Thesis
WILDFIRE IMPACTS ON SOIL MICROBIAL COMMUNITIES: POTENTIAL FOR DISRUPTIONS TO NUTRIENT CYCLING AND ANTIBIOTIC RESISTANCE GENE PROPAGATION IN BACTERIA
Washington State University
Master of Science (MS), Washington State University
01/2021
DOI:
https://doi.org/10.7273/000003352
Handle:
https://hdl.handle.net/2376/122597
Abstract
Wildfires naturally regulate nutrient cycling in ecosystems, but anthropogenic influences have caused wildfires to threaten the United States with increasing regularity and wildfires regularly impact soil bacteria. Wildfire-affected soils were studied with two primary objectives: 1) Determine the community composition in soils affected by wildfire intensities (i.e., low, moderate, high) to examine the impact on nutrient-cycling bacteria and 2) examine the effect of wildfires on the development of antibiotic resistance genes (ARGs) in soils. Objective 1 was achieved by characterizing soil bacterial communities in control (i.e., unburned) and burned soils using Illumina MiSeq 16S sequencing. Intensity (i.e., heat yield) was used rather than severity (i.e., burn impact) to examine the impact of fire temperatures on bacteria abundance. Six families and 17 genera were significantly (Spearman rs > |0.4|; p < 0.05) negatively associated with wildfire intensity and three families and six genera were significantly positively associated with wildfire intensity. Many of these taxa contain species that are known to be critical contributors to maintaining global nutrient cycles (i.e., nitrogen, sulfur, and phosphorus). Objective 2 was achieved by performing polymerase chain reaction and gel electrophoresis on isolated DNA. We targeted ARGs conferring resistance to common antibiotics (i.e., sul1, sul2, tetM, tetB, tetO, tetW, and ermF) as well as last resort antibiotics (i.e., mcr-1, optrA, fosA2, cfr). ARGs could increase after wildfires due to bacteria exposure to antibiotic fungal secondary metabolites, co-selection of ARGs on plasmids, increased rates of horizontal gene transfer, and exposure to antibiotics in runoff. No ARGs were detected in control soils. However, several ARGs were detected in burned soils. Sul1 was prominent in low and moderate intensity soils, while sul2 dominated in low intensity soils. TetW was prominent in moderate fire intensity soils. These results suggest that wildfires significantly alter microbial community structures and functions. A decrease in average relative abundance of nutrient cyclers after high intensity wildfires could slow ecosystem recovery, while the prominence of ARGs in wildfire affected soils suggests that wildfires increase ARG abundance. Increases in ARGs in the environment pose health risks to humans as the spread of antibiotic resistant infections grows.
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Details
- Title
- WILDFIRE IMPACTS ON SOIL MICROBIAL COMMUNITIES: POTENTIAL FOR DISRUPTIONS TO NUTRIENT CYCLING AND ANTIBIOTIC RESISTANCE GENE PROPAGATION IN BACTERIA
- Creators
- Tyler Alan Patrick
- Contributors
- Courtney M Gardner (Advisor)Amanda K Hohner (Committee Member)Indranil Chowdhury (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- Civil and Environmental Engineering, Department of
- Theses and Dissertations
- Master of Science (MS), Washington State University
- Publisher
- Washington State University
- Number of pages
- 132
- Identifiers
- 99900652204501842
- Language
- English
- Resource Type
- Thesis