Madeleine Schouman
Pronouns: she/her
Research Mentor(s): Mia Howard
Research Mentor School/College/Department: Ecology and Evolutionary Biology / LSA
Program:
Authors: Madeleine Schouman, Mia Howard
Session: Session 4: 1:40 pm – 2:30 pm
Poster: 51
Abstract
Our expanding appreciation of the plant microbiome creates a growing need to experimentally manipulate plant-microbe interactions. However, microbial contamination is a major challenge of conducting plant-microbe experiments, especially with the large numbers of experimental units typically needed to ask ecological and evolutionary questions. One particularly tricky group of microbes are rhizobia, bacteria that form mutualistic relationships with legume species by fixing atmospheric nitrogen and converting it to ammonia–a form the plants can use. In return, the plant provides the rhizobia with carbohydrates and shelter within the nodules. However, this bacteria’s ability to spread via water, soil, and air can lead to rampant contamination within microbe experiments. Previous studies have found that clovers (Trifolium spp.) experienced 175-200% higher rhizobium contamination rates than 17 other legume species grown in the same conditions. This proclivity to form symbioses with rhizobia makes the clover-rhizobium system a convenient model to evaluate the methods of microbial containment. Scientists have employed the use of a variety of methods to prevent microbial contamination in plant-microbe experiments; however, the efficacy of these strategies has not been compared. Our experiment seeks to evaluate the performance of containment methods in differing plant growth environments. The first location of this study was a growth room fitted with a drip irrigation system to minimize contamination through water splashing between pots. In this environment, we tested the following containment methods: sand (this produces a barrier on top of the soil), doubling up pots (prevents water from splashing up from the bottom), bottom watering (watered from a sealed container beneath the pot, preventing splashing and microbes entering through the bottom of the pot), sand with bottom watering, doubling up pots with sand. The second part of the experiment was conducted at the Matthaei Botanical Garden’s Greenhouse where the plants were kept in a shared space and routinely irrigated with mist. We plan to harvest the plants after 6 weeks and examine the roots for rhizobium nodules. The containment methods with the fewest rhizobium nodules will indicate the most effective strategy for preventing contamination. We hope that our results will help scientists researching plant-microbe interactions reduce contamination in their studies.
