Bacteria Growth Lab

Purpose:  The purpose of this lab is to observe the growth of bacterium under different conditions.

  Bacteria used: sarcina aurantiaca

Materials:

3 plates of nutrient agar

tape

tweezers

regular paper

sterilized paper

lysol

soap

hole puncher

bunsen burner

Procedure:

-Divide 2 of the plates of nutrient agar into 4 quadrants each; one with ABCD, the other with EFGH

-ABCD are samples around the school with D being a control (just tape, sampling nothing)

-EFGH: E is soap, F is Lysol, G is paper, and H is sterile paper

School Sample

-Wash hands, then wrap tape around finger, use the part of the tape that has not touched anything and lightly touch the surface you want to test (do this three times on three different surfaces while taking pictures/drawing the place of sampling)

-open the plate slightly and lightly touch the tape on the agar (nutrient substrate that feeds bacteria)

-take a piece of masking tape and seal the plate (plate ABCD); DO NOT OPEN THE PLATE AGAIN!

-take pictures and analyze the results

-keep the plate in warm room and not in optimal conditions

Aseptic Technique Sample

-light a controlled fire (eg. Bunsen burner)

-put the loop over the Bunsen burner to sterilize it (kill all bacteria) until it is red hot, then let it cool before sticking it into the sample of bacterium; DO NOT TALK WHILE LETTING IT COOL and do not let it touch anything else

-also sterilize the tip of the test tube very lightly

-do not touch the sides of the test tube

-take the known sample of bacterium (sarcina aurantiaca) and inoculate the loop with the bacteria

-take the loop and make back and forth S shapes on the agar plate (draw out)

Aseptic Technique + Quadrants (EFGH) sample

-draw quadrants on agar plate

-follow all steps for “aseptic technique sample”

-as mentioned above, E is soap, F is Lysol, G is paper, and H is sterile disk

-sterilize tweezers over the controlled fire (do not go red hot since the entire thing is metal)

-hole punch regular paper and put one in the beaker labelled Lysol

-try to use proper sterile technique (don’t touch the table, don’t set the tweezers down, etc)

-put the paper (Lysol) on quadrant F

-put the paper with NOTHING on it on quadrant G

-on quadrant H, sterilize the tweezers and pinch out a sterilized piece of paper from a test tube

-on quadrant E, put soapy water on it, but not agitating it (no mechanical part, meaning no rubbing)

Data and Observation

A: Mr. McCallian's Doorknob

B: Vending Machine Buttons

C: Cafeteria Table

D: Control ( tape itself)

Results: There was bacterium growth in quadrant B and C, and no growth in A and D