Barrett, The Honors College Thesis/Creative Project Collection
Barrett, The Honors College at Arizona State University proudly showcases the work of undergraduate honors students by sharing this collection exclusively with the ASU community.
Barrett accepts high performing, academically engaged undergraduate students and works with them in collaboration with all of the other academic units at Arizona State University. All Barrett students complete a thesis or creative project which is an opportunity to explore an intellectual interest and produce an original piece of scholarly research. The thesis or creative project is supervised and defended in front of a faculty committee. Students are able to engage with professors who are nationally recognized in their fields and committed to working with honors students. Completing a Barrett thesis or creative project is an opportunity for undergraduate honors students to contribute to the ASU academic community in a meaningful way.
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- Creators: School of Life Sciences
Due to complex requirements and relationships found in terrestrial soil environments, less than 2% of bacteria has been cultured using traditional cultivation methods. The soil substrate membrane system (SSMS) is a method designed to overcome these limitations by incorporating the environmental soil as substrate. This work examines the improvements achievable through SSMS in combination with two variables known to affect microbial growth: microaerophilic conditions and vitamin availability, on Peruvian peatland soils of varying nutrient levels; poor (San Jorge), intermediate (Quistococha), and rich (Buena Vista). First, a preliminary study was performed to enhance the knowledge of SSMS applications. Following, soil samples were pre-incubated according to their treatments and inoculated onto membranes for 3 weeks. New membranes were inoculated from the first membrane's enrichment and incubated for 2 weeks. Verified microcolonies were transferred onto dilute media (dR2G 1:5 or RAVAN) through direct streaking and spreading of dilutions (10-3, 10-5, 10-7). Colony appearance was monitored with colonies being isolated and purified. Buena Vista produced the largest, most diverse microcolonies as well as the most isolates. Quistococha produced the fewest microcolonies and isolates and was the only Peatland with increased success rates in the control group. Nearly a 4:1 recovery of isolates was observed for Buena Vista's and San Jorge's treatment groups compared to their control groups. With nearly 300 isolates in isolation and sequencing, it can be concluded that SSMS improves the recovery of terrestrial bacteria, and ongoing work aims to identify the recovered isolates.
Tropical peatlands play a critical role in global carbon storage and greenhouse gas flux, yet the role of microbial communities in these ecosystems remains poorly understood. Methane-oxidizing bacteria (MOB) are considered an efficient biological filter for methane and can mitigate its release into the atmosphere, facilitating an ecosystem’s capacity to become a net sink. Prokaryotic gene amplicon surveys targeting a unique biomarker instead of a universal one (i.e., 16S rRNA) can reveal a more comprehensive analysis of microbial communities with ecological functions (i.e., methanotrophy). The alpha subunit of particulate methane monooxygenase (pmoA) is commonly targeted as a phylogenetic biomarker for both aerobic and anaerobic MOB. Here, we tested three different primer sets and investigated their ability to assess methanotrophic diversity across three biogeochemically distinct tropical peatland sites in the Pastaza-Marañón foreland basin (PMFB) in western Amazonia. The results showed that sequencing using 16S rRNA and pmoA genes revealed differences in MOB taxonomic identification in 21 tropical peat soils. Beta diversity analysis of pmoA genes suggests that site location is not the main driver of differences in MOB community makeup. This work offers insight into the strengths and weaknesses of targeted gene amplicon surveys using 16S and pmoA from tropical peat soils as a case study.