Presentation is loading. Please wait.

Presentation is loading. Please wait.

Experiment three Physical and Chemical agents for the Control of microorganisms Effect of Ultraviolet Radiation Effect of chemical agents.

Similar presentations


Presentation on theme: "Experiment three Physical and Chemical agents for the Control of microorganisms Effect of Ultraviolet Radiation Effect of chemical agents."— Presentation transcript:

1 Experiment three Physical and Chemical agents for the Control of microorganisms Effect of Ultraviolet Radiation Effect of chemical agents

2 Effect of Ultraviolet Radiation
Ultraviolet radiation (UV, nm) The most effective wavelengths: 265nm Mechanism: destroy bacteria by interfering with DNA replication and transcription during protein synthesis Characteristics: poor penetration damage of the eyes and the skin.

3 Effect of Ultraviolet Radiation
MATERIALS: Media: Nutrient agar plate Culture:18-24 hours cultures of Escherichia coli Alcohol burner , inoculating loop, cotton swab .

4 Effect of Ultraviolet Radiation
PROCEDURE: Take a nutrient agar plate, streak E.coli intensively on the plate. Place the plate directly under the ultraviolet lamp. The plate lid cover half part of the agar surface. After exposed to ultraviolet light for 30minutes,close the plate.Incubate the plate in an inverted position at 37℃ for 18 to 24 hours and observe the results. RESULT: Observe the growth of bacterium in the plate. .

5 Effect of chemical agents
Mechanisms of action -- Destroy cell membranes; e.g., surfactants/detergents -- dissolve lipids -- Denature bacterial proteins (e.g., enzymes ); Interfere bacterial metabolism -- Damage genetic materials (DNA, RNA); e.g., formaldehyde.

6 Effect of chemical agents
Commonly used chemical agents ---Phenol ---Soaps and detergents ---Alcohols: 70-75%(medical use) ---Heavy metals: Silver nitrate (1%) ---Chlorine ---Iodine ---Aldehydes: 37%, Formalin ---Dyes: crystal violet

7 Effect of chemical agents
Reagents: 1. 1% crystal violet 2. 2% mercurochrome 3. 5% iodine 4. 0.1% bromogeramine 5. normal sodium Species: S.aureus agar plate E.coli agar plate

8 Effect of chemical agents
PROCEDURE: Using Sterile techniques, incubate the agar plate with the culture of S.aureus (or E.coli) by streaking the agar plate in horizontal and vertical directions with an inoculating loop Using a flamed and cooled forceps, take each saturated disc and place it in the appropriately labeled area respectively to ensure that each one ie at the middle point of radius and of them are equidistant from each other. Gently press each disk down so that they adhere to the surface of the agar. Label and incubate all plate culture in an inverted position at 37℃ for hours.

9 iodine normal sodium bromogeramine mercurochrome crystal violet

10 Effect of chemical agents
RESULT: Measure inhibition zone – diameter or 2× radius

11 Diameter of Inhibition Zone (mm)
Inhibition zone diameter (mm) >15mm 10~15mm <10mm 0mm susceptibility degree Extremely sensitive Medium sensitive Slight sensitive restistant Record: Cultures Diameter of Inhibition Zone (mm) crystal violet mercurochrome iodine bromogeramine normal sodium S.Aureus E.coli Susceptibility degree

12 Thank!


Download ppt "Experiment three Physical and Chemical agents for the Control of microorganisms Effect of Ultraviolet Radiation Effect of chemical agents."

Similar presentations


Ads by Google