USING TEM TO HELP UNDERSTAND THE RELATIONSHIP BETWEEN ARAGONITIC CRYSTAL GROWTH AND ORGANIC COMPOUNDS

The relationship between microbes and crystal growth has been a debated topic among scientists. The objective of this project is to test the hypothesis that organic molecules not only act as a substrate but also promote crystal growth. Precipitation experiments were conducted to grow calcite and aragonite crystals among different common organic molecules like palmitic and urease acid. Palmitic and urease acids were chosen because they are found in biofilms. Palmitic and urease acid also create spherical to subsperical organic shapes similar to those found at the base of aragonitic botryoids, which are believed to be organic compounds acting as a substrate. Nonorganic precipitation experiments were also conducted with glass cullet for comparison. Samples were precipitated between 12 and 72 hours. Samples were studied in thin section, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). TEM analysis helps show a clearer transition from organic material and crystal growth. The samples showed spherical to subspherical structures at the base of crystal growth. These spheroidal structures may be calcium carbonate proto-crystals or organic compounds serving as an substrate for the aragonite and calcite crystals. Though still circumstantial, evidence suggests a relationship between organic molecules.