L17W10_MIC105_Xenobiotcs

L17W10_MIC105_Xenobiotcs - Biodegradation of pollutants and...

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2/17/10 1 Biodegradation of pollutants and man-made chemicals
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2/17/10 2 (Polymer of aromatic compounds)
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2/17/10 3 How are toxic and man-made (xenobiotic) chemicals degraded? - 23 million chemicals listed in Chemical Abstracts - 100,000 commercially available chemicals - new chemicals synthesized every day Biodegradation of pollutants and man-made chemicals
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2/17/10 4 Bacterial degradation of pollutants and man-made compounds Oil Agriculture Explosives UCD CH 3 OCH 2 COOH Cl Cl Cl CH 3 NO 2 NO 2 CH 3 NO 2 NO 2 CH 2 CH 3 CH 3 CH 3 BTEX CH 3 NO 2 NO 2 O 2 N PAHs TNT OCH 2 COOH Cl Cl Pesticides & herbicides Cl N N H N N N H PCBs
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2/17/10 5 Crude oil Formed from fossilized remains of plants that lived hundreds of millions of years ago. Organic carbon deposited in sediments ‘escaped’ the carbon cycle, was compacted under many layers and subjected to high temperatures and pressures. This mixture of organic compounds in sedimentary rock is called keragen , and under the right conditions is converted to fossil fuels in the form of crude oil or natural gas (hydrocarbons C,H). *
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2/17/10 6 Some hydrocarbons found in crude oil
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2/17/10 7 Polynuclear aromatic hydrocarbons (PAHs) found in creosote* *Wood preservative used to treat railroad ties, telephone poles, etc.
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2/17/10 8 Toluene CH 3 CH 2 CH 3 Benzene Ethylbenzene CH 3 CH 3 Xylenes BTEX = most soluble aromatic hydrocarbons in gasoline *
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2/17/10 9 One of the most frequently encountered sources for BTEX contamination of soil or groundwater is leaking underground gasoline or oil tanks.
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2/17/10 10 Hydrocarbon toxicity Extremely hydrophobic Can dissolve in microbial membranes Dissipate PMF (loss of energy, ability to transport nutrients, make ATP, use ±agella, etc.) Cause loss of cellular integrity: permeablize cells *
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2/17/10 11 Mechanisms used by microbes to reduce hydrocarbon toxicity Membrane modifcations to increase rigidity - cis->trans isomerization - Fewer double bonds - PL headgroup changes Solvent eF±ux pumps Release vesicles containing solvent? Metabolism *
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2/17/10 12 Hydrocarbons are very hydrophobic, poorly soluble in aqueous solution. Some bacteria produce surfactants to help solublize hydrophobic substrates *
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2/17/10 13 Pseudomonas putida F1 Obtained from contaminated creek in Urbana, IL Isolated for growth on ethylbenzene Also grows on benzene and toluene CH 2 CH 3 CH 3
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2/17/10 14 CH 3 Toluene CH 3 OH OH 3-Methylcatechol OH C O COO - CH 3 TCA Cycle O 2 O 2 Toluene degradation in Pseudomonas putida F1 Toluene dioxygenase
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15 CH 3 Toluene CH 3 OH OH 3-Methylcatechol OH C O COO - CH 3 TCA Cycle O 2 O 2 Common theme in aerobic hydrocarbon degradation: use oxygen as a substrate
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This note was uploaded on 02/16/2011 for the course MIC 105 taught by Professor Wheelis during the Spring '08 term at UC Davis.

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L17W10_MIC105_Xenobiotcs - Biodegradation of pollutants and...

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