Controlling Bacteria

1. Controlling Bacteria

2. Antimicrobial Agents (Bactericide) • Chemical substances that either kill bacteria or inhibit bacterial growth without harming the host

3. 3 Types of Antimicrobial Agents • Antiseptics - chemicals used to inhibit the growth of or kill bacteria on living tissues • Disinfectants - chemicals used to inhibit the growth of or kill bacteria on nonliving things • Antibiotics - compounds that block the growth and reproduction of bacteria

4. How Antimicrobial Agents work • Inhibition of cell wall synthesis • Damage cell membranes • Inhibit the synthesis of DNA or RNA • Inhibit protein synthesis • Inhibit enzyme activity

5. Bacterial Inhibition Lab Level 5 Formal Lab

6. Lab Objective • To test the effectiveness of 3 bactericides • You pick the bactericides you want to test • You need to bring them to class next Monday (except for the antibiotics), small samples

7. State the problem • Write the question that you are trying to answer • Hypothesis • If … then … because • Be sure that your “because” is reasonable • Include name of bacteria being used • Which bacteriacide will be most effective?

8. Bacillus subtilis or E-coli (decide) Petri dish with agar Inoculating loop Bunsen Burner Tweezers Filter paper discs 3 bactericides of your choice (name them) Sharpie marker Parafilm wax Ruler Alcohol Distilled water Incubator Goggles Provided Materials

9. Procedure • Pay attention to the next couple of slides and to the demonstration • Think about the materials provided • Write a logical procedure • Your procedure will be due and checked prior to starting the experiment

10. SterileTechniques • Dip loop in alcohol • Heat loop and wire to red-hot. Flame the handle slightly • Allow the loop to cool for 5 seconds. • Remove a loop full of the organism from the plate by gently scraping the loop against the bacterial lawn.

11. 4. Streak the Plate • Start at edge of the plate (Area A) with a loop full of organism. Spread the organism in one single continuous movement towards the opposite side of the plate. Use light pressure and avoid gouging the agar. • Replace lid • Flame loop and let cool • Obtain another loop full of organism • Start at the opposite edge of plate (Area B) with loop full of organism and spread in continuous movement toward the opposite side of the plate. • Replace lid • Flame loop, let cool, and return

12. Get This Checked Off To Start Lab by next Monday: • Investigative question • Hypothesis • Materials list (Your group supplies antiseptics and disinfectants) • Procedure (logical)- 3 procedures • sterile technique • Streaking • setting up your petri plate • Variables • Data- diagram of plate before (how is it set up), data table for zone of inhibition, picture of plate after (drawn or with camera)

13. How to Measure the effectiveness • Measure the Zone of Inhibition • area around a paper disk or colony of bacteria or mold where no other organisms are growing • measurements are made to quantify the relative effectiveness of a compound

14. Collecting Data Fill in data table: • Find diameter of zone of inhibition • Measure in mm using the ruler • Draw a picture/ or take a picture of your plate, shade in where there is bacteria • Write conclusion (with data #’s as supporting evidence) • Write error analysis • Lab books will be stamped at the beginning of class Monday/Tuesday.

15. How to Measure the effectiveness • Measure the Zone of Inhibition • area around a paper disk or colony of bacteria or mold where no other organisms are growing • measurements are made to quantify the relative effectiveness of a compound