Mudsser Azam

Heavy Metals and Human Health: Mechanistic Insight into Toxicity and Counter Defense System of Antioxidants

Heavy metals, which have widespread environmental distribution and originate from natural and anthropogenic sources, are common environmental pollutants. In recent decades, their contamination has increased dramatically because of continuous discharge in sewage and untreated industrial effluents. Because they are non-degradable, they persist in the environment; accordingly, they have received a great deal of attention owing to their potential health and environmental risks. Although the toxic effects of metals depend on the forms and routes of exposure, interruptions of intracellular homeostasis include damage to lipids, proteins, enzymes and DNA via the production of free radicals. Following exposure to heavy metals, their metabolism and subsequent excretion from the body depends on the presence of antioxidants (glutathione, α-tocopherol, ascorbate, etc.) associated with the quenching of free radicals by suspending the activity of enzymes (catalase, peroxidase, and superoxide dismutase). Therefore, this review was written to provide a deep understanding of the mechanisms involved in eliciting their toxicity in order to highlight the necessity for development of strategies to decrease exposure to these metals, as well as to identify substances that contribute significantly to overcome their hazardous effects within the body of living organisms.

Antimicrobial and fluorescence finishing of woolen yarn with Terminalia arjuna natural dye as an ecofriendly substitute to synthetic antibacterial agents

The current study deals with the use of Terminalia arjuna natural dye as an ecofriendly finishing agent for producing highly functional antimicrobial and fluorescent woolen yarn along with the evaluation of kinetic and thermodynamic adsorption characteristics. The effect of pH on the adsorption was investigated, showing an increase in adsorption capacity with decreasing pH over the range of 2–9, with maximum adsorption at pH 3.5. Two kinetic equations pseudo-first order and pseudo-second order were employed for determining adsorption rates. The pseudo-second order equation provided the best fit to experimental data with an activation energy of 105.58 kJ mol−1, indicating chemisorption. The equilibrium adsorption data was fitted to Langmuir, Freundlich and Redlich–Peterson adsorption isotherms. The adsorption behavior accorded with the Redlich–Peterson isotherm with exceptionally high regression coefficients for dyeing temperatures of 50, 70 and 90 °C with dye concentration varying from 0.5–10% (o.w.f). Comparative results of the colorimetric properties (CIEL*a*b* and K/S) using a spectrophotometer under D65 illuminant (10° standard observer) and color fastness (light, wash, and rub) of dyed woolen yarns were studied to quantify the effect of metal mordants. The antimicrobial potential of Terminalia arjuna solution and dyed woolen yarn were assessed in terms of percentage inhibition of bacterial growth against a wide variety of bacterial strains, showing more than 85% inhibition. Reduction in antimicrobial activity of dyed woolen yarn was observed with mordanted samples, however they were found to retain more antimicrobial activity as compared to unmordanted samples as a function of successive washing cycles. The chemical nature of different mordants and wool–mordant–dye complex forming ability were found to have significant impact on the colorimetric and fluorescence characteristics of dyed woolen yarn.

Novel approaches of beneficial Pseudomonas in mitigation of plant diseases – an appraisal

Control of plant diseases has always remained a challenge as diseases affecting plant health are a major and chronic threat not only to food production, but also to ecosystem stability worldwide. As agricultural production intensified over the past three decades, producers became dependent on agrochemicals as a relatively reliable method of crop protection. However, growing concerns regarding continued use of agrochemicals, posing adverse effects on human health besides posing the threat of environmental deterioration, has driven search for novel environment friendly methods to control plant diseases that in turn can contribute to the goal of sustainability in agriculture. Mitigation of plant diseases by naturally inhabiting antagonistic micro-organisms such as plant growth-promoting rhizobacteria has gained much importance as biocontrol agents seem to be the best possible measures for saving plants from phytopathogenic organisms without causing any harmful effect to mankind as well as to the environment. Mechanisms of microbial antagonism toward phytopathogenic organisms include competition for nutrients and space, production of siderophores, hydrogen cyanide, antibiotics, and/or production of fungal cell wall-degrading lytic enzymes. The present review is aimed at exploring benefits of natural alternatives for agrochemicals along with the study of their antagonistic mechanisms that makes them a novel substitute to agrochemicals.

blaCTX-M-152, a Novel Variant of CTX-M-group-25, Identified in a Study Performed on the Prevalence of Multidrug Resistance among Natural Inhabitants of River Yamuna, India

