Plant-microbe interactions

Azolla ferns

Photo of some  Azolla  strains in growth-chamber culture.

Photo of some Azolla strains in growth-chamber culture.

I am developing the aquatic fern genus Azolla into a model system for studying the causes and consequences of host-symbiont coevolution. All Azolla species host endosymbiotic Nitrogen-fixing cyanobacteria which are transferred from parent to offspring. With funding from the DOE Joint Genome Institute and US Department of Agriculture, am sequencing the genomes of this cyanobacterial symbiont and other undescribed microbial taxa, across the entire host genus to investigate the timing and order of genomic adaptations to endosymbiotic lifestyles. I am also be performing reciprocal transplant experiments to identify the the fitness consequences of disrupting long-term cospeciation dynamics. Future studies will also focus on the role of symbiotic N-fixation on the development of aquatic food webs, and on the roles of symbiotic bacteria in plant-herbivore and competititive interactions.

With the aid of the Dr. Cecilia Koo Botanic Conservation center in Taiwan, I am growing a large collection of georeferenced Azolla strains from the germplasm collection previously housed the International Rice Research Institute in the Philippines. If you are interested in obtaining any strains from this collection for research or education purposes, I would be happy to be of service.

Pitcher plants

A primary goal of my disseration research was to demonstrate links between changing microbial communities and the functioning of their ecosystems (or hosts). To accomplish this, I studied how microbial communities develop and change over time within the digestive leaves of the carnivorous pitcher plant Darlingtonia californica. This unique plant relies on a microbial food web to break down captured insect prey in a manner somewhat analagous to our own microbiota. My research entailed enumerating all compartments of pitchers' communities (viruses, bacteria, protists, & arthropods) and linking their dynamics to rates of carbon and nitrogen mineralization using stable isotope tracers and respirometry. My results indicated strong associations between community turnover, biomass degradation, and host nutrient uptake.