I am working on bio-remediation (hyper accumulators+bacteria) of heavy metals and want to test bacterial strains that are only metal specific. i.e. one strain for each metal..
It has been suggested that metal specific bacteria can be recognized based on the combination of traditional ecotoxicology methods and metal-specific recombinant biosensors allowed to clearly differentiate the toxic effects of metal oxides per se and solubilized metal ions. I guess that a single bacterial species may have many receptors for a specific metal. More expert opinion can be requested to microbiologists.
I know a PhD from my University who works with certain bacteria species and these bacteria are being used for the bioremediation of chromium. When I saw the results, the tests indicated these bacteria tend to accumulate only chromium. It was either III or VI oxidation state.
The rhizosphere microbial populations are known to affect heavy metal mobility and availability to the plant through the release of chelating agents, acidification, phosphate solubilization and redox changes, and therefore, have potential to enhance phytoremediation processes.
The chelating agent like Ethylenediaminetetraacetate (EDTA), which successfully utilized to enhance phytoextraction of lead and other metals from contaminated soils. Phytochelators in making the heavy metals, bio-available to the plant and their symbionts in enhancing the uptake of bio-available heavy metals.
The use of rhizosphere bacteria in combination with plants is expected to provide high efficiency for metal uptake from the soil. Rhizosphere microorganisms, which are closely associated with roots, have been termed plant growth promoting rhizobacteria. Research has also shown that many rhizobacteria are tolerant to heavy metals and play important roles in the mobilization or immobilization of heavy metals. In one of the study it is reported that the addition of Sphingomonas macrogoltabidus, Microbacterium arabinogalactanolyticum and Microbacterium liquefaciens to the plant Alyssum murale grown in serpentine soil significantly increased the plant uptake of Ni.
Among soil microorganisms, mycorrhizal fungi are the only ones providing a direct link between soil and roots, and can therefore be of great importance in heavy metal availability to hyperaccumulators plants.
Some references about rhizosphere soil microorganisms that enhance metal uptake in hyperaccumulators are as follows:
1. Chaudhry TM and AG Khan (1998). Role of symbiotic micro-organisms in sustainable plant growth on heavy metal contaminated industrial sites. In: Microbial Technology for Sustainable Development and Productivity (Ed. Rajak, RC) Scientific Publishers, Jabalpur, 270-279.
2. Khan AG, C Kuek, TM Chaudhry, CS Khoo, WJ Hayes (2000). Role of plants, mycorrhizae and phytochelators in heavy metal contaminated land remediation. Chemosphere 41 (1), 197-207.
3. Li WC, ZH Ye, MH Wong (2007). Effects of bacteria on enhanced metal uptake of the Cd/Zn-hyperaccumulating plant, Sedum alfredii. Journal of Experimental Botany 58 (15/16), 4173–4182.
4. Kuffner M, M Puschenreiter, G Wieshammer, M Gorfer, A Sessits (2008). Rhizosphere bacteria affect growth and metal uptake of heavy metal accumulating willows. Plant Soil 304, 35–44.
5. Jing Yan-de, Zhen-li He, Xiao-e Yang (2007). Role of soil rhizobacteria in phytoremediation of heavy metal contaminated soils. J Zhejiang Univ Sci B. 8(3), 192–207.
6. Weissenhorn I, C. Leyval, G. Belgy, J. Berthelin (1995). Arbuscular mycorrhizal contribution to heavy metal uptake by maize (Zea mays L.) in pot culture with contaminated soil. Mycorrhiza 5 (4), 245-251.
You should isolate the bacteria from particular metal contaminated site. And then check there metal mobilization activities in lab to find out either they can mobilize the (particular) metal or not. If they can able to mobilize metal then they will help you in microbe assisted phytoremediation.
I agree with Tm Chaudhry. The rhizosphere is a unique home of most of the bacteria employed in bioaccumulation of heavy metals. Moreover, lot of thanks and good wishes to Saeed for doing works on this topic.
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