Natural environment influenced by anthropogenic activities creates selective pressure for acquisition and spread of resistance genes. In this study, we determined the prevalence of Extended Spectrum β-Lactamases producing gram negative bacteria from the River Yamuna, India, and report the identification and characterization of a novel CTX-M gene variant blaCTX-M-152. Of the total 230 non-duplicate isolates obtained from collected water samples, 40 isolates were found positive for ESBL production through Inhibitor-Potentiation Disc Diffusion test. Based on their resistance profile, 3% were found exhibiting pandrug resistance (PDR), 47% extensively drug resistance (XDR), and remaining 50% showing multidrug resistant (MDR). Following screening and antimicrobial profiling, characterization of ESBLs (blaTEM and blaCTX-M), and mercury tolerance determinants (merP, merT, and merB) were performed. In addition to abundance of blaTEM-116 (57.5%) and blaCTX-M-15 (37.5%), bacteria were also found to harbor other variants of ESBLs like blaCTX-M-71 (5%), blaCTX-M-3 (7.5%), blaCTX-M-32 (2.5%), blaCTX-M-152 (7.5%), blaCTX-M-55 (2.5%), along with some non-ESBLs; blaTEM-1 (25%) and blaOXY (5%). Additionally, co-occurrence of mercury tolerance genes were observed among 40% of isolates. In silico studies of the new variant, blaCTX-M-152were conducted through modeling for the generation of structure followed by docking to determine its catalytic profile. CTX-M-152 was found to be an out-member of CTX-M-group-25 due to Q26H, T154A, G89D, P99S, and D146G substitutions. Five residues Ser70, Asn132, Ser237, Gly238, and Arg273 were found responsible for positioning of cefotaxime into the active site through seven H-bonds with binding energy of -7.6 Kcal/mol. Despite small active site, co-operative interactions of Ser237 and Arg276 were found actively contributing to its high catalytic efficiency. To the best of our knowledge, this is the first report of blaCTX-M-152 of CTX-M-group-25 from Indian subcontinent. Taking a note of bacteria harboring such high proportion of multidrug and mercury resistance determinants, their presence in natural water resources employed for human consumption increases the chances of potential risk to human health. Hence, deeper insights into mechanisms pertaining to resistance development are required to frame out strategies to tackle the situation and prevent acquisition and dissemination of resistance determinants so as to combat the escalating burden of infectious diseases.

Prospects for Exploiting Bacteria for Bioremediation of Metal Pollution

Metals being recalcitrant to biodegradation process pose a persistent threat to human health and environment. In view of increase in discharge along with improper management of persistent metal pollutants, it is imperative to develop cost-effective and efficient methods for their remediation. As contamination of soil and water has threatened the well being of humans and natural environment, microorganisms play crucial role in combating the widespread pollution of global environment. Clusters of genes coding for catabolic transformation facilitate their detoxification from the environment. Development of effective tools to facilitate environmental cleanup of metal pollutants beyond genetic confines of natural host has resulted in the expressional enhancement of promiscuous enzymes, involved in the transformation of metal compounds. A thorough understanding of microbes that express heterologous proteins for metal transformation would result in economic production and as such its application in bioremediation process. This review summarizes fundamental insights regarding metals in relation to oxidative stress, insights on metal binding proteins/peptides for immobilization, information regarding genetic engineering for enzymes involved in metal transformation, and strategies that can be employed to overcome the bottlenecks associated with microbial based remediation strategies.

Nanostructured coordination complexes/polymers derived from cardanol: “one-pot, two-step” solventless synthesis and characterization

Growing interests in the development of advanced functional materials from renewable resources due to the depleting petroleum resources, increasing costs, and associated hazards reflect global requirement for increased sustainability. Cardanol [Col] is an agro by-product of the cashew nut industry. It is cost effective, nontoxic, biodegradable and an abundantly available renewable resource. In the present study, we report the development of nanostructured coordination polymer [CP] self-standing transparent films from Col (as an organic linker or bridging-ligand) and Mn(II) ‘d5’ and Co(II) ‘d7’ divalent metal ions (as metal nodes) by a solid-state in situ method. The resulting CP films showed nanoporous morphology, amorphous behaviour, good thermal stability up to 260–300 °C, moderate antibacterial activity against Staphylococcus aureus (MTCC 902), Escherichia coli (ATCC 25922) and Pseudomonas aeruginosa (MTCC 2453) and also good anti-biofilm activity.

