Full length ArticleCharacterization of heavy metal toxicity in some plants and microorganisms—A preliminary approach for environmental bioremediation
Graphical abstract
Introduction
Industrialization and modern agriculture have increased environmental contamination with heavy metals, which can accumulate in living organisms, causing the emergence of toxicity symptoms [[1], [2], [3], [4], [5], [6]]. Although several heavy metals (Co, Cu, Cr, Ni, Fe, Mn, Zn etc.) play a vital role in the metabolic processes in enzymatic reactions and in providing osmotic balance [[7], [8], [9]], some others (Cr, Cd, Hg, Ni, Pb) are toxic, inhibiting growth to different extents, even at very low concentrations [1,3,[8], [9], [10], [11], [12]]. An excessive accumulation of heavy metals in aquatic and soil environments can induce adverse phytotoxic effects, such as growth inhibition, photosynthesis disturbance, biomass decrease, and nutrient uptake deficiency [[13], [14], [15]].
Plants growing on soils contaminated with heavy metals are able to absorb significant amounts of metal ions, which thus enter the food chain affecting human health [[16], [17], [18], [19], [20]]. Likewise, some microorganisms living in the soil can accumulate heavy metals, since they are able to initiate and develop various mechanisms for metal mobilization or immobilization (e.g. biosorption, bioprecipitation), depending on soil properties (pH, type, salinity etc.) [21]. Hence, the cleanup of contaminated soils using plants, microorganisms or other biological systems, within the limits of their tolerance for heavy metals and under controlled conditions, remains a constant challenge for researchers and for regulatory authorities [1,3,13,[21], [22], [23]].
Cr and Cd were selected for this study since they are recognized as frequently-encountered toxic heavy metals and were categorized as human carcinogens by the International Agency for Research on Cancer in 1993 [[24], [25], [26], [27]]. They are very toxic to both plants and microorganisms, whose response to any stress generated by heavy metals depends on the heavy metal concentration, type and speciation, but also on environmental factors and organism species [[28], [29], [30], [31], [32], [33], [34]]. Cd can play the role of cofactor for oxidative reactions that disrupt and damage living tissues, and can increase the oxidative capacity in the generation of reactive-oxygen species (ROS), lipid peroxidation and depleting glutathione, enhancing and linking protein sulfhydryl groups [[35], [36], [37]]. The reduction/oxidation of Cr from Cr(VI) to Cr(III) is possible from a thermodynamic point of view in certain physiological conditions. Cr(VI) is the most toxic form of Cr, often found as oxyanions associated with oxygen, as chromate (CrO42) or dichromate (Cr2O72−) [17]. It is acknowledged that Cr(III) is indispensable for sustaining the glucose metabolism of lipids and proteins. In addition, Cr(III) can stabilize the tertiary structure of proteins, RNA and DNA conformation. On the other hand, the compounds of Cr(VI) are toxic. Interactions between bacteria, algae, fungi and plants, with Cr and its compounds have been thoroughly reviewed in the literature [12,15,17,38,39].
Here, the phytotoxicity of Cr(VI) and Cd(II) has been tested by investigating their effects on the efficiency of seed germination and growth process of the plant Lepidium sativum. Studies on the ecotoxicity of Cr(VI) and Cd(II) using bacteria (Azotobacter sp.) and fungi (Pichia sp.) isolated from the soil were also developed.
Section snippets
Heavy metals, plants and microorganisms
Stock solutions of 1000 mg/L K2Cr2O7 and Cd(NO3)2·4H2O (Riedel) were prepared weekly and checked daily in terms of their concentration, of which we prepared working solutions with concentrations ranging between 30−300 mg/L (5.77 × 10−4–57.7 × 10−4 mol Cr(VI)/L and 2.67 × 10−4–26.7 × 10−4 mol Cd(II)/L, respectively). Cd(II) concentrations in aqueous solution were determined using a spectrophotometric method with xylenol orange at 575 nm [40]. Cr(VI) concentrations in aqueous solution were
Chromium and cadmium phytotoxicity for L. sativum
Several criteria can be used to assess phytotoxicity, such as [54]:
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frequency (number of plants showing a visual symptom at a certain stage of growth);
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measurements (plant height, length, diameter, weight, or organs from a sample).
In this experimental program the influence was assessed of various concentrations of Cr(VI) and Cd(II) metal ions on L. sativum seed germination, root development, stem length and biomass weight, compared to a similar group grown in the absence of toxic compounds
Conclusions
The need for information about heavy metal levels in the environment (water, soil), their mobility, availability and toxicity in plants and microorganisms was addressed in this study as a preliminary approach in supporting decision making which demands the most appropriate bioremediation strategies. The studies revealed the adverse effects of heavy metal ions, Cr(VI) and Cd(II) on an edible plant (L. sativum) and growth of two microorganisms (Azotobacter sp., Pichia sp.), depending on metal
Acknowledgements
This paper was elaborated with the support of two grants of the Romanian National Authority for Scientific Research, CNCS – UEFISCDI: project number PN-II-ID-PCE-2011-3-0559, Contract 265/2011, http://persenvir.xhost.ro; project number PN-III-P4-ID-PCE-2016-0683, Contract 65/2017, http://bioremip.xhost.ro.
