Available Approaches of Remediation and Stabilisation of Metal Contamination in Soil: A Review

Anthropogenic activities, such as mining of natural resources, manufac-turing industries, modern agricultural practices and energy production have resulted in the release of heavy metals with resultant harmful im-pacts in some natural environments. Toxic heavy metals are harmful to living organisms even at low concentrations. Therefore, heavy metal contaminated sites should be remediated as heavy metals do not decompose into less harmful substances and are retained in the soil. Conventional methods are used for remediation of heavy metal contaminated soils such as heavy metal extraction, immobilization and removal of soils to landfill produce large quantities of toxic products including insoluble hydroxides and are rarely cost effective. The advent of bioremediation technologies like biosparging, bioventing and bioaugmentation has provided an alternative to conventional methods for remediating heavy metal contaminated soils. A subset of bacteria found in the rhizosphere has been found to increase the tolerance of plants to heavy metals in soil. These bacteria commonly known as plant growth promoting rhizobacteria or Plant Growth Promoting Rhizobacteria (PGPR) are showing promise as a bioremediation technique for the stabilisation and remediation of heavy metal contami-nated sites. PGPR can improve plant growth via a variety of mechanism including fixing atmospheric N to improve N status and making plants more tolerant of heavy metals. Scattered literature is harnessed to review the principles, advantages and disadvantages of the available technologies for remediating heavy metal contaminated soils and is presented.

<i>Citrobacter rodentium</i>, a Gut Pathogen: The Yin and the Yang of Its Pathophysiology, Immunity and Clinical Manifestation in Mice

Pathogenic strains of E. coli including enteropathogenic E. coli (EPEC), enterohemorrhagic E. coli (EHEC), enterotoxigenic E. coli (ETEC) are principle causes for diarrhoea in many parts of the globe. Citrobacter rodentium (C. rodentium), a gram negative bacterium, is a murine pathogen that also utilizes type III secretion system and similar virulence factors to EPEC and EHEC and forms comparable attaching/effacing lesions in the intestines as EPEC and EHEC. The infection caused by C. rodentium in mice is usually self-limiting and results in only minor systemic effects with higher mortality in some susceptible mouse strains. All these characteristics have made the bacteria a commonly used model to study host immune responses to pathogenic E. coli infection. In this review, we focus on the impact of virulence factors of the pathogen;different immune components involved in the immune response and summarize their role during C. rodentium infection.

Dissecting Emerging Aspects of Regulatory Circuitry in Man and Mice: Regulatory T Cell Biology

Regulatory T cells (Treg), a component of adaptive immunity, are well known for their immunosuppressive roles and their ability to maintain the balance between the immunological and pathological reactions. Treg have been shown to provide protective responses and their depletion has resulted severe pathology in some pathogen infections. The work presented here has unravelled the potential of regulatory cells in the immune system including different repertoir of Treg cell subsets, markers to distinguish them, Treg suppression mechanisms in the pathogenesis of various infections and summarize different mouse models depleting Tregs. These findings would help set up future avenues of research to elucidate a key mechanism of action of these cells and provide new therapeutic insights for pathogenesis and also for broader antibacterial/antiviral/antiproliferative immunity.