DNA gyrase, a typical type II topoisomerase that can introduce negative supercoils in DNA, is essential for replication and transcription in prokaryotes. The apicomplexan parasite Plasmodium falciparum contains the genes for both gyrase A and gyrase B in its genome. Due to the large sizes of both proteins and the unusual codon usage of the highly AT-rich P. falciparum gyrA (PfgyrA) and PfgyrB genes, it has so far been impossible to characterize these proteins, which could be excellent drug targets. Here, we report the cloning, expression, and functional characterization of full-length PfGyrB and functional domains of PfGyrA. Unlike Escherichia coli GyrB, PfGyrB shows strong intrinsic ATPase activity and follows a linear pattern of ATP hydrolysis characteristic of dimer formation in the absence of ATP analogues. These unique features have not been reported for any known gyrase so far. The PfgyrB gene complemented the E. coli gyrase temperature-sensitive strain, and, together with the N-terminal domain of PfGyrA, it showed typical DNA cleavage activity. Furthermore, PfGyrA contains a unique leucine heptad repeat that might be responsible for dimerization. These results confirm the presence of DNA gyrase in eukaryotes and confer great potential for drug development and organelle DNA replication in the deadliest human malarial parasite, P. falciparum.DNA topoisomerases are a special class of enzymes that promote the interconversions of various topological forms of DNA that are generated during DNA replication, transcription, recombination, or related processes (8, 12). These enzymes are grouped mainly into two classes, namely, type I and type II, based on their ability to break one or both strands of DNA. Type II enzymes are further divided into A and B subclasses. The archaeon Sulfolobus shibatae contains structurally distinct type IIB topoisomerases (8). Eukaryotic type IIA topoisomerases form homodimers, whereas bacterial type IIA enzymes form heterotetramers comprised of two subunits of A and B polypeptides each (8).The DNA gyrase falls into the type IIA category, and it is responsible for catalyzing ATP-dependent DNA supercoiling activity in prokaryotes (22, 31). The best-studied gyrase so far is from Escherichia coli, which forms an A 2 B 2 complex. The GyrA N-terminal domain contains the DNA breakage and union domain, while the C-terminal domain shows DNA wrapping activity (41, 42). The GyrB N-terminal domain has an ATPase function, whereas the C-terminal domain binds to DNA and probably interacts with GyrA (6, 9, 21). These enzymes are excellent targets for various antibacterial agents including quinolones and coumarins (1,16,32,33).Although gyrase is commonly found in prokaryotes, there are a few recent reports of the existence of bacterium-type gyrases in plants that might be important for organellar DNA replication and transcription. It has been shown that Arabidopsis thaliana DNA gyrase is targeted to the chloroplast and mitochondria and that both subunits are essential for growth (51).Similar to Arabido...

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Heavy metal and pesticide pollution have become an inevitable part of the modern industrialized environment that find their way into all ecosystems. Because of their persistent nature, recalcitrance, high toxicity and biological enrichment, metal and pesticide pollution has threatened the stability of the environment as well as the health of living beings. Due to the environmental persistence of heavy metals and pesticides, they get accumulated in the environs and consequently lead to food chain contamination. Therefore, remediation of heavy metals and pesticide contaminations needs to be addressed as a high priority. Various physico-chemical approaches have been employed for this purpose, but they have significant drawbacks such as high expenses, high labor, alteration in soil properties, disruption of native soil microflora and generation of toxic by-products. Researchers worldwide are focusing on bioremediation strategies to overcome this multifaceted problem, i.e., the removal, immobilization and detoxification of pesticides and heavy metals, in the most efficient and cost-effective ways. For a period of millions of evolutionary years, microorganisms have become resistant to intoxicants and have developed the capability to remediate heavy metal ions and pesticides, and as a result, they have helped in the restoration of the natural state of degraded environs with long term environmental benefits. Keeping in view the environmental and health concerns imposed by heavy metals and pesticides in our society, we aimed to present a generalized picture of the bioremediation capacity of microorganisms. We explore the use of bacteria, fungi, algae and genetically engineered microbes for the remediation of both metals and pesticides. This review summarizes the major detoxification pathways and bioremediation technologies; in addition to that, a brief account is given of molecular approaches such as systemic biology, gene editing and omics that have enhanced the bioremediation process and widened its microbiological techniques toward the remediation of heavy metals and pesticides.

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