L7 - Phytoremediaton of organics Flashcards
What is inorganic arsenic classified as?
Group A human carcinogen
How many people in India and Bangladesh are exposed to arsenic poisoning and how?
400m
Drinking water
What is the strategy for How can you optimise the candidate plant for phytoremediation of arsenic?
- Enhance uptake (AtPTs)
- Block endogenous arsenate reduction in roots ( AtACR2)
- Reduction to arsenite in leaves (ArsC)
- Detoxify and trap arsenite in thiol
- Pump thiol complexes into vacuoles
What reductases convert arsenate to arsenite and what organisms are they from?
ArsC - E coli
Acr2 - Yeast
What does ArsC expression confer?
Arsenate sensitivity due to toxicity of arsenite
What is ECS and what was done with it, and what was the result?
y-glutamycysteine synthetase
expressed it with ArsC, - increase arsenate resistance
What did ArsC9+ECS double transformants do?
Accumulate 3x more arsenic
Where is mercury a common pollutant?
Coolants in reactors Ballast in submarines Bleaching (paper) Pesticides Mining
How is mercury toxic?
Neurotoxic and damages central nervous system
Where has there been a mercury disaster?
Minamata bay in Japan
What enzymes do bacteria use to detoxify methylmercury?
MerB and MerA
What do MerB and MerA turn methylmercury into?
MerB to ionic mercury then MerA to metallic mercury
BOTH NOT BIOMAGNIFIED
What did coexpression of MerA and MerB do?
Highest levels of methylmercury resistance
What are the features of cottonwood trees?
Fast growing
deep rooted
grows best in flood plain
What did transgenic cottonwood for MerA do?
Resisted high levels of ionic mercury
What is trichloroethylene (TCE)
Solvent used for decades as metal degreaser, dry cleaning agent, solvent and anesthetic
Dumped outside after
Toxic to liver, kindey, CNS and carcinogenic
What enzyme catalyses TCE metabolism?
Cytochrome P450 2E1 (CYP2E1)
What plant did they transgene for metabolism of TCE?
Poplar
What did the CYP2E1 transgenic poplar do?
Remove more TCE from air at a faster rate
What are the features of explosives?
Recalcitrant
Toxic
What are the facts of explosive pollution?
10m he contaminated by munition
10b gallons groundwater
Treatment $16-165 bill
TNT most common
What are the features of Massachusetts military reservation?
19 plumes detected
High levels of RDX in groundwater as high as 370 ppb
EPA’s lifetime health advisory for RDX is 2 ppb
Features of TNT and RDX pollution
TNT Potent mutagen From manufacture, use and storage of munitions TNT Hydrophobic so binds soil and clay RDX hydrophilic and highly mobile Plants unable to breakdown either
What were candidates for enzymatic breakdown of TNT
Oxyphytodienoate reductases (OPRs)
What are the features of OPRs?
High sequence homology to a known microbial TNT nitroreductase
What did knockdown of OPR 1 and 2 result in?
Increased sensitivity to TNT toxicity
What did overexpression of OPR 1 result in?
Inreases resistance to TNT toxicity
What are the 3 phases of detoxicifation?
1 - reduction
2 - conjugation with sugars
3 - compartmentalisation into vacuole or well wall
What are required for phase 2?
Glycosyltransferases
How did they try to find the glycotransferases involved?
Microarray analysis of TNT treated Arabidopsis to see which are upregulated
What two enzymes did they express in tobacco to increase tolerance to TNT?
onr - pentaerythritol tetranitrate(PETN)
nfsI - classical type 1 nitroreductase
Why are soil studies important when dealing with toxic substances?
Soil bacteria play essential role in nutrient cycling and decomposition
Plant provide primary energy source to soil microorganisms so must be investigated
What did the soil studies of TNT plants show>
No significant effect on microbial community when no TNT present
Big increase when TNT present
What plant was chosen to break down RDX?
R .rhodochrous
What enzymes are used to break down RDX and what is the problem with this?
XplA, XplB
TNT is a potent inhibitor XplA
What did transgenic plants for increased XplA show?
Less accumulation of RDX so less will be returned when plant dies than wild type
What did crossing NR with RDX-degrading lines lead to?
Population capable of removing TNT and RDX from media
Why are perennial grass species good for phytoremediation?
Ability to grow and cover ground year round and wide geographic distribution
How are scientists trying to biodegrade methane?
Bacterial methan monooxygenase into the leaves of plants
