A Review on the Resistance and Accumulation of Heavy Metals by Different Microbial Strains

Heavy metals accumulated the earth crust and causes extreme pollution. Accumulation of rich concentrations of heavy metals in environments can cause various human diseases which risks health and high ecological issues. Mercury, arsenic, lead, silver, cadmium, chromium, etc. are some heavy metals harmful to organisms at even very low concentration. Heavy metal pollution is increasing day by day due to industrialization, urbanization, mining, volcanic eruptions, weathering of rocks, etc. Different microbial strains have developed very efficient and unique mechanisms for tolerating heavy metals in polluted sites with eco-friendly techniques. Heavy metals are group of metals with density more than 5 g/cm3. Microorganisms are generally present in contaminated sites of heavy metals and they develop new strategies which are metabolism dependent or independent to tackle with the adverse effects of heavy metals. Bacteria, Algae, Fungi, Cyanobacteria uses in bioremediation technique and acts a biosorbent. Removal of heavy metal from contaminated sites using microbial strains is cheaper alternative. Mostly species involved in bioremediation include Enterobacter and Pseudomonas species and some of bacillus species too in bacteria. Aspergillus and Penicillin species used in heavy metal resistance in fungi. Various species of the brown algae and Cyanobacteria shows resistance in algae.

Characterization of Cypermethrin-degradation by a Novel Molybdenum-reducing Morganella sp. Isolated from Active Agricultural Land in Northwestern Nigeria

The increasing use of cypermethrin in agricultural fields, household and industrial applications for effective pest control had increased the global burden of the pollutant over the years. Consequently, there is an urgent need to devise techniques to eliminate this pollutant from the environment. A bacterium capable of degrading cypermethrin has been successfully screened and characterized. The bacterium was grown in a mineral salt medium (MSM) supplemented with cypermethrin as its sole carbon and energy source at an optimum pH 7.5, temperature 40 ºC, a carbon source concentration of 4 g/L, optimum incubation time of 24 h and an inoculum size of 400 µL. The potential of Morganella sp. to degrade cypermethrin makes it an important instrument for the degradation of cypermethrin. This knowledge may be useful for the optimization of environmental conditions for cypermethrin bioremediation and important for detoxification of cypermethrin polluted sites.

AIR POLLUTION TOLERANCE INDEX OF WHEAT AND RICE IN THE PROXIMITY OF GAS BASED POWER PLANT

The study aimed to identify the tolerance level of rice and wheat due to air pollutants around the gas-based power plant. Ten sites were selected around 10km radius of gas based power plant. Major air pollutants like NOx, SOx, ozone, and PM10 were monitored in ten sites during the growth of rice and wheat. The Air Quality Index (AQI) of villages falls mostly in the category of moderately polluted sites. Air Pollution Tolerance Index (APTI) is a tool applied for categorizing sensitive or tolerant plants towards air pollution and is calculated by using four biochemical parameters like total chlorophyll content, ascorbic acid, pH, and relative water content of rice and wheat. Results indicated that the pH of cell sap of both the crops was acidic to neutral pH (3.5-6.9) at polluted sites while neutral to slightly alkaline (7.0-7.9) at less polluted sites. Ascorbic acid content was high at polluted sites since ascorbic acid shows a defense mechanism against air pollution. Chlorophyll content (up to 0.61mg/g) and relative water content have shown a significant decrease at most polluted sites. As per APTI values (APTI<11), both the crops were sensitive to air pollution in the selected area. APTI might be beneficial in the selection of crop species in the polluted area which shows that a higher concentration of air pollutants can damage crops severely. APTI was found to be positively correlated with pH, total chlorophyll content, and relative water content and negatively correlated with ascorbic acid.

IN SITU AND EX SITU BIOREMEDIATION OF HEAVY METALS: THE PRESENT SCENARIO

Enhanced population growth, rapid industrialization, urbanization and hazardous industrial practices have resulted in the development of environmental pollution in the past few decades. Heavy metals are one of those pollutants that are related to environmental and public health concerns based on their toxicity. Effective bioremediation may be accomplished through “ex situ” and “in situ” processes, based on the type and concentration of pollutants, characteristics of the site but is not limited to cost. The recent developments in artificial neural network and microbial gene editing help to improve “in situ” bioremediation of heavy metals from the polluted sites. Multi-omics approaches are adopted for the effective removal of heavy metals by various indigenous microbes. This overview introspects two major bioremediation techniques, their principles, limitations and advantages, and the new aspects of nanobiotechnology, computational biology and DNA technology to improve the scenario.