Graduation Semester and Year
Spring 2025
Language
English
Document Type
Dissertation
Degree Name
Doctor of Philosophy in Quantitative Biology
Department
Biology
First Advisor
Dr. Woo-Suk Chang
Second Advisor
Dr. Alison Ravenscraft
Third Advisor
Dr. Luke O. Frishkoff
Fourth Advisor
Dr. Dylan B. Parks
Abstract
The increasing global regulations of glyphosate due to its possible carcinogenicity and environmental hazards have necessitated the search for alternative herbicides. Glufosinate-ammonium offers a sustainable attribute due to its low toxicity and limited reported herbicide resistance cases. Despite its increasing agricultural importance, very limited studies are done on its environmental impact, especially on the soil systems. This thesis examines the ecological behavior of glufosinate in soil, precisely focusing on its effect on the dynamics of soil microbiome and the potential use of Bradyrhizobium japonicum USDA110 for bioremediation by reversing the effect of microbial dysbiosis. A series of 30-day mesocosm studies were performed using different concentrations of glufosinate (43 and 86 fl. oz./A) to assess its impact on microbial diversity and pesticide degradation. High-throughput 16S rRNA gene sequencing shows a dose-dependent shift in soil microbiome towards glufosinate-tolerant taxa, notably Firmicutes, along with decreased species richness and evenness. Residual glufosinate measurement shows faster reduction in the two-time treatment group. This result complements the study from the metagenomics, suggesting adaptive enrichment of species, such as Bacillus and Pseudomonas, that are well known for glufosinate degradation. Weighted Gene Co-Expression Network Analysis (WGCNA) and co-occurrence network modeling show Pseudomonas, Hyphomicrobium, and Streptomyces as significant genera potentially contributing to accelerated glufosinate degradation.
A parallel experiment suggests the bioremediation capabilities of B. japonicum USDA110 in the presence of glufosinate. Additionally, a comparative study was performed to see the effect of microbial activity on glufosinate reduction in soil by autoclaving soil. The results indicate improved glufosinate degradation and microbial stability in the soil inoculated with the bacteria. Furthermore, inoculation helped with the preservation of phylogenetic diversity and Proteobacteria abundance. This suggests improved stability and partial reversal of glufosinate-induced microbial dysbiosis.
Keywords
Pesticide, Glufosinate, Soil Microbiome, Bradyrhizobium japonicum USDA110, Bioremediation, Network Analysis
Disciplines
Environmental Microbiology and Microbial Ecology
License
This work is licensed under a Creative Commons Attribution-NonCommercial-No Derivative Works 4.0 International License.
Recommended Citation
Das, Sarobi, "IMPACT OF GLUFOSINATE ON SOIL MICROBIAL COMMUNITY DYNAMICS" (2025). Biology Dissertations. 226.
https://mavmatrix.uta.edu/biology_dissertations/226