Profiles of volatile compounds as microbial markers in applications of biosecurity and bioenergy
All organisms emit volatile organic compounds (VOCs) and profiling of volatiles (volatilomics) is finding diverse applications. Some VOCs are consistently present throughout the lifecycles of organisms, while other VOCs are biomarkers, quantifiable indicators of changes in physiological state or reflective of environmental stresses. This dissertation describes research into volatile biomarkers of different microorganisms in the context of biosecurity and bioenergy. Untargeted analyses of microbial biomarkers were accomplished using solid phase microextraction (SPME) coupled to gas chromatography-mass spectrometry (GC-MS). In the context of biosecurity, pathogenic bacteria can be used as the basis for a bio-terrorism attack. There is a need for deeper understanding of the chemical signatures of organisms, in particular when they infect individuals, and a need for methods for detecting these pathogens in the context of infections of humans. Current research has performed metabolite profiling of VOCs emitted in culture by surrogates for potential bacterial bioterrorism agents, Bacillus anthracis Sterne and Francisella tularensis novicida in conjunction with measurements of VOCs released by their fully virulent counterparts, F. tularensis SCHU S4 and B. anthracis Ames, both on the CDC category A bioterrorism and disease agent list. Methyl ketones, alcohols, esters, carboxylic acids, and nitrogen- and sulfur-containing compounds were attributed to the bacteria. The two genera showed distinct VOC profiles whereas the taxa within each genus showed subtler differences in VOC profiles. Growth phase influenced absolute and relative VOC abundances, indicating the potential for markers to discriminate growth phases. This in vitro determination of VOC profiles laid groundwork for non-invasive probing of bacterial metabolism.Towards bioenergy efforts, microalgae present a renewable alternative to producing biofuels. However, biofuels are more costly per gallon compared to non-renewable fossil fuels due to production and harvesting costs. Therefore, research driving increases in biomass production are of interest, specifically (1) better early-warning tools to anticipate and/or diagnose the presence of predators and (2) understanding algae-bacteria interactions, as they are challenging to manage and may help or harm algal productivity. Research towards part (1) aimed to better define the physiological state of algae ponds. A biofuel-relevant alga, Microchloropsis salina, was infected with a predator, the rotifer Brachionus plicatilis. SPME-GC-MS aided discovery of seven putative culture crash biomarkers, including carotenoid degradation products trans-β-ionone and β-cyclocitral, over several timepoints during active crashing of algal ponds that were not observed in healthy controls. These biomarkers offer potential as diagnostic tools to signal the need for crash mitigation strategies, as signals were detected before observed losses in algal cell density. Research towards part (2) aimed to detect and identify VOC biomarkers related to the micro-scale interactions of a model system of alga P. tricornutum and bacterium Marinobacter spp. 3-2. The presence of Marinobacter spp. 3-2, either in the form of live bacterial cells or sterile exudates, caused modest inhibition in growth rates of P. tricornutum. Substantial differences in VOC biomarker profiles were observed between 1) co-cultures of both organisms, 2) P. tricornutum exposed to Marinobacter spp. 3-2 exudates, and 3) Marinobacter spp. 3-2 exposed to P. tricornutum exudates, all relative to the VOC biomarker profiles of corresponding monocultures. Increasing the knowledge base of algae-bacterial interactions will enable a deeper understanding of the basic science of microorganism signaling.
Read
- In Collections
-
Electronic Theses & Dissertations
- Copyright Status
- In Copyright
- Material Type
-
Theses
- Authors
-
Reese, Kristen Leigh
- Thesis Advisors
-
Jones, A. Daniel
- Committee Members
-
Frank, Matthias
Spence, Dana
Blanchard, Gary
- Date
- 2020
- Subjects
-
Chemistry, Analytic
- Program of Study
-
Chemistry - Doctor of Philosophy
- Degree Level
-
Doctoral
- Language
-
English
- Pages
- 199 pages
- ISBN
-
9798662482210
- Permalink
- https://doi.org/doi:10.25335/rtw0-8712