Lecture 9 Whyte

Question 1

T or F: Organic molecules which are halogenated (containing Cl, Fl, Br molecules attached to the organic compound) are almost always more difficult to degrade than it’s non-halogenated counterpart

Answer 1

T

Question 2

Cl-C bonds are relatively very strong and very _________ to break

Answer 2

difficult

Question 3

What determines the biodegradability of halogenated phenolic compounds?

Answer 3

Molecules with a greater degree of halogenation are usually more recalcitrant, but the general complexity of the molecule may also be important (more complex = more recalcitrant to biodegradation)

Question 4

What are the major steps in the biodegradation of halogenated organic compounds?

Answer 4

• debranching ring breakage
• dehalogenation/hydroxylation
• ring cleavage/ oxidation & reduction

Question 5

The degradation of agent orange (2,4,5,-T) gives:

Answer 5

succinate + acetate that go directly to the citric acid cycle

Question 6

Dehalogenation is the ____ step

Answer 6

key

Question 7

Often but not always the first step in biodegradation of simple haloaromatic compounds can occur anaerobiclly or aerobically:

Answer 7

dehalogenation

Question 8

Aerobic dehalogenation of dichloromethane by ________________

Answer 8

Hyphomicrobium dehalogenase

Question 9

Aerobic dehalogenation of 2-chlorobenzoate via ____________

Answer 9

mono-dioxygenases

Question 10

PCP =

Answer 10

pentachlorophenol

Question 11

PCP biodegradation can occur __________ or ____________

Answer 11

aerobically or anaerobically

Question 12

Herbicide, insecticide, fungicide, algaecide, and disinfectant:

Answer 12

pentachlorophenol

Question 13

T or F: the use of PCP has declined due to its high toxicity and slow biodegradation

Answer 13

T

Question 14

Anaerobic biodegradation of PCP is usually done by ___________________

Answer 14

reductive dechlorination

Question 15

DDT when loses one chloride is now _________

Answer 15

DDD

Question 16

Microorganisms at the contaminated site provide H2 as a natural byproduct of various fermentation reactions.. the dechlorinating bacteria use this H2 as their electron donor, ultimately replacing chlorine atoms in the chloroethenes with hydrogen atoms via ________________________

Answer 16

hydrogenolytic reductive dechlorination

Question 17

T or F: PCBs are highly stable at higher temperatures

Answer 17

T

Question 18

Pentachlorobiphenyl can be dehalogenated by anaerobic bacteria such as ______________________

Answer 18

Dehalococcoides ethenogenes strain 195

Question 19

Pathway of aerobic PCB degradation by _______________ bacteria. Results in accumulation of __________ which are difficult to biodegrade further

Answer 19

biphenyl-oxidizing

chlorobenzoates

Question 20

T or F: TCDD are extremely toxic and highly resistant to biodegradation

Answer 20

T

Question 21

2,4-Dichlorophenoxyacetic acid (2,4-D) is a common ______________ used to control broadleaf weeds

Answer 21

pesticide/herbicide

Question 22

One of the most widely used herbicides worldwide:

Answer 22

2,4-Dichlorophenoxyacetic acid

Question 23

T or F: 2,4-D is toxic, carcinogenic, causes neurotoxicity, liver damage, sometimes contaminated with dioxins. But it is readily biodegraded by a wide range of bacteria in soil and water, 1/2 life in soil of 2 to 16 days!

Answer 23

T

Question 24

_______ is a pesticide famous for silent spring = kill birds no more chanting

Answer 24

DDT

Question 25

DDT is an organochloride pesticide used extensively since the 1940s for the control of _______________ and vector-borne diseases like _________ and typhus 1

Answer 25

agricultural pests

malaria

Question 26

T or F: DDT is toxic and very recalcitrant to degradation with the half-life of 4-30 years. It’s major metabolites DDD and DDE are more toxic and recalcitrant than the parent compound

Answer 26

T

Question 27

T or F: As priority persistant organic pollutants (POPs) and endocrine-disrupting chemicals (EDCs), exposure to DDT can cause a wide range of acute and chronic effects including carcinogenesis, estrogenic action, and endocrine disruption, posing a serious risk to environmental and human health.

Answer 27

T

Question 28

Biodegradation of nitroaromatic (explosive) compounds can be done ______________ or ______________

Answer 28

anaerobically

aerobically

Question 29

The aerobic biodegradation of nitroaromatic compounds occur when:

Answer 29

nitro groups are cleaved off via monooxygenase or dioxygenase activity

Question 30

The anaeerobic biodegradation of nitroaromatic compounds occur when:

Answer 30

nitro groups are reduced (used as terminal electron acceptors)

Question 31

The reduction of trinitrotoluene (TNT) to triaminotoluene (TAT) by Clostridium or Desulfovibrio is an example of

Answer 31

anaerobically biodegradation of nitroaromatic compounds

Question 32

The reductive biodegradation of nitrobenzene by Comamonas sp. is an example of

Answer 32

anaerobically biodegradation of nitroaromatic compounds

Question 33

____________ are where the biodegradative pathways are encoded

Answer 33

plasmids

Question 34

C.necator strain JMS24 is used for:

Answer 34

biodegradation of PCBs in soils

Question 35

TCE =

Answer 35

trichloroethylene

Question 36

T or F: TCE and PCE are common industrial solvents used to clean machineries. They are toxic, carcinogenic, common ground water contaminant

Answer 36

T