Elsevier

Science of The Total Environment

Volume 624, 15 May 2018, Pages 1106-1118
Science of The Total Environment

Remediation of arsenic in mung bean (Vigna radiata) with growth enhancement by unique arsenic-resistant bacterium Acinetobacter lwoffii

https://doi.org/10.1016/j.scitotenv.2017.12.157Get rights and content

Highlights

  • Acinetobacter lwoffii stopped arsenic uptake, enhanced mung bean growth in 7 days.

  • The microbe produced plant growth promoting agents in absence, in presence of arsenic.

  • Oxidative stress caused by arsenic in mung bean was reduced by the bacteria.

  • Acinetobacter lwoffii (RJB-2) formed biofilm which helped in arsenic resistance.

  • Distribution pattern of arsenic in plant gives better understanding of bioremediation.

Abstract

Arsenic, a carcinogenic and toxic contaminant of soil and water, affects human health adversely. During last few decades, it has been an important global environmental issue. Among several arsenic detoxification methods remediation using arsenic resistant microbes is proved to be environment-friendly and cost-effective. This study aimed to test the effects of arsenic utilizing bacterial strain Acinetobacter lwoffii (RJB-2) on arsenic uptake and growth of mung bean plants (Vigna radiata). RJB-2 exhibited tolerance up to 125 mM of arsenic (V) and 50 mM of arsenic (III). RJB-2 produced plant growth promoting substances e.g. indole acetic acid (IAA), siderophores, exopolysaccharide (EPS) and phosphate solubilization in the absence and in presence of arsenic. Pot experiments were used to scrutinize the role of RJB-2 on arsenic uptake and growth of mung bean plants grown in soil amended with 22.5 mg kg 1 of sodium arsenate (Na2HAsO4·7H2O). RJB-2 could arrest arsenic uptake in just 7 days and increase plant growth, number of plants per pot, chlorophyll and carotenoid content of the mung bean plants. RJB-2 formed biofilm and its root-association helped to abate arsenic uptake in mung bean. Confocal and light microscopic studies also revealed the abatement of arsenic uptake and increase in chlorophyll content in mung bean plants in presence of RJB-2. RJB-2 was also responsible for less production of reactive oxygen species (ROS) in mung bean plants reducing the oxidative damage caused by arsenic. The lower percentage of electrolytic leakage (EL) in RJB-2 inoculated mung bean plants proved arsenic abatement. The study also reported the distribution of arsenic in various parts of mung bean plant. RJB-2 owing to its intrinsic abilities of plant growth promotion even in presence of high concentrations of arsenic could inhibit arsenic uptake completely and therefore it could be used in large-scale cultivation for phytostabilization of plants.

Introduction

Arsenic pollution is a serious environmental problem throughout the world (Meharg, 2004, Pandey, 2006). Various drinking wells of Bangladesh and a large part of East India, mainly the regions in West Bengal are contaminated with arsenic and thus causing large-scale exposure of arsenic to population directly by drinking of water and indirectly through consumption of food grown in soil and water contaminated with arsenic (Rahman et al., 2014, Chakraborti et al., 2015). The soaking of croplands by arsenic-contaminated water causes its accumulation in the soil (Abedin et al., 2002) and thus leading to arsenic uptake by plants. Soil content of arsenic may alter depending upon the severity of the contamination (Singh and Ma, 2007) and may rise to a concentration as high as 2600 mg kg 1 in the soil of mineralized zones (Meharg et al., 1994b). Arsenic is also found in plant edible parts such as fruits, leaves and seeds and hence they become unsafe for human consumption (Rosas-Castor et al., 2014).

Arsenic interferes with the plant's metabolism resulting in disorders at several organizational levels and inhibits plant growth (Marin et al., 1993, Meharg, 1994). Once arsenic enters into plant cells, it causes damage to plant parts in several ways which include interference in aerobic phosphorylation and reduction of arsenate to arsenite inside the plant cells, targeting sulfhydryl groups of proteins (Schmoger et al., 2000). Arsenic causes interference in plant metabolism as it competes with phosphate [PO43 ]. Since PO43  and arsenate [AsO43 ] have similar structures both are carried by the PO43  transporters in plants (Han et al., 2016). Arsenic produces adenosine diphosphate (ADP)–As, in place of adenosine triphosphate (ATP) and energy flow is disrupted in plant cells (Meharg, 1994). This causes a reduction in plant growth and yield (Carbonell-Barrachina et al., 1995), discoloration of roots, leaf necrosis, root plasmolysis and a decrease in photosynthetic capacity of a plant (Marin et al., 1993, Meharg, 1994). Therefore arsenic gets entry into plant edible parts such as fruits, leaves, and seeds (Abedin et al., 2002). The concentration of arsenic varies based on the type of plant species (Cobb et al., 2000). It has also been known that soil arsenic interferes in uptake and accumulation of minerals into plant shoots and seeds (Paivoke and Simola, 2002, Milivojevic et al., 2006) and their nutritional composition may be influenced (Tu and Ma, 2005).

