planting M. floridulus (Lab.), we found that TS8 increased plant height by 39.9%, dry weight of leaves by 99.1%, and the total Cd in the rhizosphere soil was reduced by 49.2%. Although MR2 had no significant effects on the efficiency of phytoremediation, it significantly enhanced the Cd translocation from the root to the aboveground tissues (translocation factor > 1). The combination of K. michiganensis TS8 and M. floridulus (Lab.) may be an effective method to remediate Cd-contaminated soils, while the inoculation of L. jeotgali MR2 may be used to enhance the phytoextraction potential of M. floridulus.
Highlights
To isolate rhizosphere soil bacteria, approximately 1.0 g of rhizospheric soil was dissolved in 10 mL sterile distilled water (10−1 ), 0.5 mL 10−1 soil solution was added into 4.5 mL sterile distilled water (10−2 ), and the soil solution was diluted to 10−8 by ten times gradient successively; afterward, 100 μL diluted solution (10−6, 10−7 and 10−8 ) was spread on Luria–Bertani (LB) agar media, Plants 2021, 10, 912 and incubated at 30 ◦ C for 24 h
We found that the TS8 strain (1.41 μmol α-Kb/(h·mg)) showed significantly higher
We investigated the effects of L. jeotgali MR2 and K. michiganensis TS8 on M. floridulus (Lab.) ability of remediating Cd, and found that TS8 reduced the total Cd concentration in the rhizosphere soil from 10 to 5.08 mg/kg, showing an increase in remediation efficiency of about 8.1% (49.23%) if compared to the control (45.53%)
Summary
Metal(loid)s pollution is a serious problem that results from rapid industrial development, leading to the contamination of several ecosystems, including rivers and soils, further affecting human and animal health through the food chain. Among these toxic trace elements, cadmium (Cd) has attracted widespread concern due to its high toxicity, causing cancer incidence, osteoporosis, and even death [1]. China is one of the largest rice producers globally, and Hunan Province is one of China’s main rice-producing areas. Previous studies reported that many arable lands in Hunan Province are contaminated with. The remediation of Cd-contaminated soil in Hunan Province is an urgent task
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