Week 2, Day 5

 May 24, 2013

After settling into lab, we retrieved our test tubes. Our gelatin and litmus milk tests still needed more incubation time, and our carbohydrate tests were still negative. We moved on to making our hanging-drop slide to check the motility of our bacteria. We transferred a small drop from our broth culture onto a disc cover slip and applied the disk to a clear slide. We examined the slide under the microscope using immersion oil and were able to make our small bacteria moving around inside the droplet. This matched the results of our motility test from the days before, where we were able to make out small jagged zig-zagging patterns around where the inoculating needle had stabbed through the agar.

After replacing our microscope and returning the remaining samples to the incubator, we cleaned-up and took a break from lab. We returned an hour later and began working on our oxidase test to determine if our bacteria has cytochrome oxidase, a particle in electron transport during respiration. We transferred some of the bacteria from our oxidase slant to a sterile cotton swab and added 10 drops of oxidase reagent to the swab. A few purple spots began to appear on the swab, indicating a positive test. 

Oxidase Reagent

Oxidase Slant

Cotton Swab (Positive)

Before we left we examined our thioglycolate test tube and were able to identify our bacteria as being an aerobic bacteria. After this we cleaned our stations and hands before taking our lab coats off and leaving the lab for the day.

Thioglycolate Tube (Aerobic)