Heavy metals are natural constituents of the environment, but indiscriminate use for human purposes has altered their geochemical cycles and biochemical balance. This results in excess release of heavy metals such as cadmium, copper, lead, nickel, zinc etc. into natural resources like the soil and aquatic environments. Prolonged exposure and higher accumulation of such heavy metals can have deleterious health effects on human life and aquatic biota. The role of microorganisms and plants in biotransformation of heavy metals into nontoxic forms is well-documented, and understanding the molecular mechanism of metal accumulation has numerous biotechnological implications for bioremediation of metal-contaminated sites. In view of this, the present review investigates the abilities of microorganisms and plants in terms of tolerance and degradation of heavy metals. Also, advances in bioremediation technologies and strategies to explore these immense and valuable biological resources for bioremediation are discussed. An assessment of the current status of technology deployment and suggestions for future bioremediation research has also been included. Finally, there is a discussion of the genetic and molecular basis of metal tolerance in microbes, with special reference to the genomics of heavy metal accumulator plants and the identification of functional genes involved in tolerance and detoxification.

Agriculture is a multifarious interface between plants and associated microorganisms. In contemporary agriculture, emphasis is being given to environmentally friendly approaches, particularly in developing countries, to enhance sustainability of the system with the least negative effects on produce quality and quantity. Modern agricultural practices such as extensive tillage, the use of harmful agrochemicals, mono-cropping, etc. have been found to influence soil microbial community structure and soil sustainability. On the other hand, the question of feeding the ever-growing global population while ensuring system sustainability largely remains unanswered. Agriculturally important microorganisms are envisaged to play important roles in various measures to raise a healthy and remunerative crop, including integrated nutrient management, as well as disease and pest management to cut down agrochemicals without compromising the agricultural production. These beneficial microorganisms seem to have every potential to provide an alternative opportunity to overcome the ill effects of various components of traditional agriculture being practiced by and large. Despite an increased awareness of the importance of organically produced food, farmers in developing countries still tend to apply inorganic chemical fertilizers and toxic chemical pesticides beyond the recommended doses. Nutrient uptake enhancement, biocontrol of pests and diseases using microbial inoculants may replace/reduce agrochemicals in agricultural production system. The present review aims to examine and discuss the shift in microbial population structure due to current agricultural practices and focuses on the development of a sustainable agricultural system employing the tremendous untapped potential of the microbial world.

Membrane biofouling is widely acknowledged as the most frequent adverse event in wastewater treatment systems resulting in significant loss of treatment efficiency and economy. Different strategies including physical cleaning and use of antimicrobial chemicals or antibiotics have been tried for reducing membrane biofouling. Such traditional practices are aimed to eradicate biofilms or kill the bacteria involved, but the greater efficacy in membrane performance would be achieved by inhibiting biofouling without interfering with bacterial growth. As a result, the search for environmental friendly non-antibiotic antifouling strategies has received much greater attention among scientific community. The use of quorum quenching natural compounds and enzymes will be a potential approach for control of membrane biofouling. This approach has previously proven useful in diseases and membrane biofouling control by triggering the expression of desired phenotypes. In view of this, the present review is provided to give the updated information on quorum quenching compounds and elucidate the significance of quorum sensing inhibition in control of membrane biofouling.

High-quality drinking water is obtained using membrane technology. Biofilm development lowers filtration efficacy and eventually membranes must be replaced. In natural environments, a micro-organism produces different kinds of quorum sensing (QS) molecules resulting in biofilm formation and biofouling. Biological fouling is a major problem in desalination and water purification plants. Biofilm formation can be reduced using eco-friendly substances in the drinking water system based on quorum sensing inhibition (QSI). Vanillin (4-hydroxy-3-methoxybenzaldehyde), a well-known food flavoring agent, was studied for its QSI property against different individual acyl homoserine lactone (AHL) molecules using bio indicator strains. Vanillin showed significant inhibition in short-chain [C4-HSL (69%) and 3-Oxo-C8-HSL (59.8%)] and long-chain AHL molecules. QSI activity was tested on a reverse osmosis (RO) membrane biofilm bacteria Aeromonas hydrophila. Biofilm formation was inhibited up to 46.3% on polystyrene surface. Results suggested that Vanillin could be used as a potential QSI compound that reduces the biofilm formation on RO membranes.