Day 12: 5/30/14

Discovering our Unknown Bacteria “N”

Today we discovered what our bacteria is. So by using a flow chart we deduced this:

Our bacteria consists of Gram negative facultative anaerobic rods.

The oxidase test turned out negative- it does not have cytocrome oxidase because no electrons were added to the oxidase reagent. Therefore it is an Enterobacteriaceace.

Our bacteria was a strong lactose fermentor- the test proved gas production during lactose fermentation.  It also had a negative test for Indole or tryptophan- our bacteria cannot split tryptophan into indole and pyruvic acid. Because it cannot break down tryotophan it does not use it as a source of energy.

The MRVP test was negative for methyl red and positive for Voges-Proskeur was positive. Methyl red test was negative meaning our bacteria cannot ferment glucose via mixed acid fermentation. The Vogues test showed our bacteria however can ferment glucose.

Now the choices of our bacteria were narrowed down to two ones E. aerogenes and E. cloacae. After battling it out against Peter and Ben we finally claimed E. cloacae as our bacteria and here’s how:

-Our rods are very small- 0.5 to 1.0 to 1.0 to 2.0 microns (as opposed to just small rods for E. aerogenes)

-During fermentation of sugars produced acid and gas actively from glucose and sucrose and less actively from lactose

-Our test was positive for nitrate (meaning our bacteria has a nitrate reductase enzyme)

-Although both of the bacterias were motile, our proved to be more motile than the other bacteria.

-and finally the temperature growth. Our bacteria grew optimally at 30 degrees Celsius.  During the course of the lab it also grew at 37 degrees Celsius when we shared plates with another group. According to the book the temperature for E. cloacae is between 30-37 degrees Celsius.

-the other bacteria E. aerogenes also grows at 30 degrees Celsius, but can also grow at lower temperatures. Peter and Ben’s bacteria grew at 25 degrees Celsius. Therefore after much research and debate, there’s turned out to be E. aerogenes.

FINAL RESULT: Enterobacter clocae

Habitat: in human and other feces and in sewage, soil and water.

Yogurt: 

After letting our yogurt sit for a day we made a fresh yummy yogurt! Because of the active cultures (although there was only one strand) added from the Yoplait yogurt the bacteria grew and multiplied in the milk to form yogurt. Heating the milk beforehand had killed any competing bacteria in the milk and therefore the heated milk had a better result. Delicious!

CAMP: Unfortunately the CAMP test was melted underneath the light, but there was an arrow indicating a reaction and testing positive for S. aureas in Elizabeth.

Well it’s been real, Hope you have enjoyed our blog! Thanks for reading, we had a blast during lab and now our lonely bacteria is no longer unknown! Mission accomplished.