Bioremediation of radioactive waste from the sea using Deinococcus Radiodurans Essay


Thousands of waste sites around the universe contain non-degradable radioactive stuff. A batch of danger and disbursal of cleaning up such wastes by physicochemical methods and therefore the other methods are being pursued for killing of those sites. One effectual method is to engineer radiation-resistance bugs that degrade or transform such wastes into less risky compounds. Deinococcus radiodurans, the most radiation-resistance being of all time known and endure 1,500 Kilorad/hr gamma or UV radiation and grow in radioactive environment. This characteristic is utile for redress of radioactive waste stuff by presenting the cistron from Pseudomonas putida spp. into Deinococcus radiodurans genome ( strain R1- ATCC BAA-816 ) which is responsible for debasement. This recombinant strain will degrade the harmful radioactive stuff and clean up the sea environment by change overing into less harmful compounds.

Introduction and Background:

Nuclear arm production in earlier 5 decennaries has generated most of the wastes which was straight discharged into the H2O and now are polluting 1000s of sites. In the United States, approximately one tierce of the reported waste sites are radioactive, with radiation degrees every bit high as 10 mCi/L in or shut to the contaminating beginnings ( 14 ) . These extremely toxic wastes contain inorganic and organic contaminations that include radionuclide such as 235Uranium, heavy metals such as quicksilver, and dissolvers such as methylbenzene ( 14 ) .

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There is small chance for killing of these waste sites by physicochemical method entirely because of utmost disbursal, danger and strength of labour. The clean-up cost of these waste sites by physicochemical method was estimated to be $ 90 billion 1988 and more late to be about $ 265 billion ( 15 ) . Unless new costs effectual clean up engineerings are developed, theses waste increasing will endanger to the marine life and worlds.

Numerous beings ( peculiarly Pseudomonas sp. ) have been described that have the ability to degrade, transform and detoxicate the organic and inorganic pollutants ( 16-21 ) . Most of the microorganisms are sensitive to the detrimental consequence of radiation found in the radioactive waste and are non suited for redress of radioactive waste stuff. Therefore, radiation-resistant microorganisms that can degrade radioactive waste stuff demand to be found in nature or engineered in the research lab to work out this job.

The most radiation opposition being is discovered till now is Deinococcus radiodurans ( Figure-1 ) ( 22-23 ) . It is pink is colour because of carotenoid pigment nowadays in it. It consists of 4-10 indistinguishable transcripts of a chromosome ( 2.65 Mbp ) , two megaplasmid ( 412 and 177 kbp ) and a plasmid ( 46 kbp ) ( 4-6 ) . This is a non-pathogenic, spherical shaped, Gram Positive aerophilic bacteriums bacteria that can turn continuously in the presence of I? 1,500 Kilorad/hr Gamma or UV radiation with no consequence on either its growing rate or its ability to show foreign cistrons ( 27 ) .

Figure-1 Deinococcus radiodurans ( 6 )

Deinococcus radiodurans bacteria has the capableness to turn in the radioactive environment. This belongings is really utile for bioremediation of radioactive substances by integrating cistrons from the Pseudomonas putida sp. The ability of a micro-organism to rectify the radioactive waste stuff is associated with the ability to transform these stuffs into less harmful compounds.

Toluene is non-water-soluble liquid of benzine derived function. It is an aromatic hydrocarbon and if inhaled in big sum, it causes neurological injury which may take to decease besides. When it is assorted in the H2O, it is hard to degrade methylbenzene. A Deinococcus radiodurans bacteria does non hold a cistron to degrade methylbenzene. So, when this bacteria is engineered by adding TOD cistron from E. coli sp. , it is able to degrade methylbenzene ( 1 ) .

Metallic elements like Hg, in ionic are really toxic. When Hg ( II ) is assorted with H2O it takes batch of clip to degrade of course. So, when the cistron responsible for degrading ionic Hg ( II ) that is Hg ( II ) opposition cistron ( merA ) from E. coli strain BL308 into Deinococcus radiodurans, it resist the toxic consequence of the metal and transform those metals to less toxic and less soluble chemical provinces ( 2 ) .

IR immune bacteriums Deinococcus radiodurans have high intracellular concentration of Mn/Fe ratio. When high degree of radiation exposed to the bacteria, its primary mark of biological action is on protein non on DNA. Mn ( II ) ions are distributed all over the cell but Fe is present in a part where cell division takes topographic point. Mn ( II ) ions protects protein from oxidative alterations by presenting carbonyl group into it ( 9-10 ) .

