Summer Update

This summer at the Friesen Lab we have all been extremely busy! Dr. Friesen was in Europe until last week collecting Medicago polymorpha so it was up to the rest of us to keep the laboratory productive in her absence. We have a few new summer interns, which makes the lab a full house but we are happy to have them! From the Plant Genomics REU program, Nayeli is working with Colleen on characterizing novel bacterial isolates from various Trifolium species collected at the Bodega Bay ecological research site in California. From the Summer Research Opportunity (SROP) program, Carla is working with Dr. Chandra Jack to determine the effects of herbivory on native and invasive Medicago polymorpha. We also have two new high school students from HSHSP: Matt, who is mentored by Colleen, is researching the potential benefits of mixed nodules in Medicago plants that are inoculated with a fixing and a non-fixing variety of the same strain of rhizobia and Amy, who is being mentored by Dr. Jack, is using Medicago polymorphaEnsifer medicae, and Chrysodeixis includens to test the Novel Weapons Hypothesis.

In addition to mentoring students this summer, Colleen is working to parameterize a mathematical model of the carbon/nitrogen trade between legumes and rhizobia. She is growing plants over a carbon and nitrogen gradient and examining how their allocation to acquiring resources and the symbiosis changes across the gradient. Prateek is conducting a study to understand gene expression profiles of plants under different competition regimes—it will also be extrapolated to see if rhizobacterial members are affected by changes in exudation and gene expression profiles. He is also trying to identify how changes in resource complexity and abundance impact digital microbiomes using Avida. *Ellie has not submitted a statement*

As for the undergraduates, I am here full time; we also have Duncan and Megan who are working on maintaining our greenhouses, seed stock and Medicago experiment. Starting soon, we will have a new laboratory technician starting on DNA extractions from our various harvests. We have a new rotating graduate student, Shawna, who was a member of SROP in our lab last summer. Dr. Chandra Jack is away at the evolution conference in Brazil and will travel to Europe after that for another conference. Dr. Jeff Norman is continuing his work culturing oxygen-tolerant free-living N fixers from a diverse array of environments in line with the goals of the Nitrogenase project.  He is also currently using stable isotope probing to identify the organisms that fix nitrogen in natural systems and will soon be starting work to investigate biogeochemical controls over free-living nitrogen fixation as well.

Our large greenhouse is now fully functional and is equipped with an automatic misting system and catchment apparatus for easy runoff decontamination. The misting system is modeled after a system set up by our collaborator, Stephanie Porter, at University of California-Riverside. We have been tweaking it for our own use since January 2015. Now that we have it set up, we won’t have to worry about introducing contamination to our plants because they will be watered by the system. The misting runoff that could contain foreign rhizobial strains is now being funneled into a tank under the benches where it can then be bleached and safely disposed of.

One of the three benches in our new greenhouse; complete with automatic misting system!

One of the three benches in our new greenhouse; complete with automatic misting system!

One of the largest experiments we currently have in the greenhouse consists of 800 pots of Medicago polymorpha and lupulina. The goal of this experiment is to collect phenotype data, and perform Restriction site Associated DNA (RAD) sequencing to determine the community structure of native and invasive genotypes. Strains from nodule contents of the Bodega harvest are still being grown up and put into freezer stocks. After PCR confirmation of rhizobial strains, these strains of wild invasive region (CA) rhizobia will be useful for our lab’s future experiments.

In late-July, I will be traveling to Minneapolis, MN for the American Society of Plant Biology (ASPB) conference with Colleen and Dr. Friesen. This trip is funded by a Bio-REU travel grant from the National Science Foundation. I will be presenting a poster titled “Assessing rhizobial dependence of Medicago polymorpha as it evolves in non-native regions,” which was a project from spring semester. I recently set up another experiment to further investigate how native and invasive genotypes interact with different sets of soil microbes for the greatest growth benefit.