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Bioremediation > L7 - Phytoremediaton of organics > Flashcards

L7 - Phytoremediaton of organics Flashcards

1
Q

What is inorganic arsenic classified as?

A

Group A human carcinogen

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2
Q

How many people in India and Bangladesh are exposed to arsenic poisoning and how?

A

400m

Drinking water

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3
Q

What is the strategy for How can you optimise the candidate plant for phytoremediation of arsenic?

A
  • 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
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4
Q

What reductases convert arsenate to arsenite and what organisms are they from?

A

ArsC - E coli

Acr2 - Yeast

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5
Q

What does ArsC expression confer?

A

Arsenate sensitivity due to toxicity of arsenite

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6
Q

What is ECS and what was done with it, and what was the result?

A

y-glutamycysteine synthetase

expressed it with ArsC, - increase arsenate resistance

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7
Q

What did ArsC9+ECS double transformants do?

A

Accumulate 3x more arsenic

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8
Q

Where is mercury a common pollutant?

A 
Coolants in reactors
Ballast in submarines
Bleaching (paper)
Pesticides
Mining
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9
Q

How is mercury toxic?

A

Neurotoxic and damages central nervous system

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10
Q

Where has there been a mercury disaster?

A

Minamata bay in Japan

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11
Q

What enzymes do bacteria use to detoxify methylmercury?

A

MerB and MerA

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12
Q

What do MerB and MerA turn methylmercury into?

A

MerB to ionic mercury then MerA to metallic mercury

BOTH NOT BIOMAGNIFIED

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13
Q

What did coexpression of MerA and MerB do?

A

Highest levels of methylmercury resistance

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14
Q

What are the features of cottonwood trees?

A

Fast growing
deep rooted
grows best in flood plain

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15
Q

What did transgenic cottonwood for MerA do?

A

Resisted high levels of ionic mercury

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16
Q

What is trichloroethylene (TCE)

A

Solvent used for decades as metal degreaser, dry cleaning agent, solvent and anesthetic
Dumped outside after
Toxic to liver, kindey, CNS and carcinogenic

17
Q

What enzyme catalyses TCE metabolism?

A

Cytochrome P450 2E1 (CYP2E1)

18
Q

What plant did they transgene for metabolism of TCE?

A

Poplar

19
Q

What did the CYP2E1 transgenic poplar do?

A

Remove more TCE from air at a faster rate

20
Q

What are the features of explosives?

A

Recalcitrant

Toxic

21
Q

What are the facts of explosive pollution?

A

10m he contaminated by munition
10b gallons groundwater
Treatment $16-165 bill
TNT most common

22
Q

What are the features of Massachusetts military reservation?

A

19 plumes detected
High levels of RDX in groundwater as high as 370 ppb
EPA’s lifetime health advisory for RDX is 2 ppb

23
Q

Features of TNT and RDX pollution

A 
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
24
Q

What were candidates for enzymatic breakdown of TNT

A

Oxyphytodienoate reductases (OPRs)

25
Q

What are the features of OPRs?

A

High sequence homology to a known microbial TNT nitroreductase

26
Q

What did knockdown of OPR 1 and 2 result in?

A

Increased sensitivity to TNT toxicity

27
Q

What did overexpression of OPR 1 result in?

A

Inreases resistance to TNT toxicity

28
Q

What are the 3 phases of detoxicifation?

A

1 - reduction
2 - conjugation with sugars
3 - compartmentalisation into vacuole or well wall

29
Q

What are required for phase 2?

A

Glycosyltransferases

30
Q

How did they try to find the glycotransferases involved?

A

Microarray analysis of TNT treated Arabidopsis to see which are upregulated

31
Q

What two enzymes did they express in tobacco to increase tolerance to TNT?

A

onr - pentaerythritol tetranitrate(PETN)

nfsI - classical type 1 nitroreductase

32
Q

Why are soil studies important when dealing with toxic substances?

A

Soil bacteria play essential role in nutrient cycling and decomposition
Plant provide primary energy source to soil microorganisms so must be investigated

33
Q

What did the soil studies of TNT plants show>

A

No significant effect on microbial community when no TNT present
Big increase when TNT present

34
Q

What plant was chosen to break down RDX?

A

R .rhodochrous

35
Q

What enzymes are used to break down RDX and what is the problem with this?

A

XplA, XplB

TNT is a potent inhibitor XplA

36
Q

What did transgenic plants for increased XplA show?

A

Less accumulation of RDX so less will be returned when plant dies than wild type

37
Q

What did crossing NR with RDX-degrading lines lead to?

A

Population capable of removing TNT and RDX from media

38
Q

Why are perennial grass species good for phytoremediation?

A

Ability to grow and cover ground year round and wide geographic distribution

39
Q

How are scientists trying to biodegrade methane?

A

Bacterial methan monooxygenase into the leaves of plants

Bioremediation (9 decks)

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