L7 - Phytoremediaton of organics

Question 1

What is inorganic arsenic classified as?

Answer 1

Group A human carcinogen

Question 2

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

Answer 2

400m

Drinking water

Question 3

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

Answer 3

• 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

Question 4

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

Answer 4

ArsC - E coli

Acr2 - Yeast

Question 5

What does ArsC expression confer?

Answer 5

Arsenate sensitivity due to toxicity of arsenite

Question 6

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

Answer 6

y-glutamycysteine synthetase

expressed it with ArsC, - increase arsenate resistance

Question 7

What did ArsC9+ECS double transformants do?

Answer 7

Accumulate 3x more arsenic

Question 8

Where is mercury a common pollutant?

Answer 8

Coolants in reactors
Ballast in submarines
Bleaching (paper)
Pesticides
Mining

Question 9

How is mercury toxic?

Answer 9

Neurotoxic and damages central nervous system

Question 10

Where has there been a mercury disaster?

Answer 10

Minamata bay in Japan

Question 11

What enzymes do bacteria use to detoxify methylmercury?

Answer 11

MerB and MerA

Question 12

What do MerB and MerA turn methylmercury into?

Answer 12

MerB to ionic mercury then MerA to metallic mercury

BOTH NOT BIOMAGNIFIED

Question 13

What did coexpression of MerA and MerB do?

Answer 13

Highest levels of methylmercury resistance

Question 14

What are the features of cottonwood trees?

Answer 14

Fast growing
deep rooted
grows best in flood plain

Question 15

What did transgenic cottonwood for MerA do?

Answer 15

Resisted high levels of ionic mercury

Question 16

What is trichloroethylene (TCE)

Answer 16

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

Question 17

What enzyme catalyses TCE metabolism?

Answer 17

Cytochrome P450 2E1 (CYP2E1)

Question 18

What plant did they transgene for metabolism of TCE?

Answer 18

Poplar

Question 19

What did the CYP2E1 transgenic poplar do?

Answer 19

Remove more TCE from air at a faster rate

Question 20

What are the features of explosives?

Answer 20

Recalcitrant

Toxic

Question 21

What are the facts of explosive pollution?

Answer 21

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

Question 22

What are the features of Massachusetts military reservation?

Answer 22

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

Question 23

Features of TNT and RDX pollution

Answer 23

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

Question 24

What were candidates for enzymatic breakdown of TNT

Answer 24

Oxyphytodienoate reductases (OPRs)

Question 25

What are the features of OPRs?

Answer 25

High sequence homology to a known microbial TNT nitroreductase

Question 26

What did knockdown of OPR 1 and 2 result in?

Answer 26

Increased sensitivity to TNT toxicity

Question 27

What did overexpression of OPR 1 result in?

Answer 27

Inreases resistance to TNT toxicity

Question 28

What are the 3 phases of detoxicifation?

Answer 28

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

Question 29

What are required for phase 2?

Answer 29

Glycosyltransferases

Question 30

How did they try to find the glycotransferases involved?

Answer 30

Microarray analysis of TNT treated Arabidopsis to see which are upregulated

Question 31

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

Answer 31

onr - pentaerythritol tetranitrate(PETN) | nfsI - classical type 1 nitroreductase

Question 32

Why are soil studies important when dealing with toxic substances?

Answer 32

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

Question 33

What did the soil studies of TNT plants show>

Answer 33

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

Question 34

What plant was chosen to break down RDX?

Answer 34

R .rhodochrous

Question 35

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

Answer 35

XplA, XplB | TNT is a potent inhibitor XplA

Question 36

What did transgenic plants for increased XplA show?

Answer 36

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

Question 37

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

Answer 37

Population capable of removing TNT and RDX from media

Question 38

Why are perennial grass species good for phytoremediation?

Answer 38

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

Question 39

How are scientists trying to biodegrade methane?

Answer 39

Bacterial methan monooxygenase into the leaves of plants