Anamika Kushwaha | Motilal Nehru National Institute of Technology (original) (raw)

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Papers by Anamika Kushwaha

Lead accumulation in soils is of serious concern in agricultural production due to the harmful ef... more Lead accumulation in soils is of serious concern in agricultural production due to the harmful effects on soil
microflora, crop growth and food safety. In soil, speciation of lead greatly affects its bioavailability and thus its
toxicity on plants and microbes. Many plants and bacteria have evolved to develop detoxification mechanisms to
counter the toxic effect of lead. Factors influencing the lead speciation include soil pH, organic matter, presence
of various amendments, clay minerals and presence of organic colloids and iron oxides. Unlike, other metals
little is known about the speciation and mobility of lead in soil. This review focuses on the speciation of lead in
soil, its mobility, toxicity, uptake and detoxification mechanisms in plants and bacteria and bioremediation
strategies for remediation of lead contaminated repositories.

A lead resistant bacterial strain was isolated from coal mine dump and identified as Acinetobacte... more A lead resistant bacterial strain was isolated from coal mine dump and identified as Acinetobacter junii Pb1 on basis of 16S rRNA gene sequencing. The minimum inhibitory concentration of lead for the strain was 16000 mg l-1 and it showed antibiotic and multi metal resistance. In aqueous culture, at an initial lead [Pb(II)] concentration of 100 and 500 mg l-1, lead adsorption and accumulation by the isolate was 100% and 60%, at pH 7 at 30°C after 48 and 120 hours, respectively. The two fractions of exopolysaccharide (EPS), loosely associated EPS (laEPS) and bound EPS (bEPS), and whole cells (devoid of EPS) showed high binding affinity towards Pb(II). The binding affinity of laEPS towards Pb(II) (1071 mg Pb g-1) was 3 times higher than that of bEPS (321.5 mg Pb g-1) and 6.5 times higher than that of whole cells (165 mg Pb g-1). The binding affinity of EPS and whole cells with Pb(II), reported in the current study is considerably higher as compared to that reported in literature, till date. SEM analysis, showed an increase in thickness of cells on exposure to Pb(II) and TEM analysis, revealed its accumulation (interior of cell) and its adsorption (with the external cell surface). The isolate was also found to be positive for indole acetic acid (IAA) and 1-aminocyclopropane-1-carboxylate (ACC) deaminase production which helps in promoting plant growth. Thus, this study provides a new understanding towards Pb(II) uptake by A. junii Pb1, highlighting its potential on the restoration of Pb(II) contaminated repositories.

Heavy metals, such as cobalt, copper, manganese, molybdenum, and zinc, are essential in trace amo... more Heavy metals, such as cobalt, copper, manganese, molybdenum, and zinc, are essential in trace amounts for growth by plants and other living organisms. However, in excessive amounts these heavy metals have deleterious effects. Like other organisms, plants possess a variety of detoxification mechanisms to counter the harmful effects of heavy metals. These include the restriction of heavy metals by mycorrhizal association, binding with plant cell wall and root excretions, metal efflux from the plasma membrane, metal chelation by phytochelatins and metallothioneins, and compartmentalization within the vacuole. Phytoremediation is an emerging technology that uses plants and their associated rhizospheric microorganisms to remove pollutants from contaminated sites. This technology is inexpensive, efficient, and ecofriendly. This review focuses on potential cellular and molecular adaptations by plants that are necessary to tolerate heavy metal stress.

Book Reviews by Anamika Kushwaha

Although some heavy metals such as cobalt, copper, manganese, molybdenum, and zinc etc. are essen... more Although some heavy metals such as cobalt, copper, manganese, molybdenum, and zinc etc. are essential trace elements, most of them can be toxic to all forms of life, including microorganisms, when present at high concentration due to the formation of complex compounds within the cell. Since heavy metals cannot be biodegraded they persist in environment and cause pollution of air, water, and soils. Thus, the main strategies to control heavy metal pollution are to reduce its bioavailability, mobility, and toxicity of heavy metals. Methods which are incorporated for remediation of heavy metal-contaminated environment include physical removal, detoxification, bioleaching, and phytoremediation. Due to introduction of heavy metals both by natural and industrial processes heavy metals are increasingly found in microbial habitats thus microbes have evolved several mechanisms to tolerate and detoxify the heavy metals. These include: change in redox potential, production of metal-binding peptides and proteins (e.g., metallothioneins), organic and inorganic precipitation, active transport, efflux and intracellular compartmentalization, while cell walls and other structural components have significant metal-binding abilities. The microbial communities that is present in metal-contaminated environment they have unique forms of respiration and these microbes are able to reduce heavy metals in order to remediate metal-contaminated sites. This chapter focuses on potential mechanisms adapted by microbes that are necessary to tolerate the heavy metal stress.