Cultivation and Isolation of Chemolithoautotrophic Microorganisms

Preethi working in lab




Assistant Professor and Elliman Faculty Fellow

Project Summary

This summer I worked under the guidance of Dr. Ileana Pérez-Rodríguez, whose research includes a study on the use of iron reducing microorganisms in the treatment of asbestos to reduce the hazards they pose to the environment. My work centered around the enrichment and isolation of methanogenic and iron reducing microbes from deep sea hydrothermal vents in the Pacific Ocean. Organisms that could dwell in these regions include thermophiles, methanogens, acetogens, iron reducers, and more. Less than 1% of all of species of microorganisms present on earth have been identified, and an even smaller percentage of those have successfully been grown and studied in a lab setting. The purpose of this project was to cultivate growth of the microorganisms taken from hydrothermal vent samples, then isolate and identify strains, and if possible, to add to the existing culture collection of known organisms.

Through the work I did, I learned a great deal about the practices necessary for the growth and cultivation of anaerobic microorganisms. This was incredibly eye-opening, as every technique I learned in growing the cultures continually emphasized the stark contrast from the cultivation practices of aerobic microorganisms that I have used in the past. The tolerance to oxygen is the primary difference between these two types of microbes, but this difference affects almost every single aspect of cultivation for each, and is also the reason for the discrepancy in complexity of techniques used. While I have worked in biology labs before, the work I have done this summer has demonstrated just how diverse the experiences can be across the many sectors of a single scientific discipline, despite how similar the principles behind the protocols may be. It also illustrated how simple biological principles at the microscopic scale have a great impact on the science and technology used at the macroscopic scale in studying them.


Additionally, I learned principles of microscopy – used to investigate both the growth and nature of the microorganisms being studied. Finally, I experienced the process of conducting a hydrothermal vent microbiological isolation from start to finish. The technique of enrichment culturing was used to select for a specific type of microorganism within the mixed environmental samples. By setting the conditions of growth (i.e. temperature, growth medium, nutrient type, etc.) favorable to a target type of organism, selection was conducted. Subsequent rounds of isolation, through a dilution series, were performed until a single morphology of microbe was observed. DNA sequencing was used to determine whether the microorganism cultivated was one that has already been identified, or whether this was the first instance of it having been isolated on record.


Thank you to the Penn Undergraduate Climate Action Grant I received from CURF that allowed me to have these experiences and learn about microbiology theory and practices.