Pesticide Exposure

Question 1

Pesticides as xenobiotics(Foreign) steps.

Answer 1

1. Synthesis and release of new chemicals and pesticides into environment
2. Affects microbial communities
3. Natural biochemical processes
4. Alterations in natural balance

Question 2

Microbes specialized features

Answer 2

• Highly diverse
• Under selective pressure
• Highly mutable genome

Question 3

Excellent models to study fitness

Answer 3

• Easy to maintain and propagate in lab

* Easy to conduct molecular studies

Question 4

Microbial adaptions

Answer 4

• The stress repair mechanisms
• Stress prevention strategies
• Escape mechanism (chemotactic movements)

Question 5

Whats biotransformation?

Answer 5

• Chemical alteration
• Ex; conversion of 2,4-D to
2,4-DCP by Alcaligenes eutrophus

Question 6

Detoxification/ bioremediation

Answer 6

• Conversion of toxic to non/less toxic compound

* Ex; hydrolysis of diazinon, parathion and chlorpyrifos by Flavobacterium sp.

Question 7

Assimilation/ mineralization

Answer 7

• Conversion from organic to inorganic

* Ex; MCPA (2-methyl-4-chlorophenoxyacetic acid) mineralization by Pseudomonas sp.

Question 8

Effects of pesticides on soil microbial diversity.

Answer 8

1. Toxicity, concentration and persistence
2. Adsorption, solubility, transport and degradation
3. Soil properties and bioavailability ex; sandy loamy, clay
4. Presence of organic matter and vegetation

Question 9

Effects of pesticides on beneficial soil processes.

Answer 9

• 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

Question 10

What happens when E.coli is exposed to sub lethal levels of 2,40- dichlorophenoxyacetic acid? How does E. coli respond?

Answer 10

• 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

Question 11

Why is E. coli good at studying xenobiotics?

Answer 11

Its genomes, proteomes and metabolomes are well defined

Question 12

How was the filamentous phenotype in E. coli from 2, 4-D reversed?

Answer 12

• supplementing with polyamines

- exposure to 15 mM spermidine and putrescine - polyamines protect cells from DNA damage due to oxidative stress

Question 13

Oxidative stress in E.coli

Answer 13

-Genotoxic agents cause damage repair and blocks cell division

Question 14

Whats the hypotheses in E. coli and 2,4-D?

Answer 14

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

Question 15

Whats the goals in E. coli and 2,4-D?

Answer 15

• 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

Question 16

Advantages of AFM-LSCM?

Answer 16

-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

Question 17

What does 2,4-D impact?

Answer 17

• 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.

Question 18

What are the steps of a DNA damage assay?

Answer 18

1. Grow E. coli
2. Expose E. coli to 2,4-D
3. Trap E. coli in agarose gel
4. Lysis buffer- SDS Dithiothreitol
5. Dry and Stain with SYBR gold