Arvind Sinha

Interaction and nanotoxic effect of ZnO and Ag nanoparticles on mesophilic and halophilic bacterial cells

The toxicity of two commonly used nanoparticles, silver and zinc oxide on mesophilic and halophilic bacterial cells has been investigated. Enterobacter sp., Marinobacter sp., Bacillus subtilis, halophilic bacterium sp. EMB4, were taken as model systems. The nanotoxicity was more pronounced on Gram negative bacteria. ZnO nanoparticles reduced the growth of Enterobacter sp. by 50%, while 80% reduction was observed in halophilic Marinobacter sp. In case of halophiles, this may be attributed to higher content of negatively charged cardiolipins on their cell surface. Interestingly, bulk ZnO exerted minimal reduction in growth. Ag nanoparticles were similarly cytotoxic. Nanotoxicity towards Gram positive cells was significantly less, possibly due to presence of thicker peptidoglycan layer. The bacterium nanoparticle interactions were probed by electron microscopy and energy dispersive X-ray analysis. The results indicated electrostatic interactions between nanoparticles and cell surface as the primary step towards nanotoxicity, followed by cell morphological changes, increase in membrane permeability and their accumulation in the cytoplasm.

Mercury bioaccumulation and simultaneous nanoparticle synthesis by Enterobacter sp. cells

A mercury resistant strain of Enterobacter sp. is reported. The strain exhibited a novel property of mercury bioaccumulation with simultaneous synthesis of mercury nanoparticles. The culture conditions viz. pH 8.0 and lower concentration of mercury promotes synthesis of uniform sized 2-5 nm, spherical and monodispersed intracellular mercury nanoparticles. The remediated mercury trapped in the form of nanoparticles is unable to vaporize back into the environment thus, overcoming the major drawback of mercury remediation process. The mercury nanoparticles were recoverable. The nanoparticles have been characterized by high resolution transmission electron microscopy, energy dispersive X-ray analysis, powder X-ray diffraction and atomic force microscopy. The strain can be exploited for metal bioaccumulation from environmental effluent and developing a green process for nanoparticles biosynthesis.

Microbial mineralization of struvite: A promising process to overcome phosphate sequestering crisis

Due to extensive exploitation of non-renewable phosphate minerals, their natural reserves will exhaust very soon. This necessitates looking for alternatives and an efficient methodology through which indispensable phosphorus can be harvested back. The current study was undertaken to explore the potential of a metallophilic bacterium Enterobacter sp. EMB19 for the recovery of phosphorus as phosphate rich mineral. A very low phosphate concentration strategy was adopted. The process led to the mineralization of phosphorus as homogeneous struvite crystals. For each gram of Epsom salt added, the cells effectively mineralized about 20% of the salt into struvite. The effect of different inorganic sources, culture profile and plausible mechanism involved in crystal formation was also explored. The synthesized struvite crystals typically possessed a prismatic crystal habit. The characterization and identification of the crystals were done using single crystal X-ray diffraction (SCXRD), powder X-ray diffraction (PXRD), energy dispersive X-ray analysis (EDAX) and fourier transform infrared (FTIR). The thermal characteristics were studied using thermo gravimetric analysis (TGA) and differential scanning calorimetric (DSC) processes. The synthesis of struvite by this bacterium seems to be a promising and viable strategy since it serves dual purpose (i) obtaining phosphorus and nitrogen rich fertilizer and (ii) conservation of natural phosphate reserves. This study is very significant in the sense that the process may be used for harvesting and synthesizing other valuable minerals. Also, it will provide new insights into phosphate biomineralization mechanisms.

