Exploring the bacterial endophyte communities of Lycopodiaceae
Plant-microbe interactions have been instrumental to plant ecology since the first plant terrestrialisation over 400 million years ago. Endophytes, defined as microbes living within healthy plant tissue, can increase host plant competitive fitness, confer resistance to biotic and abiotic stress, and promote growth by producing phytohormones or providing essential limiting nutrients. Lycophytes are the earliest diverging extant lineage of vascular plants and evolved roots independently from the other vascular plants (ferns and seed plants); roots are an important entry point for endophytic microbes. The lycophyte microbiome has been scarcely characterized, leaving a significant knowledge gap both in the evolution of plant-microbe interactions and in the biochemistry and ecology of lycophytes. Many lycophytes are under conservation status and some species (Huperzia spp.) produce Huperzine A, a compound with potential application as an Alzheimer’s medication. Understanding the microbiome would lend insight to explanations of lycophyte distribution patterns and biochemical properties, aiding conservation and medical applications.
We collected samples of five species in the family Lycopodiaceae from a single population at Shindagin Hollow State Forest near Ithaca, New York: Lycopodium clavatum, Dendrolycopodium dendroideum, Spinulum annotinum, Huperzia lucidula, and Disphasiastrum digitatum. We surface sterilized plant segments of different tissue types, plated them on LB agar, and isolated single bacterial colonies that grew. We then amplified and sequenced the 16S region (primers: 27F and 1492R) of each bacterial isolate to identify bacterial taxa. Overall, the most frequently occurring bacterial genus was Bacillus followed by Paenibacillus. The greatest isolate count and bacterial diversity was found in H. lucidula. Subterranean tissue samples produced over twice the number of isolates as aerial tissue samples. With taxa abundance data, we utilized biodiversity and similarity indices to determine host and tissue specificity. Based on previous research, the bacterial endophytes identified include known plant-growth promoting rhizobacteria, phytopathogens, root-associating and endophytic diazotrophs (nitrogen-fixers), and bacteria that confer stress tolerance to their hosts. Future research could look into the specific roles of these bacteria in lycophyte ecology or perform more extensive analyses to identify phylogenetic patterns in the evolution of lycophyte-microbe associations.
These past two months at BTI have been some of the shortest months of my life. I think it has felt this way because my time has been filled with doing interesting research, making new friends, learning new things through various BTI-sponsored activities, and exploring a part of the country I have never been before. Life has been a beautiful balance between taking strides to achieve life goals and having a good time along the way. As my first research position, working in the Fay-Wei Li lab taught me what science in action is like: the trial and error, the repetition, and the feeling of satisfaction when you get results that mean something. I experienced just how much researchers know about their field and the ways that they are actively expanding it. Before this internship, I was on the fence about whether or not I wanted to attend graduate school. Now, I am confident in my desire to continue researching the things that inspire fascination in me as well as have the potential to help people and our environment. Being at BTI has made my next steps in life clear to me: I am going to take a gap year after graduation to gain more research experience before attending graduate school in a field of the environmental sciences.