Pesticide Exposure Flashcards
Pesticides as xenobiotics(Foreign) steps.
- Synthesis and release of new chemicals and pesticides into environment
- Affects microbial communities
- Natural biochemical processes
- Alterations in natural balance
Microbes specialized features
- Highly diverse
- Under selective pressure
- Highly mutable genome
Excellent models to study fitness
- Easy to maintain and propagate in lab
* Easy to conduct molecular studies
Microbial adaptions
- The stress repair mechanisms
- Stress prevention strategies
- Escape mechanism (chemotactic movements)
Whats biotransformation?
• Chemical alteration
• Ex; conversion of 2,4-D to
2,4-DCP by Alcaligenes eutrophus
Detoxification/ bioremediation
- Conversion of toxic to non/less toxic compound
* Ex; hydrolysis of diazinon, parathion and chlorpyrifos by Flavobacterium sp.
Assimilation/ mineralization
- Conversion from organic to inorganic
* Ex; MCPA (2-methyl-4-chlorophenoxyacetic acid) mineralization by Pseudomonas sp.
Effects of pesticides on soil microbial diversity.
- Toxicity, concentration and persistence
- Adsorption, solubility, transport and degradation
- Soil properties and bioavailability ex; sandy loamy, clay
- Presence of organic matter and vegetation
Effects of pesticides on beneficial soil processes.
• Nitrogen fixation
-N2 —–> NH3
-DDT, pentachlorophenol, 2,4-D, 2,4,5-T
-Herbicides inhibited nod-expression by 32– 90% by disrupting plant– Rhizobium signaling
• Nitrification, denitrification, ammonification, and sulfur oxidation
- Impact enzymatic reactions in soil
-Mancozeb, prosulfuron, chlorothalonil, metal Dithiocarbamates
-Nitrification was inhibited by the pesticides
What happens when E.coli is exposed to sub lethal levels of 2,40- dichlorophenoxyacetic acid? How does E. coli respond?
- Toxic responses, cytotoxicity and gentoxicity
- oxidative stress
- changes to surface ultrastructure
- changes to surface elasticity and adhesion
- changes to metabolic pathways
- producing a filamentous phenotype and reactive oxygen species
Why is E. coli good at studying xenobiotics?
Its genomes, proteomes and metabolomes are well defined
How was the filamentous phenotype in E. coli from 2, 4-D reversed?
- supplementing with polyamines
- exposure to 15 mM spermidine and putrescine - polyamines protect cells from DNA damage due to oxidative stress
Oxidative stress in E.coli
-Genotoxic agents cause damage repair and blocks cell division
Whats the hypotheses in E. coli and 2,4-D?
2,4-D causes ROS production, leads to DNA damage and the SOS response - 2,4-D disrupts the cell division machinery in E. coli
Whats the goals in E. coli and 2,4-D?
- Develop a live imaging technique of E. coli by integrating AFM- confocal
- Use the technique to understand 2,4-D induced stress response mechanisms in E. coli
Advantages of AFM-LSCM?
-Live AFM • Tracking cell growth and division in live cells • Exceptional resolution • Changes to surface can be tracked in real time at nanoscale
-Live confocal
Tracking cell growth and division in live cells
Changes within the cell can be tracked in real time
Imaging is relatively fast
-Live integrated AFM-LCSM
• Probing different aspects of cell response mechanisms
• Confocal provides speed and AFM provides high resolution
What does 2,4-D impact?
- The lipophilic nature of 2,4-D and the associated oxidative stress produces a series of primary stress responses involving the alteration of surface ultrastructure, compliance and possibly DNA damage.
- Such changes lead to a series of secondary stress adaptations with reduced cell division as a main survival mechanism.
- There were changes to vital cellular pathways at sub-lethal concentrations
- Ultrastructural and morphological changes in responses were detectable at levels close to 1000 fold less than that used for field application.
What are the steps of a DNA damage assay?
- Grow E. coli
- Expose E. coli to 2,4-D
- Trap E. coli in agarose gel
- Lysis buffer- SDS Dithiothreitol
- Dry and Stain with SYBR gold
