Alexadria Igwe Will Work on Soil Microbial Communities

UC Davis doctoral student Alexandria “Allie” Igwe, advised by community ecologist and assistant professor Rachel Vannette of the UC Davis Department of Entomology and Nematology, has received a prestigious $138,000 National Science Foundation Postdoctoral Fellowship to work on soil microbial communities and develop novel online tools to increase interest in ecology.

Igwe who joined the UC Davis doctoral program in 2015, anticipates receiving her PhD in microbiology in September 2020.  Her thesis: “Microbial Community Contribution to Plant Abiotic Stress Tolerance: A Case Study in Serpentine Soils.”  Igwe focuses her research on plant-microbe associations, microbial ecology, environmental microbiology and bioinformatics.

“Plant-microbe associations impact plant phenotype, distribution and biodiversity and range in their effects on a continuum from costly parasitic to beneficial mutualistic interactions,” she wrote in her successful proposal. “These mutualistic relationships also range from loose and facultative to endosymbiotic and obligate. The relationship between nitrogen-fixing bacteria and plants is especially important ecologically. Research into these associations have traditionally focused on endosymbiotic relationships within the nodules of legumes. I propose to explore the impact of strong selective soil pressures on microbial local adaptation and mutualism using free-living nitrogen-fixers and non-legumes.“

“My study,” she wrote, “will utilize serpentine ecosystems because serpentine soils are naturally high in heavy metals and deficient in plant nutrients which contributes to low plant productivity and presents strong selective pressures. The system also includes a free-living nitrogen-fixer, Microvirga spp., and plants that can grow on both serpentine and nonserpentine soils (serpentine-indifferent), allowing tractable manipulations across stress environments. Research with this system can be useful for disentangling the relative influence of soil and plant type on the establishment of mutualistic relationships and its impact on plant performance.”

gwe plans to use “culture-based isolation techniques, qPCR, whole-genome sequencing, and manipulative greenhouse and field surveys to: (1) Quantify the abundance of Microvirga spp. in serpentine and nonserpentine soils and explore the relative influence of edaphic factors, elevation, and climate on bacterial abundance. (2) Identify the presence of ecotypic variation in serpentine- and non-serpentine-isolated Microvirga spp. using functional assays and genome-wide sequencing, and (3) Determine the effect of Microvirga spp. on non-leguminous plant survival and development.”

She seeks a career as an environmental microbiologist to “scientifically and commercially address problems related to environmental degradation and food security.”

 “Allie has initiated exciting research directions during her time in the lab: examining how rhizosphere microbes influence plant survival and growth on serpentine soils,” said Vannette, a UC Davis Hellman Fellow.   “She has funded this work through several successful grant applications during her graduate career at UC Davis. Her creative research suggests previously unrecognized ways that plants are able to successfully establish and grow on harsh soils. She has also found that the composition of soil microbes can affect seedling establishment and also change when plants flower!”

“Her findings are novel and they are already making an impact on the field,” Vannette pointed out. “Allie has published a first-author paper and co-authored two additional papers on how soil microbial communities are shaped by soil characteristics and plant species Allie has taken an active role in mentoring students in our lab. She has worked closely with and trained at least five undergraduate students in techniques ranging from DNA extraction and library prep, isolating and identifying soil bacteria, bioinformatics analysis and root imaging analysis. She has accompanied students to national meetings and supported their career goals even after they had left the lab.“

Vannette, who joined the UC Davis Department of Entomology and Nematology in 2015 after serving as a postdoctoral fellow at Stanford University’s biology department, also praised Allie for “taking an active role in mentoring students in our lab. She has worked closely with and trained at least five undergraduate students in techniques ranging from DNA extraction and library prep, isolating and identifying soil bacteria, bioinformatics analysis and root imaging analysis. She has accompanied students to national meetings and supported their career goals even after they had left the lab.”

“Allie has not only strong academic achievements, excellent leadership ability and but also the ability to translate these skills into meaningful research, impactful mentoring, and effective recruitment and retention of underrepresented students,” Vannette said. “Allie has accomplished a lot here at Davis and I am excited to watch her career unfold. Her achievements have been recognized with a prestigious NSF Postdoctoral fellowship.”

Born in Stockton but raised in Houston, Allie remembers how her mother, a registered nurse, “imparted on me the importance of education from a young age and did a lot to make sure I had access to the best public educational opportunities Houston had to offer.

“I am the first to go to graduate school and will be the first doctor in the family, although not the type they likely expected,” she quipped. “I’ve always been interested in the natural world and participated in science fairs growing up. My first project was a survey of all the bugs in my front yard. My mom and I collected, identified, and mounted them. She told me that she could always find me in some mud or looking under a rock or collecting snails. I always had an interest in the environmental field–it just took a little nudge from amazing mentors for me to pursue it.”

Allie received her bachelor’s degree in biology in 2013 from Howard University, Washington, D.C., where she submitted her honors thesis: “Elemental Defense in Alyssum murale: Effects on Plant-Herbivore Interactions.” She holds a master of science degree in soil science in December 2015 from Texas A&M (TAMU), where she presented her thesis on “Phytoremediation of Hydrocarbon-Contaminated Soil Using Phenolic-Exuding Horticultural Plants.”

At TAMU, Allie designed greenhouse experiment to identify rhizosphere microbial composition of horticulture plants growing in soil contaminated with polycyclic aromatic hydrocarbons.

The UC Davis doctoral student co-authored “Organic Management Promotes Natural Pest Control through Altered Plant Resistance to Insects,” published May 15 in the journal Nature Plants, with Vannette and several other co-authors.

Igwe served as the lead author of the Igwe-Vannette research, “Bacterial Communities Differ Between Plant Species and Soil Type, and Differentially Influence Seedling Establishment on Serpentine Soils,” published June 26, 2010 in the journal Plant and Soil.

At UC Davis, Igwe has helped other students succeed. She served as a teaching assistant from September 2016 to- December 2019 in the UC Davis Career Discovery Group. She mentored a group of 10-20 freshmen in career exploration activities and professional communication. In addition, she recruited industry professionals to participate in student networking events, and coordinated on-site visits with working professionals for career exploration trips. Igwe also was a success coach in the UC Davis Success Coaching and Learning Strategies for a year.