Common Essential Oils and E. Coli Growth Inhibition

Austin, Steven

Section E

Seat 5B

Common Essential Oils and E. Coli Growth Inhibition

Introduction

Bacteria are one of the most common organism on this planet. They are part of the kingdom Monera, and are also thought to be one of the most ancient organisms. One of their most distinguishing characteristics is their unicellular structure. There are several chemicals that people use in their households to eliminate bacteria.

In this experiment, different household oils will be tested for their effiency in inhibiting bacterial growth. The hypthesis is that none of these oils will have a significant effect on the zone of bacterial inhibition.

Methods

Forceps were soaked in rubbing alcohol before use to prevent cross-contaminatin. A dilute culture of E. coli bacteria was spread on the surface of an agar plate, and sat at room temperature for 20 minutes. The plate was divided into six equal divisions from the center. Six discs of filter paper were each soaked individually in one of six chemical oils: tea tree, sweet fennel, red thyme, bue eucalyptus, sweet basil, and canola oil. They were placed equidistant from each other in a concentric circle within the plate, using the forceps. The plate was taped shut, labeled by bench and section, and refrigerated at 37Ñ"C in an enclosed bin for 24 hours. Plates were then moved to a refrigeration temperature Afterwards, storage temperature was altered to 4Ñ"C for the remainder of the time before the next lab, approximately six days. Zones of inhibition were measured on the underside of the plate, where the immediate opposite was coated with the bacteria, with a ruler.

Results

Only three of the oils used in the experiment registered noticeable results. The tea tree oil had a zone of inhibition of 17mm; red thyme had a zone of 20. The smallest of these zones was made by canola oil at only 7mm. The graph more specifically shows the diameters of the zones in relation to one another.

Solution Inhibition Zones

Inhibitor Solution Zone of Inhibition (mm)

Tea Tree Oil 17

Sweet