Perspective Insights into Disease Progression, Diagnostics, and Therapeutic Approaches in Alzheimer's Disease: A Judicious Update

Alzheimers disease (AD) is a neurodegenerative disorder characterized by the progressive accumulation of β-amyloid fibrils and abnormal tau proteins in and outside of neurons. Representing a common form of dementia, aggravation of AD with age increases the morbidity rate among the elderly. Although, mutations in the ApoE4 act as potent risk factors for sporadic AD, familial AD arises through malfunctioning of APP, PSEN-1, and−2 genes. AD progresses through accumulation of amyloid plaques (Aβ) and neurofibrillary tangles (NFTs) in brain, which interfere with neuronal communication. Cellular stress that arises through mitochondrial dysfunction, endoplasmic reticulum malfunction, and autophagy contributes significantly to the pathogenesis of AD. With high accuracy in disease diagnostics, Aβ deposition and phosphorylated tau (p-tau) are useful core biomarkers in the cerebrospinal fluid (CSF) of AD patients. Although five drugs are approved for treatment in AD, their failures in achieving complete disease cure has shifted studies toward a series of molecules capable of acting against Aβ and p-tau. Failure of biologics or compounds to cross the blood-brain barrier (BBB) in most cases advocates development of an efficient drug delivery system. Though liposomes and polymeric nanoparticles are widely adopted for drug delivery modules, their use in delivering drugs across the BBB has been overtaken by exosomes, owing to their promising results in reducing disease progression.

Molecular Characterization of Mercury Resistant Bacteria Inhabiting Polluted Water Bodies of Different Geographical Locations in India

Mercury pollution is a major environmental problem that arises as a result of natural processes as well as from anthropogenic sources. In response to toxic mercury compounds, microbes have developed astonishing array of resistance systems to detoxify them. To address this challenge, this study was aimed in screening bacterial isolates for their tolerance against varied concentrations of phenylmercuric acetate. Mercury transformation by bacteria being sensitive to factors such as available carbon source, etc. that affect mer-mediated transformation, screened mercury tolerant bacteria were also studied for their tolerance to different antimicrobials and carbon sources, followed by identification using biochemical as well as 16S rRNA approach. Following identification, gene encoding organomercurial lyase catalyzing protonolytic cleavage of C–Hg bond of organic mercury was amplified using gene specific primers, cloned in pGEMT® easy vector and sequenced. Microbe-based approach using organomercurial lyase encoded by merB gene being potentially economic, provides foundation to facilitate genetic manipulation of this environmentally important enzyme to remove high concentrations of obstinate mercury using holistic, multifaceted approach for use in bioremediation through generation of transgenics or as catalyst for use in bioreactors.

Study of pandrug and heavy metal resistance among E. coli from anthropogenically influenced Delhi stretch of river Yamuna

Escalating burden of antibiotic resistance that has reached new heights present a grave concern to mankind. As the problem is no longer confined to clinics, we hereby report identification of a pandrug resistant Escherichia coli isolate from heavily polluted Delhi stretch of river Yamuna, India. E. coli MRC11 was found sensitive only to tobramycin against 21 antibiotics tested, with minimum inhibitory concentration values >256 μg/mL for amoxicillin, carbenicillin, aztreonam, ceftazidime and cefotaxime. Addition of certain heavy metals at higher concentrations were ineffective in increasing susceptibility of E. coli MRC11 to antibiotics. Withstanding sub-optimal concentration of cefotaxime (10 μg/mL) and mercuric chloride (2 μg/mL), and also resistance to their combinatorial use, indicates better adaptability in heavily polluted environment through clustering and expression of resistance genes. Interestingly, E. coli MRC11 harbours two different variants of blaTEM (blaTEM-116 and blaTEM-1 with and without extended-spectrum activity, respectively), in addition to mer operon (merB, merP and merT) genes. Studies employing conjugation, confirmed localization of blaTEM-116, merP and merT genes on the conjugative plasmid. Understanding potentialities of such isolates will help in determining risk factors attributing pandrug resistance and strengthening strategic development of new and effective antimicrobial agents.

Plant abiotic stress: a prospective strategy of exploiting promoters as alternative to overcome the escalating burden

ABSTRACT Plants being sessile are shaped by evolution to adapt themselves and tolerate various stresses, be it salinity stress, drought, high/low temperature in nature. They have evolved with every alternate strategy to tackle serious abiotic stresses through considerable degree of developmental plasticity, including adaptation via cascades of molecular networks. Understanding the mechanism of genes responsible for plant adaptation to environment will help in predicting the scenarios, expanding the genetic aspect of abiotic stress-regulating genes to protect and extrapolate the level of tolerance or vulnerability conferred in natural ecosystems. Complementing the agronomic need for greater tolerance to abiotic stress, studying plant abiotic stress response can help in gaining insight into plant biology that can be practically applied to unlock the secrets in order to improve plant productivity to feed the ever increasing population of human beings.