Bioremediation Mechanisms Research Articles

Proteomics and metabolomics: The molecular make‐up of toxic aromatic pollutant bioremediation

Microbial-mediated attenuation of toxic aromatic pollutants offers great potential for the restoration of contaminated environments in an ecologically acceptable manner. However, incomplete biological information regarding the regulation of growth and metabolism in many microbial communities restricts progress in the site-specific mineralization process. In the postgenomic era, recent advances in MS have allowed enormous progress in proteomics and elucidated many complex biological interactions. These research forefronts are now expanding toward the analysis of low-molecular-weight primary and secondary metabolites analysis, i.e., metabolomics. The advent of 2-DE in conjunction with MS offers a promising approach to address the molecular mechanisms of bioremediation. The two fields of proteomics and metabolomics have thus far worked separately to identify proteins and primary and secondary metabolites during bioremediation. A simultaneous study combining functional proteomics and metabolomics, i.e., proteometabolomics would create a system-wide approach to studying site-specific microorganisms during active mineralization processes. This article deals with advances in environmental proteomics and metabolomics and advocates the simultaneous study of both technologies to implement cell-free bioremediation.

Chromium(III) and (VI) tolerance and bioaccumulation in yeast: a survey of cellular chromium content in selected strains of representative genera

Fifty-one wild type, naturally occurring yeast strains belonging to various systematic groups were screened for chromium(III) and (VI) uptake at growth-inhibitory concentrations of the metal. Yeast cells were supplemented with Cr at the moment of inoculation with 0.03 mg d.w. biomass/ml and then cultivated for 3 days in optimal growth media. The tolerance to Cr varied depending on the strain tested and the yeast cultures proved to be generally more sensitive to Cr(VI) (concentration range: 0.1–0.5 mM) than to Cr(III) (0.25–5 mM). The levels of cellular Cr content ranged from 0.29 to 11.10 mg/g d.w. and 0.21–3.3 mg/g d.w. for Cr(III) and Cr(VI), respectively. Distribution diagrams of the cell-accumulated Cr were constructed for the tested strain population, and the general uptake tendency of middle-range amounts of Cr(III), and low-range levels of Cr(VI) was revealed. The cell-accumulated Cr levels were similar at identical, non-toxic concentrations of either Cr form supplemented to the medium. Electron microscopic images proved that cytoplasm and cellular organelles were the ultimate targets for accumulation of both valences of the metal. The extreme cases of the strains revealing either the lowest or the highest Cr tolerance and uptake capabilities are discussed in terms of possible bioremediation mechanisms. The applicability of the strains in both environmental and nutritional practice was also considered.

Use of Thermophilic Bacteria for Bioremediation of Petroleum Contaminants

Several strains of thermophilic bacteria were isolated from the environment of the United Arab Emirates. These bacteria show extraordinary resistance to heat and have their maximum growth rate around 60 80 C. This article investigates the potential of using these facultative bacteria for both in situ and ex situ bioremediation of petroleum contaminants. In a series of batch experiments, bacterial growth was observed using a computer image analyzer following a recently developed technique. These experiments showed clearly that the growth rate is enhanced in the presence of crude oil. This is coupled with a rapid degradation of the crude oil. These bacteria were found to be ideal for breaking down long-chain organic molecules at a temperature of 40 C, which is the typical ambient temperature of the Persian Gulf region. The same strains of bacteria are also capable of surviving in the presence of the saline environment that can prevail in both sea water and reservoir connate water. This observation prompted further investigation into the applicability of the bacteria in microbial enhanced oil recovery. In the United Arab Emirates, the reservoirs are typically at a temperature of around 85 C. Finally, the performance of the bacteria is tested in a newly developed bioreac tor that uses continuous aeration through a transverse slotted pipe. This reactor also uses mixing without damaging the filamentous bacteria. In this process, the mecha nisms of bioremediation are identified.

Soil dynamics in an age sequence of Prosopis juliflora planted for sodic soil restoration in India

A field study was conducted to study long-term soil dynamics in Prosopis juliflora stands planted to rehabilitate degraded sodic soils in Haryana, India. Soil samples were collected from an age sequence of 0-, 5-, 7-, and, 30-yr-old plantations to assess the effects of the trees on the physical, chemical and biological properties of soil. Tree growth altered microclimate, improved soil moisture status, organic C, total N, extractable P, exchangeable Ca, Mg, and K and decreased pH, electrical conductivity and exchangeable Na levels that contributed to the reclamation of sodic sites. The dynamics reflected a three phase restoration sequence, characterized by nominal soil changes during tree establishment (0–5 yr), marked and rapid changes associated with canopy closure (5–7 yr), and gradual stabilization of soil properties in the fallow enrichment phase (7–30 yr). The ameliorative mechanisms operating in the chronosequence were categorized into two parallel sets of major processes namely: sodicity alleviation that dominated in transitional phase, and fertility restoration that characterized the fallow enrichment phase. The bioremediation mechanisms driving the reclamation processes in the reforestation of degraded sites were examined in relation to hypotheses accounting for these changes.

Mechanisms of intrinsic bioremediation of gas condensate hydrocarbons in saturated soil

Mechanisms of intrinsic bioremediation of gas condensate hydrocarbons in saturated soil