The Quick and Dirty: Endospore Verification in Our Unknown Bacterium

       Several types of bacteria are known to form tiny versions of themselves when the going gets tough. These structures are referred to as endospores, and allow a bacteria to preserve itself when it encounters an environment that is unfavorable for reproduction or is lacking in nutrients. These minuscule spores contain a replicated version of the cell's genetic material, several types of ribosomes, and a chemical known as dipicolinic acid, which helps the endospore remain in its dormant phase. Endospores are extremely difficult to destroy or "kill." They can survive the most extreme of conditions: extremely high or low temperatures, ultraviolet radiation, extremes in pH, and even excessive drying. What's more, endospores of some species can survive for centuries or even millennia (hopefully nowhere near my house)! The evolutionary acquisition of bacterial endospores was probably favored in species that were often exposed to nutrient-lacking or high stress environments. Some bacterial cells may not have not evolved the ability to produce endospores simply because they did not often encounter these types of environments and, thus, it would not have been energetically favorable to do so.

     In this week's experiment, we performed an endospore stain to further narrow the possible identities of our microbe. Cells lacking endospores should appear light pink in color following the stain. Cell containing endospores should contain darker blue structures much smaller than the larger pink cells when examined under a microscope. Because endospores are able to tolerate extremes in temperature, we also performed a heat shock on a sample of our unknown bacterium. If growth was observed several days following the heat shock, it would indicate that endospores were present in the sample.

     As seen in the picture to the right, growth was observed in both the heat shocked sample (right tube) and the control sample (left tube) and four days of incubation, indicating the presence of endospores in our unknown bacterium. When viewed under a microscope, we saw tiny blue/purple structures scattered across the slide among the larger bacterial cells. These were assumed to be endospores. According to the dichotomous key provided, this opens the possibility that our bacterium could be Clostridium.

http://www.biomedcentral.com/content/pdf/1471-2164-13-265.pdf
http://en.wikipedia.org/wiki/Endospore#Formation_and_destruction

Come back next week for more dirty details!
- Austin