The Evolution of Heavy Metal Tolerance Leads to UV Tolerance in Plant Microbial Symbionts
Abstract
Beneficial microbes play a key role in plant health. Rhizobium bacteria are a group of beneficial symbiotic microbes that provide nitrogen to legumes, fertilizing plants. Rhizobia must survive in the soil independently between plant generations. Despite the importance of rhizobia for plant health, little is known about how they adapt to environmental variation in soil. We predict rhizobia from harsher serpentine soils with higher levels of nickel and lower Ca:Mg will have greater UV resistance than rhizobia from more fertile and vegetated soils due to local adaptation to the higher levels of UV irradiation that hit barren serpentine soils. Correspondingly, we predicted that strains with higher tolerance to nickel would show higher resistance to UV irradiation. A total of 179 strains were plated and exposed to ultraviolet light at increments of 0, 12, 24, 36, 48, and 60 seconds to determine their resistance. At eight days, plates were scanned and analyzed to determine the minimum period of exposure to UV required to inhibit growth for each strain. This was carried out in three assays with three replications, resulting in each strain being tested three times. We found that strains with higher tolerance to nickel have higher UV tolerance, while the nickel or Ca:Mg level of the soil does not predict UV tolerance. Therefore, while soil chemistry does not induce local adaptation in rhizobia, we find support for the idea that adaptation to harsh soil chemistry leads to greater UV tolerance in rhizobia, possibly to protect strains from higher UV irradiation.
About the Presenters
Randi Richards
Hello WSU Vancouver Research Showcase goers! My name is Randi, and I am a Biology major currently serving as an intern in the Porter Lab researching plant-microbe mutualisms and their impact on evolutionary processes. I am fortunate to be presenting original research this year, thanks to the lab! I am passionate about both agriculture and microbiology, so this has been the perfect place for me! I am also a member of the ASWSUV Judicial Board and student clubs. So, if you have any questions about campus involvement, feel free to ask!