Contamination and poisoning caused by arsenic (arsenicosis) cause diseases like skin lesions, skin cancer, bladder, kidneys, and lung cancer, high blood pressure, blindness, partial paralysis and reproductive disorders (Chatterjee and De, 2015, Das and Sarkar, 2016, Álvarez-Ayuso et al., 2016, Mir et al., 2007). Pteris vittata (brake fern) is the first known hyperaccumulator of arsenic. The growth of Pteris vittata can be enhanced by the presence of arsenic as much as 46% (Xu et al., 2014). Other ferns, like P. cretica, P. umbrosa, and P. longifolia are also able to grow properly in arsenic polluted soils and accumulate a large amount of arsenic in their fronds (Ma et al., 2001, Meharg, 2003).

Although several detoxification methods such as containment, stabilization, and solidification etc. have been proposed for the remediation of onsite polluted soils, appropriate controls are needed by all of these methods and long-term monitoring to ensure the behavior of arsenic through soil column (Chang et al., 2011). Significant importance is given to arsenic-tolerant bacteria having plant growth promoting (PGP) traits and capability to arrest arsenic uptake, pollution (Das et al., 2016). The application of arsenic utilizing bacteria for bioremediation is an eco-friendly and cost-effective process if compared with other techniques (Das et al., 2016). Rhizospheric microbes interact with plants influencing their growth, increasing water uptake and mineral with the production of antimicrobial compounds to inhibit soil pathogens and produce plant growth regulators (Mishra et al., 2009).

Mung bean (Vigna radiata) is a rich source of seed proteins. Some studies reported growth of mung bean in an arsenic-contaminated environment (Singh et al., 2007). Arsenic causes the reduction in both seed germination and growth of mung bean plants causing loss of crop productivity and hence it is toxic for mung bean. There are reports showing that bacteria inoculation has abated arsenic toxicity in economically important crops like rice (Oryza sativa L.) (Das et al., 2016, Lakshmanan et al., 2015), chickpea (Cicerarietinum L.) (Srivastava and Singh, 2014), Indian mustard plant (Brassica juncea (L.) Czernetc.) (Srivastava et al., 2013) etc. However, the study related to detailed effects of microbes on the growth and crop yield of mung bean grown in the arsenic-contaminated area is largely unexcavated.

In the current study, the isolated soil bacterium Acinetobacter lwoffii (RJB-2) (Banerjee et al., 2011) exhibit minimum inhibitory concentrations (MIC) of 125 mM (i.e. 9365.25 mg L 1/9365.25 mg kg 1) of arsenate [As(V)] and 50 mM (3746.1 mg L 1/3746.1 mg kg 1) of arsenite [As(III)]. Arsenic detoxification mechanisms in bacterial cells are responsible for these (Kitja et al., 2009, Srivastava et al., 2012). The mechanisms that have evolved in bacteria for resisting or detoxifying metals can be classified as sequestration, exclusion, efflux, bioaccumulation, enzymatic action and reduction (Silver and Phung, 1996, Srivastava et al., 2012). Microbial arsenic detoxification mechanisms include As(V) uptake in the form of phosphate by phosphate transporters, As(III) uptake in the form of arsenite by aquaglyceroporins (Banerjee et al., 2016, Satyapal et al., 2016). There is an important role of the “Ars” operon in arsenic detoxification in bacterial cells (Srivastava et al., 2012). The product of the arsC gene in “Ars” operon i.e. a cytoplasmic arsenate reductase, catalyzes the reduction of As(V) to As(III). Some bacteria can perform oxidation and methylation of As(III) by arsenite oxidase and methyltransferase respectively. They can also extrude or sequester As(III). In this way, the arsenic-tolerant rhizospheric microbes present in soil can remediate arsenic toxin and simultaneously stop plant arsenic uptake.

The aim of the present study was to determine the effects of inoculation of arsenic resistant bacterial strain Acinetobacter lwoffii (RJB-2) on the growth promotion and yield of mung bean plants (Vigna radiata) under arsenic stressed condition and to investigate the extent of arsenic uptake and its distribution in various plant parts.

