Microbial Biodiversity in Fertilized Soil

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Microorganisms, living organisms too small to be seen with the human eye, include bacteria, fungi, algae, and viruses. These tiny organisms perform important ecological functions, not the least of which is scrubbing the air we breathe of carbon. Biodiversity among microorganisms is often suggestive of the diversity and health of other organisms in an ecosystem. Since the most biodiverse plant and animal populations appear in warm, moist environments such as jungles, for this lab we are going to show that the same holds true for unknown microorganisms on campus or even the microbial populations on students' rucksacks. By taking soil samples from the heavily watered landscaping outside of the Student Union, the tended lawn outside the Student Union, and finally untended soil, we intend to prove that moist, fertilized soil has greater biodiversity than untended soil.


Using a teaspoon, 3 samples were taken from the flower beds in front of the student union. The mulch was cleared by hand then 3 level teaspoons of soil were taken from the top and placed into three separate sterile plastic bags labeled, “Flower Bed.” For our second location, a small patch of grass was removed from the lawn of the student union. 3 level teaspoons of soil were taken from the top of the lawn and placed into three separate sterile plastic bags and labeled, “Lawn.” Finally, a small amount of grass was removed from an untended area near campus and a new teaspoon was used to collect three samples from the topsoil. Each sample was placed in a sterile plastic bag and labeled, “Scrub.”

Three samples were prepared using a dilution and spreading technique. A pinch of soil was taken from each of the three location samples and added to an appropriately labeled flask along with 100ml of water. Each flask was stirred using a glass rod for 5 seconds. Using an applicator, and before the soil settled, three drops of each soil solution were added to appropriately labeled Petri dishes. Each dish was allowed to incubate for 24 hours then was viewed and the contents cataloged under a microscope. This technique was repeated with soil from each of the three locations.


After incubation, results were recorded based on location and sample number. From the Flower Bed1 contained 80% coverage of round smooth masses and smaller cylindrical chains, multiple varied yellow-brown shapes, few fine hair-like structures, 2 crystal-like formations. Flower Bed2 was very similar but no crystal formations were noted. Lawn1 had evenly mixed smooth round and cylindrical chains covering 70% of the petri dish, some larger irregular, smooth shapes, and one branched, hair-like structure. Lawn2 slightly less coverage of smooth round and cylindrical chains, some larger irregular, smooth shapes, 3 branched hair-like structures. Scrub1 had the highest proportion of large, smooth irregular shapes, but only 40% coverage cylindrical chains, and fewer smooth round chains. No hair-like structures were identified. No difference could be seen between Scrub1 and Scrub2.


Sample data indicates that that the moist, cultivated soil in the flower bed is the most biodiverse, showing the most growth overall, and most individual types of growth. The round and cylindrical chains appear to be bacteria, and the hair-like structures resemble fungi. The lawn, which appears to be regular watered, showed nearly as much growth overall, with a similar level of diversity. The number of colonies of both smooth round, and cylindrical chains are fewer than in the flower bed sample, but still cover the majority of the dish. Finally, the least diverse environment appears to be the Scrub with the fewest colonies and no hair-like structures. The Scrub looks to have the largest proportion of minerals, large irregular shapes. The highest population of bacterial and fungal growth appears in the two locations with the highest moisture, the Flower Bed and the Lawn respectively. The Scrub sample shows higher amounts of minerals and fewer bacterial colonies. Neither scrub sample included the hair-like structures associated with fungus. From this, we can conclude that moist, fertile environments produce the most microbial biodiversity.