Marazzano Colon
Year: 2018
Faculty Advisor: Fay-Wei Li

“Nitrogen fixing symbioses in bryophytes show host preferences between cyanobionts”


Project Summary:

Nitrogen is important for all plants but it is often a limiting nutrient because plants cannot directly metabolize the nitrogen gas that composes 78% of the earth’s atmosphere. (Goyal et al. 2005). In order to obtain nitrogen when not enough is available in the soil, certain plant species have developed symbiotic relationships with bacteria that fix atmospheric nitrogen, converting it into compounds the plants can process. The most ancient origin of bacteria-plant nitrogen fixing symbiosis is that of the hornwort-cyanobacteria symbiosis.  Hornworts are one of the three lineages of bryophytes—hornworts, liverworts, and mosses—all characterized by their gametophyte dominated life cycle, lack of vasculature, and preference for moist cool habitats. Within the bryophytes, all hornworts and two liverwort species can form symbiosis with cyanobacteria. The cyanobacteria, mostly in the genus Nostoc, live in mucus cavities in the plants. Studying this symbiosis will help elucidate the evolution of nitrogen fixing symbioses in plants. Our study investigates the variation in symbiosis between different pairings of cyanobacterial strains and bryophyte hosts grown in microcosms. In this experiment we inoculated sterile plants of the four bryophyte species Anthoceros punctatus, Anthoceros agrestis, Blasia pusilla, and Dendroceros sp., with two cyanobacteria of the Nostoc genus: Nostoc punctiforme and an unidentified Nostoc species. We measured the growth rates of the plants and how many colonies the cyanobacteria formed in the hosts. Although the cyanobacterial strains did not affect host growth, colonization rates consistently differed between the two Nostoc strains, demonstrating host preferences between symbionts.

My Experience:

A transformative experience is how I would dub this internship. The best part of it is was not what I learned about PCR mixes, bench work, Acetylene Reduction Assays, primer design, non-vascular plant taxonomy, or any number of new lab techniques, but what my fellow interns and co-workers taught me about what it means to carry out science and gain knowledge from it. The passion that I saw science fueling in the eyes of people around me allowed me to realize how much it enriches the lives and spirits of those who choose research as their purpose. Listening to the practical and scientific wisdom of my peers, mentors, and co-workers taught me many things I did not know existed. This experience has made me more passionate to learn in academic research settings and continue doing science!