Section snippets

Isolation and characterization of bacterial strain from arsenic contaminated soil

The bacterium RJB-2 (Acinetobacter lwoffii) was isolated from the soil samples collected from the arsenic contaminated region of village Chakdah, North 24 Parganas, West Bengal, India (Banerjee et al., 2011). RJB-2 was screened for arsenic resistance assay. 16 s rRNA sequencing of RJB-2 (Acinetobacter lwoffii) was already performed by Banerjee et al., 2011. The strain possesses minimum inhibitory concentrations of 125 mM (i.e. 9365.25 mg L 1/9365.25 mg kg 1) of arsenate [As(V)] and 50 mM (3746.1 mg L 1

Morphological characteristics and numbers of plants per pot of mung bean plants

Significant decrements in morphological aspects, as well as numbers of plants per pot of mung bean plants, had been observed when grown in arsenic-contaminated [22.5 mg kg 1of Na2HAsO7H2O i.e. 5.4 mg kg 1 of As(V)] soil (CCAs) (Figs. 2a, b, 3). The root length, shoot length (Fig. 2a), plant fresh weight, dry stem weight and plant biomass in presence of arsenic [22.5 mg kg 1 of Na2HAsO4·7H2O] were compared with those obtained from CBAs (Fig. 3). When the bacterial strain RJB-2 was treated in the

Conclusions

The results of the present study clearly indicated that the inoculated bacterium RJB-2 (Acinetobacter lwoffii) was highly efficient in protecting the crop plant (Vigna radiata) against the toxic effects of arsenic. Moreover, the isolated bacterium was highly arsenic tolerant and produced plant growth promoting substances like IAA, exopolysaccharide (EPS), and siderophores and also showed phosphate solubilization activity in the absence and even in the presence of high concentration of As(V) [up

Acknowledgements

The authors are thankful to DBT IPLS (Department of Biochemistry, Ballygunge Science College)-University of Calcutta, Kolkata, West Bengal, India for providing Confocal microscopic facilities. The authors are also thankful to Mr. Prothyush Sengupta, Centre for Research in Nanoscience and Nanotechnology, Calcutta University, Kolkata, India and Mr. Krishnendu Paramanik, CIT, Howrah, West Bengal, India for performing SEM imaging studies and for helping in conductivity measurement studies

References (87)

  • P. Jankong et al.

    Enhanced phytoremediation of arsenic contaminated land

    Chemosphere

    (2007)
  • C.Y. Jiang et al.

    Isolation and characterization of a heavy metal-resistant Burkholderia sp. from heavy metal-contaminated paddy field soil and its potential in promoting plant growth and heavy metal accumulation in metal-polluted soil

    Chemosphere

    (2008)
  • K.V. Kumar et al.

    Influence of plant growth promoting bacteria and its mutant on heavy metal toxicity in Brassica juncea grown in fly ash amended soil

    Chemosphere

    (2008)
  • W.-X. Li et al.

    Effect of arsenic on chloroplast ultrastructure and calcium distribution in arsenic hyperaccumulator Pteris vittata L

    Chemosphere

    (2006)
  • S. Lutts et al.

    NaCl-induced senescence in leaves of rice (Oryza sativa L.) cultivars differing in salinity resistance

    Ann. Bot.

    (1996)
  • Y. Ma et al.

    Plant growth promoting rhizobacteria and endophytes accelerate phytoremediation of metalliferous soils

    Biotechnol. Adv.

    (2011)
  • I. Mallick et al.

    Effective rhizoinoculation and biofilm formation by arsenic immobilizing halophilic plant growth promoting bacteria (PGPB) isolated from mangrove rhizosphere: a step towards arsenic rhizoremediation

    Sci. Total Environ.

    (2018)
  • A.A. Meharg

    Arsenic in rice – understanding a new disaster for south-east Asia

    Trends Plant Sci.

    (2004)
  • J. Mesa et al.

    Moving closer towards restoration of contaminated estuaries: bioaugmentation with autochthonous rhizobacteria improves metal rhizoaccumulation in native Spartina maritime

    J. Hazard. Mater.

    (2015)
  • K.A. Mir et al.

    Extraction and speciation of arsenic in plants grown on arsenic contaminated soils

    Talanta

    (2007)
  • M.M. Rahman et al.

    Status of groundwater arsenic contamination in all 17 blocks of Nadia district in the state of West Bengal, India: a 23-year study report

    J. Hydrol.

    (2014)
  • A. Raj et al.

