Lecture 9 Whyte Flashcards
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
T
Cl-C bonds are relatively very strong and very _________ to break
difficult
What determines the biodegradability of halogenated phenolic compounds?
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)
What are the major steps in the biodegradation of halogenated organic compounds?
- debranching ring breakage
- dehalogenation/hydroxylation
- ring cleavage/ oxidation & reduction
The degradation of agent orange (2,4,5,-T) gives:
succinate + acetate that go directly to the citric acid cycle
Dehalogenation is the ____ step
key
Often but not always the first step in biodegradation of simple haloaromatic compounds can occur anaerobiclly or aerobically:
dehalogenation
Aerobic dehalogenation of dichloromethane by ________________
Hyphomicrobium dehalogenase
Aerobic dehalogenation of 2-chlorobenzoate via ____________
mono-dioxygenases
PCP =
pentachlorophenol
PCP biodegradation can occur __________ or ____________
aerobically or anaerobically
Herbicide, insecticide, fungicide, algaecide, and disinfectant:
pentachlorophenol
T or F: the use of PCP has declined due to its high toxicity and slow biodegradation
T
Anaerobic biodegradation of PCP is usually done by ___________________
reductive dechlorination
DDT when loses one chloride is now _________
DDD
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 ________________________
hydrogenolytic reductive dechlorination
T or F: PCBs are highly stable at higher temperatures
T
Pentachlorobiphenyl can be dehalogenated by anaerobic bacteria such as ______________________
Dehalococcoides ethenogenes strain 195
Pathway of aerobic PCB degradation by _______________ bacteria. Results in accumulation of __________ which are difficult to biodegrade further
biphenyl-oxidizing
chlorobenzoates
T or F: TCDD are extremely toxic and highly resistant to biodegradation
T
2,4-Dichlorophenoxyacetic acid (2,4-D) is a common ______________ used to control broadleaf weeds
pesticide/herbicide
One of the most widely used herbicides worldwide:
2,4-Dichlorophenoxyacetic acid
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!
T
_______ is a pesticide famous for silent spring = kill birds no more chanting
DDT
DDT is an organochloride pesticide used extensively since the 1940s for the control of _______________ and vector-borne diseases like _________ and typhus 1
agricultural pests
malaria
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
T
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.
T
Biodegradation of nitroaromatic (explosive) compounds can be done ______________ or ______________
anaerobically
aerobically
The aerobic biodegradation of nitroaromatic compounds occur when:
nitro groups are cleaved off via monooxygenase or dioxygenase activity
The anaeerobic biodegradation of nitroaromatic compounds occur when:
nitro groups are reduced (used as terminal electron acceptors)
The reduction of trinitrotoluene (TNT) to triaminotoluene (TAT) by Clostridium or Desulfovibrio is an example of
anaerobically biodegradation of nitroaromatic compounds
The reductive biodegradation of nitrobenzene by Comamonas sp. is an example of
anaerobically biodegradation of nitroaromatic compounds
____________ are where the biodegradative pathways are encoded
plasmids
C.necator strain JMS24 is used for:
biodegradation of PCBs in soils
TCE =
trichloroethylene
T or F: TCE and PCE are common industrial solvents used to clean machineries. They are toxic, carcinogenic, common ground water contaminant
T
