Bioavailability of Cd, Zn and Hg in Soil to Nine Recombinant Luminescent Metal Sensor Bacteria

Sensors (Impact Factor: 2.05). 11/2008; 8(8):6899-6923. DOI: 10.3390/s8116899
Source: DOAJ

ABSTRACT A set of nine recombinant heavy metal-specific luminescent bacterial sensors belonging to Gram-negative (Escherichia and Pseudomonas) and Gram-positive (Staphylococcus and Bacillus) genera and containing various types of recombinant metal-response genetic elements was characterized for heavy metal bioavailability studies. All nine strains were induced by Hg and Cd and five strains also by Zn. As a lowest limit, the sensors were detecting 0.03 g·L -1 of Hg, 2 g·L -1 of Cd and 400 g·L -1 of Zn. Limit of determination of the sensors depended mostly on metal-response element, whereas the toxicity of those metals towards the sensor bacteria was mostly dependent on the type of the host bacterium, with Gram-positive strains being more sensitive than Gram-negative ones. The set of sensors was used to evaluate bioavailability of Hg, Cd and Zn in spiked soils. The bioavailable fraction of Cd and Zn in soil suspension assay (2.6 – 5.1% and 0.32 – 0.61%, of the total Cd and Zn, respectively) was almost comparable for all the sensors, whereas the bioavailability of Hg was about 10-fold higher for Gram-negative sensor cells (30.5% of total Hg), compared to Gram-positive ones (3.2% of the total Hg). For Zn, the bioavailable fraction in soil-water suspensions and respective extracts was comparable (0.37 versus 0.33% of the total Zn). However, in the case of Cd, for all the sensors used and for Hg concerning only Gram-negative sensor strains, the bioavailable fraction in soil-water suspensions exceeded the water-extracted fraction about 14-fold, indicating that upon direct contact, an additional fraction of Cd and Hg was mobilized by those sensor bacteria. Thus, for robust bioavailability studies of heavy metals in soils any type of genetic metal-response elements could be used for the construction of the sensor strains. OPEN ACCESS Sensors 2008, 8 6900 However, Gram-positive and Gram-negative senor strains should be used in parallel as the bioavailability of heavy metals to those bacterial groups may be different.

  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: 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.
    Critical Reviews in Environmental Science and Technology 02/2014; 44(5). · 3.24 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: This minireview explores the environmental bioremediation mediated by genetically engineered (GE) bacteria and it also highlights the limitations and challenges associated with the release of engineered bacteria in field conditions. Application of GE bacteria based remediation of various heavy metal pollutants is in the forefront due to eco-friendly and lesser health hazards compared to physico-chemical based strategies, which are less eco-friendly and hazardous to human health. A combination of microbiological and ecological knowledge, biochemical mechanisms and field engineering designs would be an essential element for successful in situ bioremediation of heavy metal contaminated sites using engineered bacteria. Critical research questions pertaining to the development and implementation of GE bacteria for enhanced bioremediation have been identified and poised for possible future research. Genetic engineering of indigenous microflora, well adapted to local environmental conditions, may offer more efficient bioremediation of contaminated sites and making the bioremediation more viable and eco-friendly technology. However, many challenges are to be addressed concerning the release of genetically engineered bacteria in field conditions. There are possible risks associated with the use of GE bacteria in field condition, with particular emphasis on ways in which molecular genetics could contribute to the risk mitigation. Both environmental as well as public health concerns need to be addressed by the molecular biologists. Although bioremediation of heavy metals by using the genetically engineered bacteria has been extensively reviewed in the past also, but the bio-safety assessment and factors of genetic pollution have been never the less ignored.
    Gene 07/2011; 480:1-9. · 2.20 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Living whole-cell bioreporters serve as environmental biosentinels that survey their ecosystems for harmful pollutants and chemical toxicants, and in the process act as human and other higher animal proxies to pre-alert for unfavorable, damaging, or toxic conditions. Endowed with bioluminescent, fluorescent, or colorimetric signaling elements, bioreporters can provide a fast, easily measured link to chemical contaminant presence, bioavailability, and toxicity relative to a living system. Though well tested in the confines of the laboratory, real-world applications of bioreporters are limited. In this review, we will consider bioreporter technologies that have evolved from the laboratory towards true environmental applications, and discuss their merits as well as crucial advancements that still require adoption for more widespread utilization. Although the vast majority of environmental monitoring strategies rely upon bioreporters constructed from bacteria, we will also examine environmental biosensing through the use of less conventional eukaryotic-based bioreporters, whose chemical signaling capacity facilitates a more human-relevant link to toxicity and health-related consequences.
    Ecological Indicators 05/2013; 28:125–141. · 3.23 Impact Factor

Full-text (3 Sources)

Available from
Jun 6, 2014