Draft 2/25

This is my lab write for an endospore experiment.

Expected Results:

The expected results were to find gram positive endospores that survived pasteurization at 70 degrees celsius. Isolation of endospores was expected because microorganisms were being isolated from a soil sample. Soil is relatively low in nutrients and nutrient deprivation is what causes endospores to form. Some bacteria have the ability to produce endospores by sporulation. Because endospores are dehydrated (leaving them metabolically inactive) and covered in a thick layer consisting of peptidoglycan and proteins, they are able to withstand high temperatures. The soil samples were pasteurized at 70 degrees celsius in hopes that all vegetative cells would be killed and only protected endospores would be left. The endospores were expected to be gram positive due to their thick peptidoglycan layer, a defining characteristic of gram positive organisms.      

Observed Results:

The pre-pasteurization plate resulted in a lawn. There was no isolation. There were different colored colonies, white, grey, and beige, these colonies were not isolated there was a change in color across the lawn. The post-pasteurization plate resulted in minimal isolation. The were four separate isolated colony types, white rhizoid, white circular (this colony was used for gram stain and phase contrast microscopy), white irregular, and a milky beige irregular colony. After conducting a gram stain and viewing the slides under a light microscope, the stained cells appeared as purple bacilli. The wet mount (which used cells from the same isolated colony as the gram stain) when viewed under a phase contrast microscope resembled bacilli with a circle inside of it. The resulting cells fit the description of a sub-terminal endospore.   

Conclusion:

The observed results were consistent with expected results. Gram positive endospores were expected to be isolated after pasteurization and they were. When observed under a microscope the cells appeared to be sub-terminal endospores. From the performed experiments we can conclude that soil does contain gram positive endospores. We can also confirm that pasteurizing the soil will still result in undamaged endospores demonstrating that they are heat resistant.