Date Published: August 17, 2016
Publisher: Springer Berlin Heidelberg
Author(s): Muniswamy David, Paidi Murali Krishna, Jeybalan Sangeetha.
Metal bioaccessibility is an alarming issue in croplands of mining sites due to overloading of toxic metals. Hence, the present study is aimed to determine the overloading of toxic metal in croplands across the Tawag village, Hutti, Raichur, India. Correspondingly, to identify the soil bacterial growth, physiological oxidative stress enzyme activity and surface macromolecular functional group evolution were analysed in and around the toxic metal contaminated sites through FT-IR and FT-Raman spectrometry. The evaluated results attribute that the study area is heavily polluted with the toxic metals such as arsenic, cadmium, chromium, lead and zinc. However, biochemical and 16S rRNA gene sequence homology tree confirmed that the arsenic and cadmium-resistant isolate belongs to Bacillus sp. MDPMK-02 and retrieved unique Gene Bank ID KT596811 (accession number) at National Centre for Biotechnology information (NCBI), India. Additionally, sodium arsenite-amended culture media possessing reduced biomass and enhanced the activity of oxidative stress defence enzymes such as superoxide dismutase (SOD) and catalase (CAT) than cadmium chloride-amended medium and control. Subsequently, the infrared (IR) and Raman spectral analytical assessment distinguish that arsenic-treated Gram-positive isolate membrane fetched high percentage of hydration, elevation of surface polysaccharides, proteins and polyhydroxybutyric acid (PHBA) molecular specific stretch intensity compared to cadmium exposures. From these results, the study concluded that the mining wastes significantly pollute the surrounding croplands, and also Bacillus sp. MDPMK-02 possesses good chemosensing for cross-protection and bio-adaptation of toxic metal ions. Hence, these isolates can be compiled and implemented in environmental hazardous management techniques such as bioremediation, bioleaching and biodegradation.
Nowadays accumulation of toxic metals through dumping of ore tailings and leachate overflow in and around mining environment is raising the alarm on ecological stress. The mining activities, especially in open-pit mining, typically generate the highest quantities of solid wastes in the form of waste rock and tailings (Mingliang and Haixia 2009). The discharge of acidic mine drainage (AMD) with elevated levels of heavy metals can contaminate the downstream water, agricultural soils, food crops, biota and pose a health risk to residents near the mining areas (Duruibe et al. 2007; Tian et al. 2009; Plumlee and Morman 2011). Heavy metal contamination by mining is a major environmental concern on a global scale, particularly in developing countries (Zhuang et al. 2014). Moreover, cadmium is relatively a typical element not found in the pure state in nature. Its principal uses include protective plating for steel, stabilizers for polyvinyl chloride pigments in plastics and glasses, electrode material in nickel–cadmium batteries and as a component of various alloys and ceramics (Govil et al. 2008). Mine drainage water, waste water from the processing of ore and rainwater run-off from the general ore tailing area and improper disposal of trace elements from industrial wastes ultimately leads to toxic metal especially cadmium pollution (Arhin et al. 2015).
The present geochemical status results attribute that study area Tawag village polluted by toxic metals such as arsenic, cadmium, copper, lead and zinc. Correspondingly, indigenous metal-resistant isolate bacteria Bacillus sp. MDPMK-02 possess good growth and physiological stress flexibility. Nevertheless, the IR spectral and FT-Raman surface scattering vibrational spectrum enlighten about the Gram-positive bacteria enhancing the surface polarity for metal bio-absorbance and chemotactic sensing for environmental changes. These results prove that Bacillus sp. MDPMK-02 could be considered and used in bioleaching, bioremediation and biodegradation of mining and industrial waste treatment.