University of Miami Coral Gable, Florida, United States
Background/Question/Methods
Locally-adapted microorganisms can help plants tolerate more stress and, consequently, extend the plant’s geographic range. Through core and accessory genes in a pangenome, microbes, their adaptive genes, and potential plant-growth-promoting properties can be identified. Accordingly, the genetic basis and distribution of local-adaptation in microorganisms remains to be explored. With its elevated concentrations of heavy metals, high magnesium to calcium ratios, and low-water holding capacity, serpentine soils exert a strong selective pressure on inhabiting plants and microorganisms. While some plants are endemic to serpentine soil, most plants are unable to survive on serpentine soils. Serpentine-indifferent plants are able to thrive both on and off serpentine soil and our previous research has shown that associations with locally-adapted plant-growth-promoting bacteria may be partially responsible. Using whole-genome sequencing, culture-dependent physiological assays, and manipulative plant growth experiments, our project aims to 1) identify genes related to local adaptation to serpentine soil, 2) characterize the variation of plant-growth-promoting properties associated with microorganisms isolated from serpentine and non-serpentine soils across California, and 3) correlate the presence of genes and plant-growth-promoting properties to outcomes in plant development. Serpentine and non-serpentine soil were collected from 23 paired sites across California and 272 isolates were cultured from these soils.
Results/Conclusions
About 50% of isolates from each soil type have the ability to fix nitrogen, and about 20% from each soil type can solubilize phosphorus. The whole-genomes from 93 free-living nitrogen-fixers are currently being sequenced and we expect to see a greater abundance of genes related to magnesium transportation and nickel efflux in isolates from serpentine soil compared to those from non-serpentine soils. Furthermore, we expect plants to develop longer and more complex root systems when associated with microorganisms that have genes that indicate adaptation to serpentine and plant-growth-promoting properties. Results from this project have the potential to provide basic information concerning nutrient cycling in metal-rich and drought-prone soils and have implications for basic science in plant-microbe interactions as well as applications in agriculture and bioremediation.