Synthesis and characterization of monodispersed orthorhombic manganese oxide nanoparticles produced by Bacillus sp. cells simultaneous to its bioremediation

A heavy metal resistant strain of Bacillus sp. (MTCC10650) is reported. The strain exhibited the property of bioaccumulating manganese, simultaneous to its remediation. The nanoparticles thus formed were characterized and identified using energy dispersive X-ray analysis (EDAX), high resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), powder X-ray diffraction (PXRD) and atomic force microscopy (AFM). When the cells were challenged with manganese, the cells effectively synthesized nanoparticles of average size 4.62±0.14nm. These were mostly spherical and monodispersed. The ex situ enzymatically synthesized nanoparticles exhibited an absorbance maximum at 329nm. These were more discrete, small and uniform, than the manganese oxide nanoparticles recovered after cell sonication. The use of Bacillus sp. cells seems promising and advantageous approach. Since, it serves dual purposes of (i) remediation and (ii) nanoparticle synthesis. Considering the increasing demand of developing environmental friendly and cost effective technologies for nanoparticle synthesis, these cells can be exploited for the remediation of manganese from the environment in conjunction with development of a greener process for the controlled synthesis of manganese oxide nanoparticles.

Biochemical Basis of Mercury Remediation and Bioaccumulation by Enterobacter sp. EMB21

The aims of this study were to isolate metal bioaccumulating bacterial strains and to study their applications in removal of environmental problematic heavy metals like mercury. Five bacterial strains belonging to genera Enterobacter, Bacillus, and Pseudomonas were isolated from oil-spilled soil. Among these, one of the strains Enterobacter sp. EMB21 showed mercury bioaccumulation inside the cells simultaneous to its bioremediation. The bioaccumulation of remediated mercury was confirmed by transmission electron microscopy and energy dispersive X-ray. The mercury-resistant loci in the Enterobacter sp. EMB21 cells were plasmid-mediated as confirmed by transformation of mercury-sensitive Escherichia coli DH5α by Enterobacter sp. EMB21 plasmid. Effect of different culture parameters viz-a-viz inoculum size, pH, carbon, and nitrogen source revealed that alkaline pH and presence of dextrose and yeast extract favored better remediation. The results indicated the usefulness of Enterobacter sp. EMB21 for the effective remediation of mercury in bioaccumulated form. The Enterobacter sp. EMB21 seems promising for heavy metal remediation wherein the remediated metal can be trapped inside the cells. The process can further be developed for the synthesis of valuable high-end functional alloy, nanoparticles, or metal conjugates from the metal being remediated.

Antecedents of Crime and Suggested Punishment

Abstract The study assessed the effects of character, professional status, and intentions of a criminal on the magnitude of suggested punishment in a hypothetical experimental setting. The sample was composed of 120 male Indian undergraduates. The analysis yielded a significant main effect of intentions as well as interaction effects of Intentions × Character and of Intentions × Character × Status Factor. The results lend support to cognitive dissonance and attribution theories.

The Effects of Benefactor and Beneficiary Characteristics on Helping Behavior

Abstract This study assessed the effects of perceived need and nearness of the beneficiary and the chronological maturity of the benefactor on helping behavior. The relationship between verbal and objective measures of helping behavior, and the relationship between available resources and helping behavior were also explored. Indian undergraduates (N = 80 men) composed the sample. The results showed that greater perceived need and nearness of the beneficiary, as well as lesser chronological maturity of the benefactor, led to extending greater help. Verbal and objective measures of help did not generally correspond; however, the relationship between verbal and objective measures was modified by the perceived need and nearness of the beneficiary. Resource availability did not have any direct bearing on helping behavior.

Heavy Metal Bioremediation and Nanoparticle Synthesis by Metallophiles

Metallophiles are a group of extremophiles which are resistant to high concentration of metals. These microbes inherently possess properties that can influence the biomineralization processes by changing the physicochemical behaviour of the surrounding, metal speciation, mobility and toxicity. Metallophiles possess an endogenous ability to exquisitely regulate their physiology to overcome the toxic effect of the external metal environment and hence perceived to be excellent bioresource for different biotechnological applications. Their biotechnological applications in different bioprocesses have been quite promising. Recent studies have shown that in combination with bioremediation and biomineralization, these metallophiles can be harnessed to convert environmentally problematic metals into ‘high-end’ important and functional metallic materials. The current chapter describes some of the novel metallophilic microbes and their potential usages in bioremediation of problematic heavy metals from the environment and nanoparticle synthesis. The current level of understanding about metal–microbe interaction and plausible mechanism of metal bioremediation and nanoparticle biosynthesis have also been comprehended in this chapter.