The authors are very grateful to Professor Dumitru Bulgariu from “Al.I. Cuza” University of Iasi, Romania, Faculty of Geography and Geology, Department of Geology and Geochemistry for his
References (76)
- et al.
A review on heavy metal pollution, toxicity and remedial measures: current trends and future perspectives
J Mol Liq
(2019) - et al.
Toxicity of heavy metals to microorganisms and microbial processes in agricultural soils: a review
Soil Biol Biochem
(1998) - et al.
Do toxic heavy metals affect antioxidant defense mechanisms in humans?
Ecotoxicol Environ Saf
(2012) The biochemistry of chromium
J Nutr
(2000)- et al.
Chromium toxicity in plants
Environ Int
(2005) - et al.
Rhizobacteria and plant symbiosis in heavy metal uptake and its implications for soil bioremediation
N Biotechnol
(2017) - et al.
Growth and protein profile changes in Lepidium sativum L. plantlets exposed to cadmium
Environ Exp Bot
(2007) - et al.
Importance of nitric oxide in cadmium stress tolerance in crop plants
Plant Physiol Biochem
(2013) - et al.
Experimental analysis and mathematical prediction of Cd(II) removal by biosorption using support vector machines and genetic algorithms
N Biotechnol
(2015) - et al.
Mitochondria, reactive oxygen species and cadmium toxicity in the kidney
Toxicol Lett
(2010)
Cadmium inhibits the electron transfer chain and induces reactive oxygen species
Free Radic Biol Med
Free radicals, metals and antioxidants in oxidative stress–induced cancer
Chem Biol Interact
Indole acetic acid differently changes growth and nitrogen metabolism in Pisum sativum L. seedlings under chromium (VI) phytotoxicity: implication of oxidative stress
Sci Hortic
Interactions of chromium with micro-organisms and plants
FEMS Microbiol Rev
Prosopis laevigata a potential chromium(VI) and cadmium(II) hyperaccumulator desert plant
Bioresour Technol
Mannitol alleviates chromium toxicity in wheat plants in relation to growth, yield, stimulation of anti–oxidative enzymes, oxidative stress and Cr uptake in sand and soil media
Ecotoxicol Environ Saf
Chromium induced lipid peroxidation in the plants of Pistia stratiotes L.: role of antioxidants and antioxidant enzymes
Chemosphere
A simple kinetic approach to derive the ecological dose value ED(50), for the assessment of Cr(VI) toxicity to soil biological properties
Soil Biol Biochem
Bioremediation of heavy metals by microalgae
Kinetics of soil dehydrogenase in response to exogenous Cd toxicity
J Hazard Mater
Molecular mechanism on cadmium-induced activity changes of catalase and superoxide dismutase
Int J Biol Macromol
Bioavailability of heavy metals from polluted soils to plants
Sci Total Environ
Soil metal pollution related to active Buchim copper mine, Republic of Macedonia
Environ Eng Manage J
Biosorption in environmental remediation
Modelling and simulation of heavy metals transport in water and sediments
Environ Eng Manage J
Heavy metals toxicity and the environment
Experentia
Trace metal metabolism in plants
J Exp Bot
Cadmium stress tolerance in crop plants. Probing the role of sulfur
Plant Signal Behav
Antimicrobial activity of metals: mechanisms, molecular targets and applications
Nat Rev Microbiol
Symbiosis in the environment biomanagement of soils contaminated with heavy metals
Eur J Sci Theol
Removal of heavy metals from the environment by biosorption
Eng Life Sci
The effect of heavy metals on mite communities (acari: gamasina) from urban parks - Bucharest, Romania
Environ Eng Manage J
Effects of heavy metals on Lepidium sativum germination and growth
Environ Eng Manage J
Metal hyperaccumulation in plants – biodiversity prospecting for phytoremediation technology
Electron J Biotechnol
Heavy metals content and essential oil yield of Juniperus phoenicea l. In different origins in Jordan
Environ Eng Manage J
Mechanisms of stress avoidance an tolerance by plants used in phytoremediation of heavy metals
Arch Environ Prot
Phytoaccumulation, competitive adsorption and evaluation of chelators-metal interaction in lettuce plant
Environ Eng Manage J
Recent advances in biosorption of heavy metals; support tools for biosorption equilibrium, kinetics and mechanism
Rev Roum Chim
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