    Metabolic adaptation of Pteris vittata L. gametophyte to arsenic induced oxidative stress

    Bioresour. Technol.

    (2011)
  • M. Rajkumar et al.

    Effects of inoculation of plant-growth promoting bacteria on Ni uptake by Indian mustard

    Bioresour. Technol.

    (2008)
  • M. Rajkumar et al.

    Endophytic bacteria and their potential to enhance phytoextraction

    Chemosphere

    (2009)
  • M. Rajkumar et al.

    Potential of siderophore producing bacteria for improving heavy metal phytoextraction

    Trends Biotechnol.

    (2010)
  • J.M. Rosas-Castor et al.

    Evaluation of the transfer of soil arsenic to maize crops in suburban areas of San Luis Potosi, Mexico

    Sci. Total Environ.

    (2014)
  • A. Sharma et al.

    Plant growth-promoting bacterium Pseudomonas sp. strain GRP3 influences iron acquisition in mung bean (Vigna radiata L. Wilzeck)

    Soil Biol. Biochem.

    (2003)
  • X.-F. Sheng et al.

    Characterization of heavy metal-resistant endophytic bacteria from rape (Brassica napus) roots and their potential in promoting the growth and lead accumulation of rape

    Environ. Pollut.

    (2008)
  • M. Shri et al.

    Effect of arsenic on growth, oxidative stress, and antioxidant system in rice seedlings

    Ecotoxicol. Environ. Saf.

    (2009)
  • N. Singh et al.

    Arsenic speciation and arsenic and phosphate distribution in arsenic hyperaccumulator Pteris vittata L. and nonhyperaccumulator Pteris ensiformis L

    Environ. Pollut.

    (2006)
  • N. Singh et al.

    Metabolic adaptations to arsenic-induced oxidative stress in Pteris vittata L. and Pteris ensiformis L

    Plant Sci.

    (2006)
  • N. Singh et al.

    Arsenic accumulation pattern in 12 Indian ferns and assessing the potential of Adiantum capillusveneris, in comparison to Pteris vittata, as arsenic hyperaccumulator

    Bioresour. Technol.

    (2010)
  • S. Srivastava et al.

    Mitigation approach of arsenic toxicity in chickpea grown in arsenic amended soil with arsenic tolerant plant growth promoting Acinetobacter sp

    Ecol. Eng.

    (2014)
  • S. Srivastava et al.

    Influence of inoculation of arsenic-resistant Staphylococcus arlettae on growth and arsenic uptake in Brassica juncea (L.) Czern.Var. R-46

    J. Hazard. Mater.

    (2013)
  • S. Tu et al.

    Interactive effects of pH, arsenic and phosphorus on uptake of As and P and growth of the arsenic hyperaccumulator Pteris vittata L., under hydroponic conditions

    Environ. Exp. Bot.

    (2003)
  • C. Tu et al.

    Effects of arsenic on concentration and distribution of nutrients in the fronds of the arsenic hyperaccumulator Pteris vittata L

    Environ. Pollut.

    (2005)
  • J.-Y. Xu et al.

    Arsenic enhanced plant growth and altered rhizosphere characteristics of hyperaccumulator Pteris vittata

    Environ. Pollut.

    (2014)
  • M.J. Abedin et al.

    Arsenic uptake and accumulation in rice (Oryza sativa L.) irrigated with contaminated water

    Plant Soil

    (2002)
  • M. Bajji et al.

    The use of the electrolyte leakage method for assessing cell membrane stability as a water stress tolerance test in durum wheat

    Plant Growth Regul.

    (2002)
  • S. Banerjee et al.

    Arsenic accumulating and transforming bacteria isolated from contaminated soil for potential use in bioremediation

    J. Environ. Sci. Health A Tox. Hazard. Subst. Environ. Eng.

    (2011)
  • A. Banerjee et al.

    Statistical design of experiments for optimization of arsenate reductase production by Kocuria palustris (RJB-6) and immobilization parameters in polymer beads

    RSC Adv.

    (2016)
  • C.A. Bomfeti et al.

    Exopolysaccharides produced by the symbiotic nitrogen-fixing bacteria of leguminosae

    Rev. Bras. Cienc. Solo.

    (2011)
  • A. Carbonell-Barrachina et al.

    Arsenic uptake, distribution, and accumulation in tomato plants: effects of arsenite on plant growth and yield

    J. Plant Nutr.

    (1995)
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