The role of cell characteristic on sunlight-mediated photochemical disinfection in agricultural...
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The role of cell characteristic on sunlight-mediated photochemical disinfection in agricultural run-off waters James Gutierrez- BRITE Student Amy Gong-BRITE Mentor Dr. Sharon Walker- BRITE Faculty Advisor UCR Bacterial Adhesion Research Laboratory
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Transcript of The role of cell characteristic on sunlight-mediated photochemical disinfection in agricultural...
The role of cell characteristic on sunlight-mediated
photochemical disinfection in agricultural run-off waters
James Gutierrez- BRITE StudentAmy Gong-BRITE Mentor
Dr. Sharon Walker- BRITE Faculty Advisor
UCR Bacterial Adhesion Research Laboratory
Relevance
http://www.pcee.org/Images/Images_Questions/06_12_11_point_non_point.gif
Cellular Characteristic
Zeta Potential
Hydrophobicity
Cell Lysis test
EPS analysis
Size
Viability
Surface charge
What are Extracellular Polymeric Substances?
Copyright © 2008 American Chemical Society
•Amount and composition vary due to physiology, growth phase, pH, temperature and other environmental factors
•Made up (usually) primarily of polysaccharides (sugars) and proteins with traces amounts of nucleic acids
EPS extraction methods
• Azeredo and Lazarova• Cold ethanol• Sonication
+
•Simplified systemNo addition “quenchers” are neededNo catalyst needed
•Common pollutant from agricultural run off
Photo-chemical Transformation
NO3-
.NO3- + NO3
- NO2- + O(3P)
NO2- + .O-
Followed by
.O- + H2O .OH + OH-
light
Why Nitrate?
Halmann, M. M. (1996). Photodegradation of water pollutants. Boca Raton: CRC Press.
How Hydroxyl Radical kills
• Disrupts the cell membrane
D21G Photolysis
Viability change over time
0.01
0.10
1.00
10.00
100.00
0 100 200 300 400 500
sunlight exposure (min)
Via
bili
ty (
%)
0 mM KNO3, no light
0 mM KNO3, sunlight
10 mM KNO3, no light
10 mM KNO3, sunlight
100 mM KNO3, no light
100 mM KNO3, sunlight
Population change over time
1.000E+05
1.000E+06
1.000E+07
1.000E+08
0 100 200 300 400 500
sunlight exposure (min)
Ba
cte
ria
l po
pu
lati
on
0 mM KNO3, no light
0 mM KNO3, sunlight
10 mM KNO3, no light
10 mM KNO3, sunlight
100 mM KNO3, no light
100 mM KNO3, sunlight
Ln Bacteria Concetration change over time
14.500
15.000
15.500
16.000
16.500
17.000
17.500
18.000
18.500
0 100 200 300 400 500
sunlight exposure (min)
Ln
co
nc
etr
ati
on
0 mM KNO3, no light
0 mM KNO3, sunlight
10 mM KNO3, no light
10 mM KNO3, sunlight
100 mM KNO3, no light
100 mM KNO3, sunlight
Linear (0 mM KNO3,sunlight)Linear (10 mM KNO3,sunlight)Linear (100 mM KNO3,sunlight)
Population change over time
1.E+04
1.E+05
1.E+06
1.E+07
1.E+08
1.E+09
0 100 200 300 400 500
sunlight exposure (min)
Ba
cte
ria
l po
pu
lati
on
0 mM KNO3, no light
0 mM KNO3, sunlight
10 mM KNO3, no light
10 mM KNO3, sunlight
100 mM KNO3, no light
100 mM KNO3, sunlight
HU1 Photolysis
Viability change over time
0.01
0.10
1.00
10.00
100.00
0 50 100 150 200 250 300 350 400
sunlight exposure (min)
Via
bili
ty (
%)
0 mM KNO3, no light
0 mM KNO3, sunlight
10 mM KNO3, no light
10 mM KNO3, sunlight
100 mM KNO3, no light
100 mM KNO3, sunlight
Ln Bacteria Concentration change over time
14.000
14.500
15.000
15.500
16.000
16.500
17.000
17.500
18.000
18.500
19.000
0 50 100 150 200 250 300 350 400
sunlight exposure (min)
Ln
co
nc
etr
ati
on
0 mM KNO3, no light
0 mM KNO3, sunlight
10 mM KNO3, no light
10 mM KNO3, sunlight
100 mM KNO3, no light
100 mM KNO3, sunlight
Linear (10 mM KNO3,sunlight)
Linear (100 mM KNO3,sunlight)
Population change over time
1.0E+04
1.0E+05
1.0E+06
1.0E+07
1.0E+08
1.0E+09
0 100 200 300 400 500
sunlight exposure (min)
Ba
cte
ria
l po
pu
lati
on
0 mM KNO3, no light
0 mM KNO3, sunlight
10 mM KNO3, no light
10 mM KNO3, sunlight
100 mM KNO3, no light
100 mM KNO3, sunlight
DC1 Photolysis
Viability change over time
0.01
0.10
1.00
10.00
100.00
0 100 200 300 400 500
sunlight exposure (min)
Via
bili
ty (
%)
0 mM KNO3, no light
0 mM KNO3, sunlight
10 mM KNO3, no light
10 mM KNO3, sunlight
100 mM KNO3, no light
100 mM KNO3, sunlight
Ln Bacteria Concetration over time
13.000
14.000
15.000
16.000
17.000
18.000
19.000
0 100 200 300 400 500
sunlight exposure (min)
Ln
Co
nc
etr
ati
on
0 mM KNO3, no light
0 mM KNO3, sunlight
10 mM KNO3, no light
10 mM KNO3, sunlight
100 mM KNO3, no light
100 mM KNO3, sunlight
Linear (10 mM KNO3,sunlight)
Linear (100 mM KNO3,sunlight)
Hydrophobicity
0%
20%
40%
60%
80%
100%
D21G HU1 DC1
Microbial Adhesion to Hydrocarbon (MATH) test
Zeta Potential
-70
-60
-50
-40
-30
-20
-10
0
D21G HU1 DC1
mV
EPS
Cell Type Mean Sugara
Content(mg/cell x 1011)
Mean Proteinb Content
(mg/cell x 1011)
Average Sugar to
Protein Ratio
Average Cell Concentration(1011 bac/mL)
D21g 2.62 58.78 0.05 0.30
HU1 2.08 76.16 0.04 0.42
DC1 1.41 61.21 0.04 0.61
a Based on Xanthan gum as the standard. b Based on Bovine Serum Albumin (BSA) as the standard.
Discussion
• Increased concentration of nitrate increases bacterial kill rates. Further work will include Dissolved Organic Matter.
• Yet to identify the role of EPS. We suspect that EPS is assisting the bactericidal effect.
Future work
• Finish tests in triplicate• Begin testing in Sun simulator with low, medium
and high EPS E. coli strains• Quantify the reaction rate and rate constants for
bactericide• Identify solution chemistry effect of the
photochemical disinfection• Optimized condition for the reaction to take
place
Acknowledgments
• The BRITE program and BRITE participants.
• UCR Bacterial Adhesion Research Lab members
• Dr. Sharon Walker
• Amy Gong
