Student Researchers Study Jefferson Memorial Biofilm
About three years ago, rangers working for the National Mall & Memorial Parks (NAMA), a division of the National Park Service (NPS), starting noticing that occasional dark patches on the dome and base of the Jefferson Memorial had begun growing larger and darker. Although the patches looked like the result of smog or perhaps a mold or lichen, they turned out to be a biofilm made of a complex colony of microscopic organisms that adhere to stone surfaces.
In 2014, the National Science Foundation (NSF) launched a study to investigate the biofilms, installing a small weather station on the Memorial’s roof to examine biofilm activity as it relates to environmental conditions. Judy Jacob, NPS Senior Conservator and a member of the NSF study team, spoke to Biotechnology Lab Director Dr. Mary Susan Burnett’s 7th period senior research class about biofilms generally and the Memorial biofilm in particular, and the challenge of simultaneously addressing complex aesthetic and scientific issues affecting such a public structure. She explained how little is known about the biofilm, including whether it contributes to stone deterioration, stone protection, or simply has a benign presence. Answering this question and others will help the NPS — ultimately responsible to the taxpaying public, who will foot the bill for any solution — make a treatment decision.
Earlier that week, three of Dr. Burnett’s Biotechnology Lab students and one student from Lisa Wu’s Oceanography Lab, together with the two Lab Directors, were at the Memorial learning about the biofilm from NAMA personnel and obtaining research samples. NAMA staff explained why the problem will likely take some time to resolve: Power washing removes surface material, laser ablation is time-consuming, and biocides leave an orange residue. Moreover, no treatment offers a permanent solution. Before trying other treatments, the staff would like to better understand what they’re dealing with.
Enter TJ researchers. After reading about the biofilm in the paper, Mark Hannum, TJ Neuroscience Lab Director and Science & Tech Division Manager, connected his friend Jennifer Epstein, NAMA Education Specialist, with Dr. Burnett. Epstein introduced Dr. Burnett to Jacob, who in turn introduced her to Dr. Federica Villa, the NPS project microbiologist based in Milan who is now advising the student researchers.
Twelve of the thirteen students in Dr. Burnett’s 7th period class will be working on some aspect of the biofilm project. “This reflects the way science is done in a typical research lab, where members work collaboratively on various sub-projects related to one or two larger research areas,” she said. She envisions that some projects will extend over multiple years.
Possible projects include:
- Comparing samples from various parts of the memorial (the group hopes to get samples from the dome on a future visit) to see how the composition varies;
- Collecting samples from the air surrounding the biofilm to compare the air microbiome with the biofilm on the marble (one theory connects increased growth of microorganisms with lower air pollution levels; pollen from Tidal Basin cherry trees is another potential contributing factor);
- Attempting to grow the substance in the lab in order to better understand its character; and
- Experimenting with disabling the biofilm’s pigment production so it could no longer turn black.
Students will use TJ’s confocal microscope, recently purchased with Campaign for TJ funds, to examine collected and lab-cultured samples, and the Thermo-Fisher ion torrent Personal Genome Machine, purchased earlier, to identify the various microbial species present in the biofilm as well as their relative abundance. Dr. Burnett anticipates needing several additional pieces of equipment, as well as supplies, to support the work, including a bioreactor to grow a simplified version of the biofilm in the lab, and an impinger, which allows the collection of airborne microorganisms.