The most studied of Deinococcus sp. is D. radiodurans. Unlike other species of deinobacteria, it is most apt and comfy to familial use due to its natural transformability by both high molecular weight chromosomal DNA and plasmid DNA ( 28-29 ) . The natural ability of transmutation of this bacteria has enlightened the many different techniques for familial alternation enabling it extremely for molecular probe ( 29-31 ) .

The purpose of this undertaking is to engineer a strain of D. radiodurans that are capable of degrading radioactive waste stuff. Well known being those are capable of degrading wastes are non able to last in these sites because of their sensitiveness to the radiations. By and large, most of the beings are sensitive to the detrimental effects of ionising radiation and most of the bacteriums presently being studied are non acceptable to rectify radioactive waste. For illustration, Pseudomonas sp. is really sensitive to radiation ( more sensitive than E. coli ) and non suited to rectify radioactive waste. Therefore, radiation immune beings are needed to be found in the nature or engineered in the research lab that can rectify radioactive wastes.

Statement of Research Objectives, Methods and Significance:

The chief aims of this undertaking are:

To insulate the cistron of involvement.

To present the coveted cistron into D. radiodurans.

To analyze the look in D. radiodurans.

To optimise the media composing for better consequences.

My working hypothesis is that a Deinococcus radiodurans bacteria grows in radioactive environment. This can be used for bioremediation of radioactive substances. It would be doing possible by integrating cistrons responsible for debasement of waste stuff from Pseudomonas putida spp.

Goal 1- D. radiodurans will be grown on TYG broth medium and P. putida on Basal Salt Medium. Chromosomal DNA is isolated and plasmid DNA is isolated from P. putida ( 36 ) . Restriction digestion of plasmid DNA and Chromosomal DNA will be done to cut the specific part of DNA ( 37 ) . Electrophoresis of limitation digested DNA will be the following measure to look into their Deoxyribonucleic acid is cut at the specific site. Plasmid DNA will be extracted by utilizing electro-elution. Centrifuge the eluted Deoxyribonucleic acid with dialysis buffer which will take contaminated agarose atoms.

Goal 2- A ringer will be prepared by presenting the cistron from P. putida to D. radiodurans by transmutation. pl3 shuttle vector is used for transmutation ( 32 ) .

Figure- 2 D. radiodurans plasmid and relevant genotype ( 38 )

Horizontal cistron transportation can be done in assorted ways like transduction, bacterial junction and cistron transportation agents ( 35 ) . But transmutation is the outstanding method to reassign a cistron from one micro-organism to another micro-organism.

Figure-2 Examples of Horizontally transferred cistrons in D. radiodurans ( 34 )

Goal 3- Once the cistron is transferred to D. radiodurans from P. putida, testing will be the following measure. It will be done by two methods-Gel Shift and Colony PCR. Gel displacement ( EMSA- Electrophoretic Mobility Shift Assay ) method will find the difference between the transformed DNA and non-transformed DNA. Transformed DNA will run easy on gel because of its high molecular weight than the non-transformed DNA. By comparing with the marker DNA, it will be easy to visualise the differences. Colony PCR method determines the insert size or orientation in the vector. If the insert is present, the size of the vector will increase. This can be determined by turning each settlement in the liquid medium and plasmid so purified by rapid boiling method digestion by limitation enzymes that excise the insert, followed by separation on agarose gel cataphoresis.

Goal 4- When a cloned D. radiodurans is ready, media optimisation will be important for faster growing of the cloned transcripts. Radioactive stuff concentration will be changed from lower to higher concentration. Higher and lower glucose concentration will be changed for better consequences. Some other elements will be added if required.


6 months

Year 1


Growth of Bacteria and DNA isolation

Electrophoresis and Electroeloculation




Bioassay for screening- Gel Shift

Colony PCR


Media Optimization

Future Research Directions-

A long term end of this undertaking is to engineer the cloned copied of D. radiodurans genetically so that it will overexpress. However, to overexpress the cloned transcripts, foremost the complete cistron sequence, boosters and regulators must be identified and understood. If the consequences are non satisfactorily good, utilize different beings alternatively of P. putida. Actual field test of this being and if it is successful big scale production of this being would be the last measure.


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