Controlling Bacteria

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

3 Types of Antimicrobial Agents 1.Antiseptics - chemicals used to inhibit the growth of or kill bacteria on living tissues 2.Disinfectants - chemicals used to inhibit the growth of or kill bacteria on nonliving things 3.Antibiotics - compounds that block the growth and reproduction of bacteria

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

Bacterial Inhibition Lab Level 5 Formal Lab

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

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?

Provided Materials 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

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

SterileTechniques 1.Dip loop in alcohol 2.Heat loop and wire to red-hot. Flame the handle slightly 2.Allow the loop to cool for 5 seconds. 3.Remove a loop full of the organism from the plate by gently scraping the loop against the bacterial lawn.

4. Streak the Plate a.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. b.Replace lid c.Flame loop and let cool d.Obtain another loop full of organism e.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. f.Replace lid g.Flame loop, let cool, and return

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)

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

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.

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