Nicole Chou              May.11.2010
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Nicole Chou May.11.2010. Nicole Chou May.11.2010. Nicole Chou May.11.2010. Global Water Situation. Water Scarcity. Billion people have no access to an improved water supply and far more lack access to safe water. SODIS (Solar Water Disinfection).

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Global water situation
Global Water Situation

Water Scarcity

Billion people have no access to an improved water supply and far more lack access to safe water.


Sodis solar water disinfection
SODIS (Solar Water Disinfection)

SODIS is a low -cost simple household water treatment method .

Expose drinking water in plastic bottle to sunlight for more than 6 hours.

 Mainly use solar radiation (UVA specific)

 Synergistic effect will occur if water temperature rise above 50 oC

** A positive impact on health has been documented in several epidemiological field studies. For example, In India, where a total 40% of diarrhea diseases and 50% of severe diarrhea episodes were prevented by use of SODIS.


Purpose of this research
Purpose Of This Research

- To measure the effectiveness of SODIS

 By define the inactivation pattern of mechanisms.

To define the ability of survive and repair damage

- To confirm that temperature is not predominant factor in the elimination of bacteria.


Materials and methods
Materials and Methods

  • Enteric Bacterium

    - Gram-negative rod shape bacteria. Includes

    - Eschericia coli (pathogenic strains)

    - Salmonella

    - Shigella

    - Transmission route: Fecal-oral route

    * E.coli K-12 MG1655 Cells.

    Stationary phase cells .


Materials and methods1
Materials and Methods

  • Multi-parameter flow cytometry


Materials and methods2
Materials and Methods

  • Fluorescence stain


Results
Results

  • Culturability


Results1
Results

Aerobic incubation VS. Anaerobic Incubation



Results3
Results

  • Total [ATP]


Results4
Results

  • Efflux pump activity


Results5
Results

  • Membrane Potential (Depolarization)

Fig 5 d-f

Fig 4 e


Results6
Results

  • Membrane Integrity

Fig 5 g-i

Fig 4 f


Results7
Results

  • Glucose uptake ability


Results8
Results

  • Syto 9 vs. Culturability


Results9
Results

  • Syto 9 vs. Membrane potential (Fig 5e & h)


Discussion
Discussion

  • Inactivation Pattern

[ATP] decrease

Inactivation of Efflux pump

Loss of Culturability

Loss of membrane potential

Glucose uptake rate decrease

Loss of membrane integrity

Bosshard et al.,2009


Discussion1
Discussion

  • Subsequent dark storage of Salmonella typhimurium

Bosshard et al.,2009


Discussion2
Discussion

  • Subsequent dark storage of Shigella flexneri

Bosshard et al.,2009


Discussion3
Discussion

  • Inactivation mechanism

  • Rapidly [ATP] and inactivation of Efflux pump activity

     Due to damaged on respiratory chain

     PyKF (Pyruvate Kinase) is a direct target


Discussion4
Discussion

Repair and regrowth

- Viability test were carry out 5 days after irradiation.

 No regrowth or recovery.

 Significant decrease in all measured cellular functions

** This indicates that damaged that caused by UVA light is irreversible.

**The re-grown of permeabilized cells has never been shown


Conclusion
Conclusion

  • SODIS and artificial UVA light kill enteric bacteria by inactivation of the respiratory chain and subsequent exhaustion of ATP.

  • Split exposure reduce the light dose required for inactivation.

  • Temperature is not a predominant factor in the SODIS method.



References
References

Michael Berney, Hans-Ulrich Weilenmann, and Thomas Egli Flow-cytometric study of vital cellular functions in Escherichia coli during solar disinfection (SODIS) Microbiology, Jun 2006; 152: 1719 - 1729.

F. Bosshard, M. Berney, M. Scheifele, H.-U. Weilenmann, and T. EgliSolar disinfection (SODIS) and subsequent dark storage of Salmonella typhimurium and Shigella flexneri monitored by flow cytometryMicrobiology, April 1, 2009; 155(4): 1310 - 1317.

Kenya Sun Water Safer to Drink CNN. David McKenzie. September 1, 2009 <http://edition.cnn.com/video/?/video/world/2009/09/01/mckenzie.sun.water.cnn>

SODIS. “SODIS (short for Solar Water Disinfection)" <http://www.sodis.ch>


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